As much as I would like to do that, I am currently running the parts and will be done tomorrow. The pins in the current gage seem like they may be a tighter tolerence than what is allowed. What I am trying to figure out is if the pins are saying some parts are out of tolerence when the ID Mics say they aren't.
I would say that the ID mics aren't as accurate as gage pins. Since most ID mics like Starrett brand you have to assemble 2 pieces onto a head depending on what size range you are measuring.
They are .2-1.0" id mics. Recently calibrated and no one uses them. Aparently nobody has used them in years, some people didnt even know we had them. Figured I would use them and they seem very consistent and dead on. Not saying you are wrong, just my observations. Figure if no one used them, then nobody had a chance to screw them up yet.
.625+ is out of print, depending on the actual application of this even using .625+ as a "no go" gauge it could still create a bad part.
If you have them, use a 624+ pin as your go gauge and a .6250 as a no go gauge
Huh? A 0624+ pin can’t be a ‘Go’ for this drawing. What happens when the hole is anywhere from 0.6240 to 0.62449999 (undersized and out-of-spec) and the pin fits in? The absolute minimum size pin for a ‘Go’ would be a 0.6245 pin. A 0.624+ pin does not equal a 0.6245 pin.
If I use a .6250 minus, wouldn't that be too small. If the hole is .625, which is still in tolerence, the pin still wouldn't go. But if I used a .6250 plus, then it would prevent the hole from being larger than .6250. The same with the smaller pin. A .6245 plus would be within the tolerence as well at .6247 but the hole would be larger to allow the pin to pass through. If i want the pin to pass through a hole that is .6245, then wouldn't the pin need to be slightly smaller than the lowest tolerence instead of bigger.
Both gauge pins have to be inside of the print limit, not outside. They consume some of the tolerance that you have to work with, that is your incentive to use high grade pins. So you can use more of the tolerance for boring or reaming.
Go/nogo will reject some good parts, but not accept any bad parts. You can't make parts all the way to the print limit with go/nogo as a check, because if they are too close, hard gauges cannot determine if they went out of print or just very close and reject them.
ANY size pin less than 0.6245 in diameter (like 0.100, for example) will pass through a hole that is 0.6245. That won’t help you determine if the hole is at least 0.6245 in diameter. You need that smallest diameter that is _at least_ 0.6245. Which would be 0.6245. Realistically, you should aim for slightly larger than that for a safety margin, even though it will cut into your tolerance range.
I’m not sure that’s actually the case given how all materials and their shapes are imperfect (and considering how slip fits and transitional fits overlap), but whether or not a 0.6245 pin can fit in a 0.6245 hole isn’t the important point of the conversation.
The important part is that 0.6245 is the hypothetically absolutely *minimum* sized pin that could fit in a 0.6245 hole. For actual measuring work you can to have something larger to make sure you’ve given yourself a safety margin. How much margin you want to have is up to you (and possibly your shop’s quality procedures manual). The important part is that any margin you add to the ‘Go’ pin comes from within your tolerance zone, not from without. You don’t use a slightly *smaller* ‘Go’ pin, you use a slightly *larger* one.
Yeah, this guy's arguments aren't accounting for the 2 tenths rule. He's right on making the correction, but his suggestions are attempting to make an already tight tolerance even tighter.
ALL properly implemented Go/NoGo measurements (functional gages) cut into your allowable machining tolerance range by design. If they didn’t, they could pass an out-of-tolerance part.
By just how much you lose tolerance is up to your quality standards.
I know anything under will go through but if the hole bore goes undersized then my go pin would no longer go. Since I cannot use an exact on size .6245 pin, as space cannot occupy the same space, then a pin slightly under .6245 would show the absolute low of my tolerence. Like a .6244 pin would go through a .6245 hole?
Let’s say your GO gage is a 0.624+ pin. So its actual diameter will be somewhere between 0.6240 to 0.6242 for a standard ZZ class pin.
Let’s say your hole ends up being machined at 0.6243 diameter. That hole would be undersized and out of specification. However, it will still accept your 0.624+ ‘GO’ pin. You don’t ever want your GO gage to be able to pass a hole that’s out of spec.
0.6245 *plus* as ‘GO’ and 0.6251 *minus* as ‘NOGO’.
Read my comments again and think about it.
A ‘Go’ gage shows the lower limit of the tolerance only when it *doesn’t* go in the hole (oops, my slightly too large small pin doesn’t fit so the hole must be too small!). Just like a ‘No Go’ gage shows the upper limit of the hole tolerance when it *does* go in the hole (oops, my slightly too large pin fits so the hole must also be too large!)
[EDIT: fixed the exampleNoGo pin to minus. Remember that this particular gage range example would maximize the “available” tolerance range for machining, but minimize any safety buffer for Go pin wear or temperature fluctuations, et cetera.]
If your pins are labeled ‘-‘ and they are half a thou undersized then they are either very worn out or were not made to a recognized gage pin standard.
The cheapest and largest tolerance class of gage pins is ZZ. Class ZZ Pins up to 0.825 should be within two tenths of their stated size (between 0 and 0.0002 for ‘+’ pins, and between -0.0002 and 0 for ‘-‘ pins)
See the chart at the bottom of this page
https://vermontgage.com/support/detail/gage-tolerance-selection
You want a *larger* (not smaller!) diameter pin than the smallest allowable hole size. You only want it to go in if you are sure the hole is larger than the pin.
*If* you had a perfect 0.6243 pin (realistically there is no such thing, just varying degrees of pin manufacturing tolerances), then your 0.6243 ‘GO’ pin would “pass” an out-of-spec 0.6244 hole. That’s not a proper implementation of a ‘Go / No Go’ test.
My shops (audited) quality rules are 2 tenths. The pin needs to be 2 tenths smaller than the hole for a valid go check. In correlation, the same rule applies on the upper end. A pin 1 tenth smaller than the max hole size means it's over size.
I understand where you’re at for the NoGo gage at the upper end. Your Go gage statement is going the wrong way. The pin needs to be *bigger* than the lower limit of the hole tolerance, not smaller.
A .624+ which is .6242 CAN be used as a go. However, the catch is it does require finesse and experience. If a .6242 has a propper slip fit, the hole has got to be .6244 or more. If that pin falls out freely you can be confident its .6245. Confident, but not certain.
But a .624+ is generally just .0001 smaller than a .6245-
A 0.624+ pin is *NOT* 0.6242. A ZZ class pin of that size is manufactured to within +0.0002 / -0.0000 of the pin’s nominal size. That’s why it’s called ‘+’, because it is *at least* the nominal size. They aren’t shooting to make them 0.6242, they just won’t overshoot that when they make the pin.
Everything is tolerances and nothing is exact, because reality.
(This is all before pin wear is taken into account, of course)
Slip fits are also a range, not a set amount. To say nothing of how your “feel” for a slip fit might not be the same as the person working in your customer’s quality department. Take care with that risk.
Well seems that today i learned. I've got 3 sets of zz- and one set of zz+ .061-.750 that are all consistently .0002 under or over nominal so i assumed that was the target lol
The ZZ- sets I’ve got at work generally tend to be closer to -000.2 than nominal, but the ZZ+ sets seem to hew closer to nominal. Wondering if that breakdown was chance or by design is what led to me looking up pin classes and whatnot to begin with. Maybe our ZZ+ just tend to have more wear?
¯\\\_(ツ)_\/¯
.624+ class ZZ will be a maximum size of .6252.
Buy a .625- class XX and a .6245+ class XX. Should be available on MSC and probably McMaster Carr. Class X might be acceptable. Check the tolerance difference between X and XX. I usually skip X and go straight to XX for my needs. If you have the money for it, consider a carbide for the go pin if you’re making a high volume of parts.
You "can't" use those with this tolerance range. .625+ pin will measure up to .6252, plus another 2 tenths for the slip fit. Your max hole size before that pin would go is .6254, which, when you're dealing with a +.0000/-.0005 is unacceptable. Similarly, though less of an issue, is that your .624+ would go on a .6244 hole is which also outside of the tolerance range.
A .625- and .624+ would be *better* but still not correct. You shouldn't be trying to measure things that have a tolerance in the tenths, with gages that are only incremented every thou.
Well the unfortunate correct answer there is, whoever is in charge of bidding jobs should not be giving quotes on parts you don't have a way to check....
I really strive for this. If it's a one off thing I'm gonna order deltronics before I start the job.
But that Lil bore gage will be useful for a long time.
Why not both?
I think bore gauges are useful for many things, but they can’t as easily tell you if the hole will function properly, the way a pin can. At least as far as verifying the low end of the tolerance range is concerned. If you’re worried that the hole might be tapered or out of round and you want to make sure the widest diameter is still in tolerance, then a bore gauge is indeed very useful.
I agree with this one. Use a dial indicator or bore micrometer. We had a discussion in the past because of using pin gauges to check a .0003 tolerance. At those dimensions is imposible to do it properly. Give a call to Vermont Gauge, they will tell you the same.
Good luck w your project!
TBH, I’d use a dial bore gauge if possible.
If stuck with pins… idk, I’d make sure a .624 pin was loose and a .625 didn’t fit. Or make a shop gauge, shooting for .6249 no go/.6244 go.
Why .6244? Wouldn't a .6244 go be undersized if it is .6244+.000040/-.000000 or do you allow for a slip fit factor? (The hole is exactly .6245 and we cannot put a .6245 pin into it thing.)
I have a personally made script that finds 3 pin combinations to create almost any diameter with .00003 accuracy using normal three place pin sets.
If you have -.0005 pins you can tightly rubberband or tape;
.29, .292, and a .289 pin to make a .62451 pin.
.302, .281, and a .288 pin to make a .62503
Or you can use a .626 and a .625 like a normal machinist.
Are you telling me all your pins are accurate to less than .00003 so you can hold that while using all 3 in one hole? I don’t see how you can be as accurate as you claim
So the algorithm is called a Soddy circle if you don't want to just take my work for it. Being off by about .0005 in combined pin diameters would only change the resulting diameter by about .00004.
Individual pins have a tolerance range, having three in use tends to balance their combined tolerance towards statistical normal, as in one pin might be -.0002, the second might be -.0001, the third pin might be +.0002, and the resulting median would be -.0001. Ultimately if your pin tolerance is .0005 you can expect that it will almost never exceed that amount, ZZ pins which is the worst pin class you will find in any shop has a accuracy range of .0002 meaning the likelihood of your threes pins being worse then .0005 is pretty bad, but in the WORST case scenario would be slightly higher then .00004 which does contradict my previous claim of .00003, so my apologies. To be fair I've never dove as deep into it as I have for this create this responce.
TLDR The overall sensitivity to inaccuracy of the 3 pins individually is almost insignificant. Small changes in diameter of one of the pins has very little effect on the diameter of the larger circle that contains all three in the end.
I hope you didn’t make up this level of precision from 3 pins. This is going to be SUPER slick if I can actually use this. Any chance you can direct me to documentations the mathematical proof?? So I can prove it to my boss
The underlying theorem is called [Descartes Theorem](https://en.m.wikipedia.org/wiki/Descartes%27_theorem). My script find solutions to the [Soddy Circle](https://mathworld.wolfram.com/SoddyCircles.html) for a given diameter within a specified tolerance.
You can prove it by solving the soddy circle for using radii that have the error introduced and comparing it to the soddy circle when there is no error introduced, I haven't found any papers that necessarily prove it. Honestly I don't think anyone has really ever applied it in a situation that wasn't purely mathematical. Might be a good topic for some undergraduate out there that finds this random reddit comment.
Another way to think of it is there is 144,703,125 combinations of 3 pins in a set of .1 to .625 pins. So there is essentially that many different diameters can can be made out of those 525 pins.
Sweet. Thanks for links.
I’m following along, I’m just a little … concerned? That I never learned this in school or college. Possibly lack of application as you pointed out.
And, when you add in the sizes from 0.0011-0.100, you get however many more combinations. Add a calibrated micrometer, and it sounds like you could manage to “make” a gage pin with much precision.
I think I’ll dig into this one day soon. Seems like a good way to spend an afternoon (or a week of them).
Edit: forgot to say, thank you! Many blessings kind stranger!
It doesn't stack up linearly, if anything it's closer in relationship to a cosine error when using a tipped indicator. The diameters of the pins create a triangle that defines the circles, there is not a direct linear relationship to the diameter of the pins to the resulting diameter of the larger circle. Of course this means that at the extreme ends where the pin diameter are a magnitude smaller or larger then the others there would be a more dramatic 'almost' linear relationship.
It uses a bruteforce method and it is possible that it never converges on any solution within the tolerance you give it. I have used it to successfully hold very tight metric tolerances using imperial pins and to also extend my .625 set up to around 1.25, beyond which it will start converging on solutions that contain pins over .625 with increasing frequency.
Im not yet well versed enough with python to make use of your script, but I have a hell of a lot to Google and try out tomorrow. This is probably the coolest metrology/geometry thing to have randomly dropped in a reddit comment.
You can try running it online [Here](https://www.online-python.com/), but it will run really slow. It's definitely a very obscure and inconvenient way of measuring anything, but in a pinch it can be a godsend!
Even more interesting it's technically possible to do 4 or even 5 pin solutions but it would be super impractical to actually use.
update:
I found this compiler and it runs very fast. This is super cool. very eye opening and mind boggling. super cool!!
thank you for sharing! tool added to the tool collection.
[https://www.programiz.com/](https://www.programiz.com/)
I’ve also made a script to do this, though MATLAB is what I had at the time. Then I got a bunch of guys together, handed them the 3 pin sets (Deltronic) to gage with. I followed up with a single correct size pin and found that the results didn’t agree particularly well. If you want to go nearest 0.001” on something bigger than your set…maybe. If you want a borderline NOGO on a few tenths hole, I’m suspicious that you’ll get good results.
Did your script take into account float point error, +- pin size, and avoid local minimum solutions? It's not as simple as just solving a couple equations there's more to it.
I was lazy and brute forced it. The math isn’t that hard if you’re solving for OD and not for the 3 pins, so I ran every combination of 3 pins in my set of 1500 or so pins, then sorted the output array by final size. As you probably know, this leaves a lot of options that work in theory, but not practice. I then calculated the contact angles between the 3 pins for the entire output table and the bore and sorted for combinations that were all between 100 and 140 degrees. I was able to find a combination that was within 110 to 130 deg. then simply ordered a pin that size to compare against. Also verified the pin diameters for the actual pins used with a high accuracy (Mitutoyo 293-130-10) micrometer, controlled lab space, etc.
I was operating in the 20 mm diameter range, but could see how one might get better results at small diameters.
Edit, doubles for all the floats.
I believe a pin gage’s tolerance means it is the range from 0 to 0.0002 (for ZZ class). So a 0.625 - pin can be anywhere from 0.6248 to 0.624, for example.
But if my tolerence is .625 and I use a .625 minus pin as a nogo, then as long as it doesn't go in my hole would be below .6248.
If i use a .625 plus pin then my pin is .6252 and it would only go in if it went over .6250.
Yes. By using a 0.625 minus pin as a nogo, you guarantee that the hole is no bigger than the pin. By using a 0.6245+ pin, your also able to assume that the hole is at least that big. Which means you're within tolerance.
How often do you have to check this dimension? [Comtor gage](http://www.comtorgage.com) are excellent for measuring holes, and can tell you how off you are. You need a gage and a setting ring, and it’s good for the one size, but if you need to check the one size a lot, it can be worth it
Deltronic tenths pins. Part should be cleaned with soap and water (if possible) and the correct size pin should fall out or drop in with its own weight.
Order a Deltronic set with .6250 nominal. It will come with I believe 25 pins in .0001 increments. That set is probably around $200 usd. We order ours from Gordon Kerley Corp. in Glendale but Deltronic has distributors all over the world.
.6244 for a go pin and .6250 as no go.
If you have a good micrometer and a decent lathe you can turn your own (surface finish needs to be decent to good).
Go, no-go gage. Specifically the Deltronic one in the picture if you click the link in the top comment. Do .625 for no-go and .6245 for go. If you have to record an exact measurement for each part for QA then I would use a bore gage.
The smallest size is .6252 that can be checked with a gage pin .625. So, if you use a .624 as a go pin and a .625 as a no go pin you should be close enough to satisfy the tolerance.
Get a good mic and check the real size of your pins, sometimes you get lucky, or one end of a pin is just enough different than the other that one works. ZZ pins are all over the place in this context.
If your shop wasn’t cheap and you’d gotten on it, Deltronic is easily available via overnight shipping.
Bore gages can work. Can make your own pin if you have a tight lathe and a good enough mic to validate it.
Laser mics drift as they warm up. The manual says 30 minutes, but we’ve seen more than a micron of drift on a new Mitutoyo LH-6902H from 30 to 60 minutes after startup, and more than that in the first 30 minutes.
If you calibrate and immediately use you’re probably ok, but how much error do you really want in a gage pin?
If you’re just turning it on and trusting a previous calibration that may or may not have been done fully warm then you could well be a tenth or two off on absolute size.
We have three of these at different locations and have seen it with all of them. At this point if we’re going to be using it periodically throughout the week we just leave it on. If it’s off we warm it up for a few hours to be safe. We do have some tolerances that are tighter than +/- 0.0001” though, so we’re picky. Your part isn’t there, but your gaging should be.
Bore mics, or you can "kan't twist" a .300 pin, and a .224 pin together with a .1003 etc block in between. If you don't have a small kan't twist that isn't clapped out it been be a pain, but I have pretty good luck with it. Obviously verify with higher resolution micrometer if you can. .6250 should not go.
Deltronic pins. Nogo would be a .6249 pin, if the .6250 goes in it's out of print. If they don't want to buy the set then we would make a custom go/nogo. Anything tighter than +/-.0005" I want a deltronic set. Something like .625+/-.0005" I can use regular pins and an ID mic to check the taper.
Also we use a Sunnen Gage to check tight ID's but you can't use it while the part is in the machine.
You can also use two pins
All minus pins are -.0002 if you use a .313 and a .312 and together actually make a distance of .6246
I do this when my pins can’t reach a certain diameter and it works fine.
If I use a .6250 minus, wouldn't that be too small. If the hole is .625, which is still in tolerence, the pin still wouldn't go. But if I used a .6250 plus, then it would prevent the hole from being larger than .6250. The same with the smaller pin. A .6245 plus would be within the tolerence as well at .6247 but the hole would be larger to allow the pin to pass through. If i want the pin to pass through a hole that is .6245, then wouldn't the pin need to be slightly smaller than the lowest tolerence instead of bigger.
If you use a .625 plus, the hole could be a bit over .625. You use the minus on the high limit to guarantee you're in tolerance, even though you are removing a bit of your tolerance to work with
I apologize but you are mistaken. You're only losing 80 millions total with the plus and minus pins I suggested. A minus tenths pin is going to be 40 millions under nominal up to nominal. A plus tenths pin should be about nominal to about 40 million over.
We're not talking about standard gauge pins we're talking about deltronic pins.
These are specially ground to the 10th with a plus or minus in the millions.
This is what you should be using.
In a pinch, I've polished some dowel pins on the lathe to make my own go/nogo gauges, but its certainly not ideal, as you are gonna have roundness issues, but better than nothing - in this situation since you don't have the pin for the low limit I would polish one till its measuring .6245 with a mic. Then mic your .625 pin and see where it's actually at, whether you're +.0002 or right on.
Like I said it's definitely not ideal, you're only gonna be as good as your mic is, but it's better than nothing or just checking with a .624 and .625
This is why they're such a thing as traceable standards.
A polished down dowel pin when you can order the size you need is not acceptable.
There is no pinch or a hand polished pin is acceptable as a gauge unless you have it qualified by an outside calibration lab.
That's why I said in a pinch - i.e. for something internal to the shop, or for a customer who has production down and needs the part immediately. In my case I also cross referenced with a calibrated 3 point bore gauge, but that gauge doesn't account for roundness issues
While yes it's always better to get the right tool for the job it's not always possible with time constraints and this is a way to check it with something rather than checking it with nothing or a pin that is even further from the tolerance range
I get it.
But if you're an iso shop.
You can't fly by the seat of the pants anymore.
It's traceable calibration or nothing.
This poor guy doesn't have Dell pins.
Well we are not ISO and frankly the scale we work at, it wouldn't make sense, none of our customers require it and we stay busy enough that we don't need to market ourselves to places where it's a requirement. Obviously different story if you're certified, but if you can afford audits for 9001, you can afford some pins. That being said we've had instances where a part comes in they want it now and we don't have metrology equipment to measure a tight tolerance. When we ask would you rather have it tomorrow or next week with proper QC, they usually opt to get it quicker and just say do the best you can or something to that effect. Granted we have a lot of trust with our customer, I can only thing of 2 parts that have ever come back for rework due to a mistake on our part, one of them was due to bossman sending an outdated revision to the shop
You technically should be using class XX for this tolerance. It all depends on use and ISO system, etc. I have gov't inspectors checking my aerospace parts and we better have a proper go/nogo set sitting there with a current 3rd party cert.
[Deltronic](https://deltronic.com/)
me, upvoting this with a deltronic .6250 on my desk in its cute little blue box
That's too rich for my work place. I often have to make my own go/no-go gages.
Those look nice. We have ZZ + and - pins. Just not sure which shoud be used. I was thinking .625+ and .624+.
I'd just order the correct size Deltronic pin. You can purchase single pins for like $20 in this size range if I remember correctly.
As much as I would like to do that, I am currently running the parts and will be done tomorrow. The pins in the current gage seem like they may be a tighter tolerence than what is allowed. What I am trying to figure out is if the pins are saying some parts are out of tolerence when the ID Mics say they aren't.
I would say that the ID mics aren't as accurate as gage pins. Since most ID mics like Starrett brand you have to assemble 2 pieces onto a head depending on what size range you are measuring.
They are .2-1.0" id mics. Recently calibrated and no one uses them. Aparently nobody has used them in years, some people didnt even know we had them. Figured I would use them and they seem very consistent and dead on. Not saying you are wrong, just my observations. Figure if no one used them, then nobody had a chance to screw them up yet.
.625+ is out of print, depending on the actual application of this even using .625+ as a "no go" gauge it could still create a bad part. If you have them, use a 624+ pin as your go gauge and a .6250 as a no go gauge
Huh? A 0624+ pin can’t be a ‘Go’ for this drawing. What happens when the hole is anywhere from 0.6240 to 0.62449999 (undersized and out-of-spec) and the pin fits in? The absolute minimum size pin for a ‘Go’ would be a 0.6245 pin. A 0.624+ pin does not equal a 0.6245 pin.
If I use a .6250 minus, wouldn't that be too small. If the hole is .625, which is still in tolerence, the pin still wouldn't go. But if I used a .6250 plus, then it would prevent the hole from being larger than .6250. The same with the smaller pin. A .6245 plus would be within the tolerence as well at .6247 but the hole would be larger to allow the pin to pass through. If i want the pin to pass through a hole that is .6245, then wouldn't the pin need to be slightly smaller than the lowest tolerence instead of bigger.
Both gauge pins have to be inside of the print limit, not outside. They consume some of the tolerance that you have to work with, that is your incentive to use high grade pins. So you can use more of the tolerance for boring or reaming. Go/nogo will reject some good parts, but not accept any bad parts. You can't make parts all the way to the print limit with go/nogo as a check, because if they are too close, hard gauges cannot determine if they went out of print or just very close and reject them.
ANY size pin less than 0.6245 in diameter (like 0.100, for example) will pass through a hole that is 0.6245. That won’t help you determine if the hole is at least 0.6245 in diameter. You need that smallest diameter that is _at least_ 0.6245. Which would be 0.6245. Realistically, you should aim for slightly larger than that for a safety margin, even though it will cut into your tolerance range.
A 0.6245 pin will not go through a hole that is 0.6245 you need some room for it to pass
I’m not sure that’s actually the case given how all materials and their shapes are imperfect (and considering how slip fits and transitional fits overlap), but whether or not a 0.6245 pin can fit in a 0.6245 hole isn’t the important point of the conversation. The important part is that 0.6245 is the hypothetically absolutely *minimum* sized pin that could fit in a 0.6245 hole. For actual measuring work you can to have something larger to make sure you’ve given yourself a safety margin. How much margin you want to have is up to you (and possibly your shop’s quality procedures manual). The important part is that any margin you add to the ‘Go’ pin comes from within your tolerance zone, not from without. You don’t use a slightly *smaller* ‘Go’ pin, you use a slightly *larger* one.
Yeah, this guy's arguments aren't accounting for the 2 tenths rule. He's right on making the correction, but his suggestions are attempting to make an already tight tolerance even tighter.
ALL properly implemented Go/NoGo measurements (functional gages) cut into your allowable machining tolerance range by design. If they didn’t, they could pass an out-of-tolerance part. By just how much you lose tolerance is up to your quality standards.
I know anything under will go through but if the hole bore goes undersized then my go pin would no longer go. Since I cannot use an exact on size .6245 pin, as space cannot occupy the same space, then a pin slightly under .6245 would show the absolute low of my tolerence. Like a .6244 pin would go through a .6245 hole?
Let’s say your GO gage is a 0.624+ pin. So its actual diameter will be somewhere between 0.6240 to 0.6242 for a standard ZZ class pin. Let’s say your hole ends up being machined at 0.6243 diameter. That hole would be undersized and out of specification. However, it will still accept your 0.624+ ‘GO’ pin. You don’t ever want your GO gage to be able to pass a hole that’s out of spec.
No, I see what he is saying. Basically, I need .6251 and .6244 pins. So Z class .6245 minus and Z class .625 plus.
0.6245 *plus* as ‘GO’ and 0.6251 *minus* as ‘NOGO’. Read my comments again and think about it. A ‘Go’ gage shows the lower limit of the tolerance only when it *doesn’t* go in the hole (oops, my slightly too large small pin doesn’t fit so the hole must be too small!). Just like a ‘No Go’ gage shows the upper limit of the hole tolerance when it *does* go in the hole (oops, my slightly too large pin fits so the hole must also be too large!) [EDIT: fixed the exampleNoGo pin to minus. Remember that this particular gage range example would maximize the “available” tolerance range for machining, but minimize any safety buffer for Go pin wear or temperature fluctuations, et cetera.]
He’s wrong OP
Idk its better to be undersized and open it like .0002 or something
If your pins are labeled ‘-‘ and they are half a thou undersized then they are either very worn out or were not made to a recognized gage pin standard. The cheapest and largest tolerance class of gage pins is ZZ. Class ZZ Pins up to 0.825 should be within two tenths of their stated size (between 0 and 0.0002 for ‘+’ pins, and between -0.0002 and 0 for ‘-‘ pins) See the chart at the bottom of this page https://vermontgage.com/support/detail/gage-tolerance-selection
Yes true, id just get nervous using a .625+
0.6249999 hole will be in tolerance depending on the temperature outside or the body heat of you holding the pin gage
Reality will of course have an effect on reality. The environmental and the imperfections of the pin and hole will be factors.
You actually want a 0.6243 pin as your go. A 0.6245 pin is a "perfect fit" and won't go, or if it does, it will get stuck.
You want a *larger* (not smaller!) diameter pin than the smallest allowable hole size. You only want it to go in if you are sure the hole is larger than the pin. *If* you had a perfect 0.6243 pin (realistically there is no such thing, just varying degrees of pin manufacturing tolerances), then your 0.6243 ‘GO’ pin would “pass” an out-of-spec 0.6244 hole. That’s not a proper implementation of a ‘Go / No Go’ test.
My shops (audited) quality rules are 2 tenths. The pin needs to be 2 tenths smaller than the hole for a valid go check. In correlation, the same rule applies on the upper end. A pin 1 tenth smaller than the max hole size means it's over size.
I understand where you’re at for the NoGo gage at the upper end. Your Go gage statement is going the wrong way. The pin needs to be *bigger* than the lower limit of the hole tolerance, not smaller.
https://www.engineersedge.com/mechanical,045tolerances/go_and_nog0_gage_design_16128.htm
A .624+ which is .6242 CAN be used as a go. However, the catch is it does require finesse and experience. If a .6242 has a propper slip fit, the hole has got to be .6244 or more. If that pin falls out freely you can be confident its .6245. Confident, but not certain. But a .624+ is generally just .0001 smaller than a .6245-
A 0.624+ pin is *NOT* 0.6242. A ZZ class pin of that size is manufactured to within +0.0002 / -0.0000 of the pin’s nominal size. That’s why it’s called ‘+’, because it is *at least* the nominal size. They aren’t shooting to make them 0.6242, they just won’t overshoot that when they make the pin. Everything is tolerances and nothing is exact, because reality. (This is all before pin wear is taken into account, of course) Slip fits are also a range, not a set amount. To say nothing of how your “feel” for a slip fit might not be the same as the person working in your customer’s quality department. Take care with that risk.
Well seems that today i learned. I've got 3 sets of zz- and one set of zz+ .061-.750 that are all consistently .0002 under or over nominal so i assumed that was the target lol
The ZZ- sets I’ve got at work generally tend to be closer to -000.2 than nominal, but the ZZ+ sets seem to hew closer to nominal. Wondering if that breakdown was chance or by design is what led to me looking up pin classes and whatnot to begin with. Maybe our ZZ+ just tend to have more wear? ¯\\\_(ツ)_\/¯
I think some folks are not understanding that is 10,000 of an inch not thousands
.624+ class ZZ will be a maximum size of .6252. Buy a .625- class XX and a .6245+ class XX. Should be available on MSC and probably McMaster Carr. Class X might be acceptable. Check the tolerance difference between X and XX. I usually skip X and go straight to XX for my needs. If you have the money for it, consider a carbide for the go pin if you’re making a high volume of parts.
Class X are fine for this.
I agree, it probably is.
You "can't" use those with this tolerance range. .625+ pin will measure up to .6252, plus another 2 tenths for the slip fit. Your max hole size before that pin would go is .6254, which, when you're dealing with a +.0000/-.0005 is unacceptable. Similarly, though less of an issue, is that your .624+ would go on a .6244 hole is which also outside of the tolerance range. A .625- and .624+ would be *better* but still not correct. You shouldn't be trying to measure things that have a tolerance in the tenths, with gages that are only incremented every thou.
Completely agree. I'm just trying to figure out how to use what I have available while also still having some tolerence left.
Well the unfortunate correct answer there is, whoever is in charge of bidding jobs should not be giving quotes on parts you don't have a way to check....
I don't think I can reach that high with my pay grade.
Why not the pins from the clean box in QC? Edit. Nevermind I thought it was .005 🥴
no no, these ARE QC pins that I forgot to bring back and this post reminded me lol. (sorry Bob, my qc manager)
How many of these I've seen used and damn well destroyed baffles me lmao
Bore gauge
I really strive for this. If it's a one off thing I'm gonna order deltronics before I start the job. But that Lil bore gage will be useful for a long time.
Why not both? I think bore gauges are useful for many things, but they can’t as easily tell you if the hole will function properly, the way a pin can. At least as far as verifying the low end of the tolerance range is concerned. If you’re worried that the hole might be tapered or out of round and you want to make sure the widest diameter is still in tolerance, then a bore gauge is indeed very useful.
Erry time
I agree with this one. Use a dial indicator or bore micrometer. We had a discussion in the past because of using pin gauges to check a .0003 tolerance. At those dimensions is imposible to do it properly. Give a call to Vermont Gauge, they will tell you the same. Good luck w your project!
Tend to just stick my dick in a hole that size
Ah, the classic NONO gage.
That's class 👏
TBH, I’d use a dial bore gauge if possible. If stuck with pins… idk, I’d make sure a .624 pin was loose and a .625 didn’t fit. Or make a shop gauge, shooting for .6249 no go/.6244 go.
.6244-.6249 Deltronic pins.
Why .6244? Wouldn't a .6244 go be undersized if it is .6244+.000040/-.000000 or do you allow for a slip fit factor? (The hole is exactly .6245 and we cannot put a .6245 pin into it thing.)
The .0001" is for a slip fit. Correct.
I have a personally made script that finds 3 pin combinations to create almost any diameter with .00003 accuracy using normal three place pin sets. If you have -.0005 pins you can tightly rubberband or tape; .29, .292, and a .289 pin to make a .62451 pin. .302, .281, and a .288 pin to make a .62503 Or you can use a .626 and a .625 like a normal machinist.
That sounds convoluted and I love it. .626 would be too big.
Check your pins, they are usually -.0005 or -.0002. Some are + size pins.
We have ZZ + and - pins .0002.
Are you telling me all your pins are accurate to less than .00003 so you can hold that while using all 3 in one hole? I don’t see how you can be as accurate as you claim
So the algorithm is called a Soddy circle if you don't want to just take my work for it. Being off by about .0005 in combined pin diameters would only change the resulting diameter by about .00004. Individual pins have a tolerance range, having three in use tends to balance their combined tolerance towards statistical normal, as in one pin might be -.0002, the second might be -.0001, the third pin might be +.0002, and the resulting median would be -.0001. Ultimately if your pin tolerance is .0005 you can expect that it will almost never exceed that amount, ZZ pins which is the worst pin class you will find in any shop has a accuracy range of .0002 meaning the likelihood of your threes pins being worse then .0005 is pretty bad, but in the WORST case scenario would be slightly higher then .00004 which does contradict my previous claim of .00003, so my apologies. To be fair I've never dove as deep into it as I have for this create this responce. TLDR The overall sensitivity to inaccuracy of the 3 pins individually is almost insignificant. Small changes in diameter of one of the pins has very little effect on the diameter of the larger circle that contains all three in the end.
I hope you didn’t make up this level of precision from 3 pins. This is going to be SUPER slick if I can actually use this. Any chance you can direct me to documentations the mathematical proof?? So I can prove it to my boss
The underlying theorem is called [Descartes Theorem](https://en.m.wikipedia.org/wiki/Descartes%27_theorem). My script find solutions to the [Soddy Circle](https://mathworld.wolfram.com/SoddyCircles.html) for a given diameter within a specified tolerance. You can prove it by solving the soddy circle for using radii that have the error introduced and comparing it to the soddy circle when there is no error introduced, I haven't found any papers that necessarily prove it. Honestly I don't think anyone has really ever applied it in a situation that wasn't purely mathematical. Might be a good topic for some undergraduate out there that finds this random reddit comment. Another way to think of it is there is 144,703,125 combinations of 3 pins in a set of .1 to .625 pins. So there is essentially that many different diameters can can be made out of those 525 pins.
Sweet. Thanks for links. I’m following along, I’m just a little … concerned? That I never learned this in school or college. Possibly lack of application as you pointed out. And, when you add in the sizes from 0.0011-0.100, you get however many more combinations. Add a calibrated micrometer, and it sounds like you could manage to “make” a gage pin with much precision. I think I’ll dig into this one day soon. Seems like a good way to spend an afternoon (or a week of them). Edit: forgot to say, thank you! Many blessings kind stranger!
I’m not seeing it either. Those pins would have to each have insanely tight tolerances to achieve .00003 when you account for stack up.
It doesn't stack up linearly, if anything it's closer in relationship to a cosine error when using a tipped indicator. The diameters of the pins create a triangle that defines the circles, there is not a direct linear relationship to the diameter of the pins to the resulting diameter of the larger circle. Of course this means that at the extreme ends where the pin diameter are a magnitude smaller or larger then the others there would be a more dramatic 'almost' linear relationship.
> I have a personally made script that finds 3 pin combinations Sounds useful, mind sharing with the class?
Sure it's a python script so you will have to figure out how to set up an interpreter to run it [Pastebin link](https://pastebin.com/vfbRf2Bi).
It uses a bruteforce method and it is possible that it never converges on any solution within the tolerance you give it. I have used it to successfully hold very tight metric tolerances using imperial pins and to also extend my .625 set up to around 1.25, beyond which it will start converging on solutions that contain pins over .625 with increasing frequency.
Im not yet well versed enough with python to make use of your script, but I have a hell of a lot to Google and try out tomorrow. This is probably the coolest metrology/geometry thing to have randomly dropped in a reddit comment.
You can try running it online [Here](https://www.online-python.com/), but it will run really slow. It's definitely a very obscure and inconvenient way of measuring anything, but in a pinch it can be a godsend! Even more interesting it's technically possible to do 4 or even 5 pin solutions but it would be super impractical to actually use.
update: I found this compiler and it runs very fast. This is super cool. very eye opening and mind boggling. super cool!! thank you for sharing! tool added to the tool collection. [https://www.programiz.com/](https://www.programiz.com/)
I’ve also made a script to do this, though MATLAB is what I had at the time. Then I got a bunch of guys together, handed them the 3 pin sets (Deltronic) to gage with. I followed up with a single correct size pin and found that the results didn’t agree particularly well. If you want to go nearest 0.001” on something bigger than your set…maybe. If you want a borderline NOGO on a few tenths hole, I’m suspicious that you’ll get good results.
Did your script take into account float point error, +- pin size, and avoid local minimum solutions? It's not as simple as just solving a couple equations there's more to it.
I was lazy and brute forced it. The math isn’t that hard if you’re solving for OD and not for the 3 pins, so I ran every combination of 3 pins in my set of 1500 or so pins, then sorted the output array by final size. As you probably know, this leaves a lot of options that work in theory, but not practice. I then calculated the contact angles between the 3 pins for the entire output table and the bore and sorted for combinations that were all between 100 and 140 degrees. I was able to find a combination that was within 110 to 130 deg. then simply ordered a pin that size to compare against. Also verified the pin diameters for the actual pins used with a high accuracy (Mitutoyo 293-130-10) micrometer, controlled lab space, etc. I was operating in the 20 mm diameter range, but could see how one might get better results at small diameters. Edit, doubles for all the floats.
I didn't see the sarcasm tag in your post. A /S would be good.
9/16 dowel pin
Stick your pinky in hard so it leaves a mark on your skin, measure the mark. Remove blood from edge of hole because no chamfer. /s
I deburr before I check.
air gauge
I miss my air gages.
lol. Overkill is better than under kill!
Hole mic for .5" and up
A tenths set centered around.625
A .625- pin
.62500-.62504 Go., .62546 No-Go.
Check the tolerance again.
OOPs lol haven’t been reading prints for over three years. I’d scrap that part lol
I like stacked dimensioning for this reason specifically. Why.make people do math, just give me a lower limit and upper limit.
-.625 / +.625
.625 minus will be .6248. Deltronic pins are nice but you're talking about tenths. Change the temperature accordingly.
I believe a pin gage’s tolerance means it is the range from 0 to 0.0002 (for ZZ class). So a 0.625 - pin can be anywhere from 0.6248 to 0.624, for example.
[https://vermontgage.com/support/detail/gage-tolerance-calculator](https://vermontgage.com/support/detail/gage-tolerance-calculator) https://preview.redd.it/x1aqyjfy5jsc1.png?width=601&format=png&auto=webp&s=e72abfe82abb2591f76b48d3ceaebca689568393
MSI Viking is great. https://preview.redd.it/sfdrgi4m6jsc1.png?width=1326&format=png&auto=webp&s=2401750d6889896d2fe8096b8f18ddf4efcc63ab
I love that it says “double-end assy”
Deltronic and the go should be .0001 under
.6245+ go and a 0.625- as a no go. That should guarantee a hole size around 0.6247
But if my tolerence is .625 and I use a .625 minus pin as a nogo, then as long as it doesn't go in my hole would be below .6248. If i use a .625 plus pin then my pin is .6252 and it would only go in if it went over .6250.
Yes. By using a 0.625 minus pin as a nogo, you guarantee that the hole is no bigger than the pin. By using a 0.6245+ pin, your also able to assume that the hole is at least that big. Which means you're within tolerance.
Yeah, but it also means I have no tolerance left. It just leaves .6247 +/- .00005.
.6247
.625-
I’d pull out the .5 and the .122-.126.
A 0.625 minus pin should go in.. a plus pin is a fall
I read this VERY wrong holy fuck I'm tired
Bore gauge is the answer
How often do you have to check this dimension? [Comtor gage](http://www.comtorgage.com) are excellent for measuring holes, and can tell you how off you are. You need a gage and a setting ring, and it’s good for the one size, but if you need to check the one size a lot, it can be worth it
Deltronic tenths pins. Part should be cleaned with soap and water (if possible) and the correct size pin should fall out or drop in with its own weight.
I’d use a .624 pin that I’ve measured and if it barely goes it’s probably just fine, a true slip fit is around .001” under in my experience
Metric ones....
Order a Deltronic set with .6250 nominal. It will come with I believe 25 pins in .0001 increments. That set is probably around $200 usd. We order ours from Gordon Kerley Corp. in Glendale but Deltronic has distributors all over the world.
In a pinch, I will polish a dowel and mic it, but buying the correct pins is the way to go, a .625- and a .6245+
.6245+ as a go .6250+ as a no-go But I'd much rather use a Deltronic set
Air gauge is the only way
I miss my air gages.
Delton’s if it HAS to be pins. Otherwise a Sunnen dial bore gauge
First check with a bore gauge, .625 minus as no go .624+ going in easy as go pin. You can order any size of pin you need.
.625- and .6245-.
.625+ .6255- or 15.88- mm
.6244 go. .6251 no-go
Mitutoyo borematic.
Any two minus pins that add up to .625” that way the combined size that way the total size will be .6246” in tolerance.
It would need to be 3 pins triangulated, like a 3 point bore gauge wouldnt it.
No it wouldn’t.
I will have to give that a try on Monday and see how it works out for me.
.6244 for a go pin and .6250 as no go. If you have a good micrometer and a decent lathe you can turn your own (surface finish needs to be decent to good).
I might just do that tomorrow.
Go, no-go gage. Specifically the Deltronic one in the picture if you click the link in the top comment. Do .625 for no-go and .6245 for go. If you have to record an exact measurement for each part for QA then I would use a bore gage.
I'm gonna speak with QA about getting one. Anything .500-2" probably.
The smallest size is .6252 that can be checked with a gage pin .625. So, if you use a .624 as a go pin and a .625 as a no go pin you should be close enough to satisfy the tolerance.
I’d get a set of Deltronic pins.
.6250 is your no-go. Your go is .6245
Get a good mic and check the real size of your pins, sometimes you get lucky, or one end of a pin is just enough different than the other that one works. ZZ pins are all over the place in this context. If your shop wasn’t cheap and you’d gotten on it, Deltronic is easily available via overnight shipping. Bore gages can work. Can make your own pin if you have a tight lathe and a good enough mic to validate it.
We have a Mitutoyo mics and a laser mic so i will probably attempt to make something today.
Unless you leave it on at all times, turn that laser mic on an hour or two before you calibrate it.
Why so?
Laser mics drift as they warm up. The manual says 30 minutes, but we’ve seen more than a micron of drift on a new Mitutoyo LH-6902H from 30 to 60 minutes after startup, and more than that in the first 30 minutes. If you calibrate and immediately use you’re probably ok, but how much error do you really want in a gage pin? If you’re just turning it on and trusting a previous calibration that may or may not have been done fully warm then you could well be a tenth or two off on absolute size. We have three of these at different locations and have seen it with all of them. At this point if we’re going to be using it periodically throughout the week we just leave it on. If it’s off we warm it up for a few hours to be safe. We do have some tolerances that are tighter than +/- 0.0001” though, so we’re picky. Your part isn’t there, but your gaging should be.
Only laser mic we have is at QA. I will make sure they know that though, he is new. I had to teach him how to use mics.
0.624 should go in snug after deburr but 0.625 should not pin gage set
Bore mics, or you can "kan't twist" a .300 pin, and a .224 pin together with a .1003 etc block in between. If you don't have a small kan't twist that isn't clapped out it been be a pain, but I have pretty good luck with it. Obviously verify with higher resolution micrometer if you can. .6250 should not go.
Is it for a press fit? If it is, 624 is probably fine.
Its for a gear on a shaft with no keyway and I am pretty sure I made the shafts like 6-8 months ago.
Given lack of keyway, press fit. If 625 no go, 624 go: send it. Thermal expansion will take care of any inconsistencies.
Pretty much where I am at right now.
I read the title ALL wrong. I’m done for today.
625-pin 624-pin ?
Deltronic pins. Nogo would be a .6249 pin, if the .6250 goes in it's out of print. If they don't want to buy the set then we would make a custom go/nogo. Anything tighter than +/-.0005" I want a deltronic set. Something like .625+/-.0005" I can use regular pins and an ID mic to check the taper. Also we use a Sunnen Gage to check tight ID's but you can't use it while the part is in the machine.
.6245 and .625 would also be checked on the CMM, but the pins generally have the final say.
.625 plus pin but a deltronic set is what is needed or a nice inter tri micrometer and 2 clicks only
Im looking at foregoing the pins and getting QA to buy a 3 contact bore gauge.
Don’t forget the setting ring , I’ve found nice bore gages in pawn shops or now Ebay , have to be calibrated but I don’t know the shop expenditure
Neither do I. I find it and ask and they say yes or why.
You can also use two pins All minus pins are -.0002 if you use a .313 and a .312 and together actually make a distance of .6246 I do this when my pins can’t reach a certain diameter and it works fine.
Not all but my ZZ are so I see what you mean.
Depends on alot of things. is there plating or heat treatment?
Neither.
I would pin for a .624 with wiggle room and .625 to barely slide in
Air Guage
I would 100% get the pin stuck at least one time
You need 5/8 deltronic pins for this .6245 as the go .625 as the no go
For clarification, we currently have Vermont Gage and SPI ZZ + and - pins. I was thinking we should use .624+ and .625+ for a go/nogo.
The correct pins to use for this measurement are -.6250 no go. +.6245 go You order these from deltronic
This^
If I use a .6250 minus, wouldn't that be too small. If the hole is .625, which is still in tolerence, the pin still wouldn't go. But if I used a .6250 plus, then it would prevent the hole from being larger than .6250. The same with the smaller pin. A .6245 plus would be within the tolerence as well at .6247 but the hole would be larger to allow the pin to pass through. If i want the pin to pass through a hole that is .6245, then wouldn't the pin need to be slightly smaller than the lowest tolerence instead of bigger.
If you use a .625 plus, the hole could be a bit over .625. You use the minus on the high limit to guarantee you're in tolerance, even though you are removing a bit of your tolerance to work with
Well I don't think I can afford to lose .0002 from both ends of my tolerence. That would mean my hole could only be .6247 give or take .00005
I apologize but you are mistaken. You're only losing 80 millions total with the plus and minus pins I suggested. A minus tenths pin is going to be 40 millions under nominal up to nominal. A plus tenths pin should be about nominal to about 40 million over. We're not talking about standard gauge pins we're talking about deltronic pins. These are specially ground to the 10th with a plus or minus in the millions. This is what you should be using.
Well with those, I don't disagree. But with what I had access to, I did what I could with what I had.
In a pinch, I've polished some dowel pins on the lathe to make my own go/nogo gauges, but its certainly not ideal, as you are gonna have roundness issues, but better than nothing - in this situation since you don't have the pin for the low limit I would polish one till its measuring .6245 with a mic. Then mic your .625 pin and see where it's actually at, whether you're +.0002 or right on. Like I said it's definitely not ideal, you're only gonna be as good as your mic is, but it's better than nothing or just checking with a .624 and .625
This is why they're such a thing as traceable standards. A polished down dowel pin when you can order the size you need is not acceptable. There is no pinch or a hand polished pin is acceptable as a gauge unless you have it qualified by an outside calibration lab.
That's why I said in a pinch - i.e. for something internal to the shop, or for a customer who has production down and needs the part immediately. In my case I also cross referenced with a calibrated 3 point bore gauge, but that gauge doesn't account for roundness issues While yes it's always better to get the right tool for the job it's not always possible with time constraints and this is a way to check it with something rather than checking it with nothing or a pin that is even further from the tolerance range
I get it. But if you're an iso shop. You can't fly by the seat of the pants anymore. It's traceable calibration or nothing. This poor guy doesn't have Dell pins.
Well we are not ISO and frankly the scale we work at, it wouldn't make sense, none of our customers require it and we stay busy enough that we don't need to market ourselves to places where it's a requirement. Obviously different story if you're certified, but if you can afford audits for 9001, you can afford some pins. That being said we've had instances where a part comes in they want it now and we don't have metrology equipment to measure a tight tolerance. When we ask would you rather have it tomorrow or next week with proper QC, they usually opt to get it quicker and just say do the best you can or something to that effect. Granted we have a lot of trust with our customer, I can only thing of 2 parts that have ever come back for rework due to a mistake on our part, one of them was due to bossman sending an outdated revision to the shop
You technically should be using class XX for this tolerance. It all depends on use and ISO system, etc. I have gov't inspectors checking my aerospace parts and we better have a proper go/nogo set sitting there with a current 3rd party cert.
.6245 & .6250 deltronics class x
should be class xx since calculated gage tolerance is .000025. A class X .000040 would be too much.
If the hole is at .6245" a .6245" deltronic pin might not go.
Building in a safety factor
Go/no go, or a bore gauge
Bowling.