Pin Gage Question

[Rex Walters]

You’re missing the point.

One of us is missing the point for sure.

Pin gage sets come in one thou increments whether you buy plus or minus tolerances. Either way, the difference between go and no go is roughly a thou.

Anything between go and no go requires feel, just as using a micrometer or a bore gauge requires feel and skill. Are you arguing otherwise? Can you not feel the difference between a pin in a 0.0001” oversized hole and a 0.0005” oversized hole? The absolute amount is subjective, but I’m afraid that feel is required for precision machining. No amount of GD&T will make it otherwise.

I’m honestly not sure what you are arguing about, but I’m firm in my conviction that
pins that are toleranced to be at or under their marked size are the ones you want for “real world” boring operations rather than QA inspection to absolute measurements.

 

[Rex Walters]

my gauge blocks which are accurately ground but the finish isn't good enough that they can be ringed...

That’s surprising from Accusize. Would they not take them back? Wringing definitely requires a lapped surface which is why gage blocks are so blasted expensive, but if they are really intended as Jo blocks rather than simple setup blocks (with to the tenth stackups) then wringing definitely seems mandatory.

 

[verbotenwhisky]

That’s surprising from Accusize. Would they not take them back? Wringing definitely requires a lapped surface which is why gage blocks are so blasted expensive, but if they are really intended as Jo blocks rather than simple setup blocks (with to the tenth stackups) then wringing definitely seems mandatory.

For the price and what I use them for I was good with them, they are at least accurate, I just assumed it is the finish...

 

[SouthernChap]

You might check Amazon and Accusize stuff when looking for this sort of thing, I have had good results from them. Ali/Alibaba is the Chinese Amazon and I do not mean they sell Chinese stuff, I mean they are China based so I tend to try to avoid them.

Unfortunately Accusize aren't available here in the UK. Given what I hear about them (and the fact that I have an sentimental fondness for Canada), I'd have an awful lot of stuff bought from Accusize by now, if they were.

Amazon UK didn't have much in that limited space between dubiously cheap and north of £500 for a single set when I was looking. It's better now I notice, but the sets I could justify, bear a striking resemblance to what I have, so probably from the same factories.

Consciously choosing not to buy from China is an admirable stance, I'll grant though.

I'd guess one very good reason to buy from a specialist vendor (and that means not China) though, is that you can choose whether you want a + set or a - set (which until I read this thread, I didn't know was a choice).

Looks like I ended up with + sets. At some point I guess I'm going to need to get a - set and from somewhere I can specifically choose a the direction of tolerance. Still early on in my journey as a hobby machinist but I'm guessing the 0.5 - 5mm set would probably be the one to get.

 

[stupoty]

Thanks for all the replies. It is much appreciated.
I bid on a Vermont .251 to .500 set on eBay. I should have put a higher bid in than $120. They sold for $122....hahaha.
That set goes $300 brand new.

I'll keep on the lookout and try to make my mind up. I have a few weeks away at work yet so there is time.

If you are making something and will need to gauge holes you can always make your own pins for each size you need , depends on how much use you will get from the set I guess.

Stu

 

[Liljoebrshooter]

You guys are giving me the feel of being on practical machinist site.
Arguing over tenths. This is the Hobby Machinist site.

Yes I own hundreds of gauge pins and use them very often. They are just another tool to have available to help with a job.
Joe

 

[SouthernChap]

Right I said I'd put the numbers up from my AliExpress sets. Here they are (late as usual, I'm crap at time estimating, just ask my boss!):

(n1 and n3 are either ends of a pin and n2 is the middle)

Specified Dia.	n1	n2	n3
0.500​	0.504​	0.504​	0.505​
1.150​	1.152​	1.153​	1.153​
1.800​	1.801​	1.802​	1.803​
2.450​	2.454​	2.454​	2.454​
3.100​	3.104​	3.104​	3.104​
3.750​	3.751​	3.751​	3.752​
4.400​	4.404​	4.402​	4.403​
4.950​	4.953​	4.953​	4.953​
5.000​	5.001​	5.001​	5.001​
5.300​	5.301​	5.303​	5.302​
5.950​	5.951​	5.957​	5.951​
6.600​	6.603​	6.603​	6.603​
7.250​	7.253​	7.252​	7.252​
7.900​	7.901​	7.903​	7.904​
8.550​	8.553​	8.552​	8.553​
9.200​	9.202​	9.203​	9.203​
9.850​	9.854​	9.853​	9.854​
10.000​	10.003​	10.003​	10.004​

I've highlighted the one big deviance; that might have been my measuring, though. I did have a 5 minute break after doing that particular pin as I think I was getting a bit bored (and thus maybe a bit sloppy!).

One thing I don't like is the little tubes for each pin in the sets. That's one extra bit of messing around before you have the pin in your mitts. Not sure if I can face making nearly 190 correctly sized wood pieces from square dowelling, and then drilling a hole in each to the nearest mm, though!

 

[Bone Head]

First, I'm anal about measurement Due to working with tight requirements I guess, or maybe I'm just an A-hole. Keep both in mind.
You are not actually "measuring" with gauge pins; just checking holes to see if they're within the dimensions specified. Check the tool with a good tenth mic to see the actual size of it.
Now an inspection tip. As the pin enters the bore slowly twist/rotate the pin. This is to catch the pin before it gets jammed in the bore. A good pin is made from pretty hard material which is hard to machine out. Hard enough to possibly damage that hole you're checking.
I'll keep my trap shut for the rest of this thread; pleas continue.

 

[Rex Walters]

the one big deviance

7um over nominal (about 0.0003”) in the worst case doesn’t seem that terrible. Clearly this is a plus set (all measured values were at or over nominal).

For the record, I generally machine to the closest thou (I have much less metric tooling). But working to the closest thou means I need gauges and standards that are held to tighter tolerances.

For the reason most concisely expressed in comment #42, I prefer minus toleranced pins for gauging a hole (“measuring” is common parlance but even micrometer measurements are relative to standards).

 

[projectnut]

All the discussion about accuracy to .0001" or tighter is interesting, but I'd like to know exactly what members are building that requires that level of accuracy. By "exactly" I mean I would like to see the actual project(s) requiring such accuracy. I understand it's nice to be able to work to those levels, but is it necessary, or are you just doing it because you can? I have so many projects either in progress or waiting in the wings that I'm rarely going to spend the time to get to that level unless it's actually needed.

I worked in a shop for over 20 years designing and building food processing and packaging machinery. 90+% of the parts only needed accuracy to .005". Tight tolerance parts would be to .001", and precision parts would be to .0005". I would guess less than 1% of the parts required an accuracy of .0001"

In the real-world time is money. I've mentioned several times in the past that we were often warned not to specify tolerances tighter than necessary. As the tolerance tightens the price increases. We were often told to remember that for each place the tolerance decimal point moves to the left the cost decimal point moves an equal number of places to the right.