Using Pin Gages

[ashlyngr]

Hello, I just bought a few pin gages (-), to measure my revolvers cylinder throats. Although I read quite a bit on the importance of knowing these dimensions, I'm a little unclear on how to use my pin gages.
I believe that a pin gage should smoothly pass through the cylinder from breech to muzzle end, or visa versa. To tight and not passing through, or to loose when passing through are both no-go measurements.
Do I have the correct understanding in the above?
Also, does someone know of an novice book on machining and tools?

Thank You,
Bruce

[country gent]

You will know when you get the right pin size as -.001 will "feel loose and +.001 wont go. When checking mark the cylinder your checking with a marker so you arnt getting diffrent throats every time. Check all 5 but do it one at a time. Pin gages are simple to use and its all feel with them. Dont force anything keep pin square and true lightly rotate as it enters. The right size will just feel a little drag as it slides in.

[uscra112]

What he said, but I like to have more than +.001 and -.001" Having the half sizes in +tolerance and -tolerance gives you a much better picture of what your throats actually are. I've been buying from www.gageshop.com, but they have a $25 minimum, so lately if I just need a couple I get them from www.use-enco.com.

[OuchHot!]

You can also buy individual pin gages from McMaster Carr quite cheaply. It might be good to look at the catalog as they have "go" and "no go" or the +/- gage available and I usually get each for just a couple of needed sizes.....this gets you into the 0.0002" range. I usually put a film of kroil or atf on them and am careful to not force anything. You might be surprised (appalled?) to find that many holes aren't round! I never bought a set as I just need sizes around 314, 358, 410 and 430. The sets in thousands are not as useful for my needs.

[Clark]

I have a set of .251 to .500 in the shop and one in the reloading room.

To these two sets I have started adding in between sizes for barrel spuds.
I have also got a larger set and a smaller set.

Buy them for the machine shop, keep them for the reloading room.

[W.R.Buchanan]

Just so everybody is on the same page here, pin gages are either Plus .0002 or Minus .0002 to the indicated size.

This is 2 Ten Thousandths of and inch, not .002 which is 2 thousandths on an inch.

There is very little use for "Plus" gages simply because in order to go in a hole that is dead on size, at say .250, you would have to use a .249 Pin which would be .0008 smaller than the hole. This would prove inaccurate.

As opposed to a "Minus" Pin which would be a .250 pin which would actually be .2498. The .0002 is all the clearance that is needed for the pin to enter a nominally sized hole.

Gage Pins are all about feel, but luckily it is not very hard to develop that feel.

Randy

[Larry Gibson]

+1 on W.R.Buchanan's post.

How many of you have a revolver that you can shoot accurately enough to tell the difference of a .0002" sizing in a cast bullet? The question was how many can do it, not how many think they can do it. I can't and couldn't even in my best day and I've never seen anyone that could. Never see a Ransom Rest that could either, just too many variable shot to shot.

I also have a large machinist pin set and have "pinned" a lot of bores and throats. If a .357 pin slips through the throat and a .358 won't and I'm using a .358 sized bullet then is there going to be any difference in the shooting?

Also remembering when pin measuring revolver throats that many have tapered throats and the slip through size only indicates the last/smallest diameter of the throat. If wanting a "perfect: fit in such throats I prefer to size as close to the largest diameter (rear of the throat). Otherwise, if the bullet is sized to the pin "slip fit" diameter, unwanted obturation and/or gas blow by may occur in the throat.

Actually though I seriously believe we carry this "perfect fit" a bit too far for most revolvers and the shooters ability of marksmanship. Does getting a "fit" down into the ten thousandths of an inch really make a difference in practical shooting accuracy from a revolver.....for any of us? Given the variables of alloy spring back, obturation in the case, variance in psi between shots, etc. ad nauseum is it really beneficial to measure such into the ten thousandth range and attempt to size cast bullets to that? Personally I've better and more productive things to do...........

Larry Gibson

[OuchHot!]

Rather than buying a set of pin gages in sizes that I would never use, I chose to buy a couple of +/- pins hovering about the expected/desired size. Say, for example; .358 +/- or .314+/-. This gets me to, for example .3138" and .3142" range of what I expect to see and lets me know if I have an egg shaped throat which can be easily corrected with a precision reamer. I have found that useful. I have found egg shaped throats to cause leading. An egg shaped throat can easily hold up a smaller than real pin. This has been worthwhile to me and cheaper than 26 pins from .25 to .5" made of Chinese who knows what. ymmv Just my way of being stupid, I guess.

[M-Tecs]

Both Larry's and W.R.Buchanan's posts are spot on. The bolded quote of Larry's is what you are looking to achieve.


+
Also remembering when pin measuring revolver throats that many have tapered throats and the slip through size only indicates the last/smallest diameter of the throat. If wanting a "perfect: fit in such throats I prefer to size as close to the largest diameter (rear of the throat). Otherwise, if the bullet is sized to the pin "slip fit" diameter, unwanted obturation and/or gas blow by may occur in the throat.
Actually though I seriously believe we carry this "perfect fit" a bit too far for most revolvers and the shooters ability of marksmanship. Does getting a "fit" down into the ten thousandths of an inch really make a difference in practical shooting accuracy from a revolver.....for any of us? Given the variables of alloy spring back, obturation in the case, variance in psi between shots, etc. ad nauseum is it really beneficial to measure such into the ten thousandth range and attempt to size cast bullets to that? Personally I've better and more productive things to do...........

Larry Gibson


Some of the cheap Chinese pin gage sets are highly suspect for accuracy and I don’t really care for the “loose” tolerances of pin gages. I much prefer Deltronic Plug Gages. http://www.deltronic.com/literature/plug-gage-pin-gage-guide.html. Way over kill for reloading but the toolmaker side of me won’t settle for anything less.

[W.R.Buchanan]

M-Tec: since you mentioned Deltoninc gage pins, it should be noted that they are available in .0001 increments if you really need to get technical. I have a few and they are nicely oiled up, as they don't get used a whole lot.

Randy

[DougGuy]

Mr. Buchanan hit the nail on the head, as far as correct math and application goes. There are a few good things to gain from using pin gages, and a few things to watch for. Since the .44 and .45 caliber Rugers are the most often brought up mfgr/make in these cylinder throat discussions, I would add that the larger the caliber, the thinner the cylinder wall/web etc, and the more chance for elliptical and oval, and just plain out of rounds misshapen chamber throats. With a -.0002" gage, or even a gage that's a half size under, you have the ability to "wiggle" the gage and watch to see if it moves more in one direction than another, meaning the throat isn't round.

Plus, Ruger has changed how they ream cylinders over the years, they used to gang ream them 3 at a time and maybe even 6 at a time, and as the reamers wore, the holes got pretty uneven. I think they are doing them differently now, and it seems like the newer .45s on the medium frame are more uniform around .4515" diameter.

I started to invest in some pin gages, and then I re thought that idea, and started using the boolits that I will shoot in the gun, to size with. I pick several known sized/good looking boolits out, clean the lube off, and "feel" the holes with it, and see if they feel consistent. Since we are sizing with the purpose of shooting a given diameter boolit, why not use the boolit for a pin gage? In all actuality, it's not really that important what number you can write on paper after pinning a hole, it's important that the boolit have a certain amount of light drag fit in the hole, and that the holes themselves, are consistent.

If you think about it, both ways work. Both schools of thought and measurement arrive at the same exact point. That is, the fitment of the boolit as it passes through the cylinder throat.

[M-Tecs]

One common misunderstanding of class ZZ pin gages is that they are .0002 over or under. They have a .0002 tolerance. For an over it is plus the tolerance, minus 0.0000 and for under it is minus the tolerance, plus 0.0000. If you have a plus pin at minimum tolerance and a minus pin at maximum tolerance they will both be the same size.

http://www.newmantools.com/meyer/pluggage_ABC.htm

http://www.aajansson.com/pdfs/understanding%20fixed%20limit%20gages.pdf

For the average reloaded none of this matters. For the guys swaging jacketed match rifle bullets it may matter.

For my applications I skip the normal ZZ grade sets and I only get the sizes I need in XX or X grade. This the XX or X grade you can use them as mike standards. With ZZ gages for some of my applications the .0002 tolerance is not acceptable.

[ashlyngr]

Getting back to this thread, I've learned much more than I hoped to learn. Thanks everyone. However, my efforts in learning to use pin gages, is actually my effort to choose the proper bullet size in building a viable cartridge. It is always preferable to size the bullet so excessive leading and good accuracy is attained "per an individual firearm". It has just occured to me, that all this effort will pass through a Lyman 4500 sizer die that is sized to their .000 dimensions. I haven't got that far yet, I hoping that in the final result everything comes together.

Thanks,
Bruce

[screamingjohnny]

I did not see an answer to your question about machining books.I would recommend the South Bend Lathe book, that Brownells carries. It will get you started in lerning some lathe skills.

[hodgeswalt]

Too many choices for me to recommend. Please take a look at the offerings from Little Machine Shop.com.

http://littlemachineshop.com/products/product_category.php?category=993665105

The above link will take you to a large selection of books that will get you started on becoming more proficient as a machinist.

Good reading,

--walt

[KCSO]

Actually for revolver throats i mch prefer ball gages. A good set aren't that much more expensive and they will work from 22 to 50 cal.

[M-Tecs]

Are you referring to these http://www.precisionballs.com/all_ball_gages.php or small hole gages http://www.starrett.com/metrology/product-detail/Precision-Measuring-Tools/Precision-Hand-Tools/Hole-Gages/Small-Hole-Gages/S829EZ ?

[Moonman]

If KCSO is referring to Small Hole Gages, they require a FEEL to set
and than READ a Micrometer to measure the gage.

Many not used to using these small precision tools would be
better served purchasing the Pin Gages (.0002 MINUS Set)

[dragon813gt]

Specs please? That looks like it will have zero recoil and will be great for kids to learn to shoot with :)

[KCSO]

Small Hole Gauges is the proper terminology. Sorry!

[Clark]

107745

Pin gauges in the machine shop.
Pin gauges in the reloading room.
Pin gauges at my desk.

I have lots of reloading dies, and I like to know the neck diameter.

[W.R.Buchanan]

Here's a hot tip for you guys using some kind of expanding hole gage and a micrometer.

You absolutely MUST measure any given hole several times to make sure you are getting a repeating measurement. All that just doing it once proves, is that the hole is some size. If you measure the same hole 5 times and get five different measurements it simply proves that you have no real idea what the hole's size actually is.

If you measure the hole 3 times and get the same exact reading 3 times then you are probably good to go.

You must get repeatable readings,,, period.

There is no substitute for being able to take accurate readings with your measuring tools. In a machine shop it is the difference in taking cuts that result in saleable parts and cuts that make the part into trash because it is now too small. You only stay employed for a short period of time if you can't make good parts.

Gunsmithing and gun work are all about Machine Shop.

All basic Machine tools IE: Lathes and Milling Machines, were originally designed and built for one specific purpose,,,

To make interchangeable parts for guns.

All other uses like Cars and Trucks and Airplanes, and any other thing you can think of are all "by Products" of guns.

Another way to look at it is the fact that if we didn't have the guns, we probably wouldn't have the cars or trucks or airplanes either.

Obviously accurate measuring tools have increased our ability to better use Lathes and Milling Machines. But just as you have to learn how to use a Lathe or Mill, you can't do it without learning to use the measuring tools simultaneously. They kind of go hand in hand.

Point being ,,, when you start out all your stuff looks bad and probably won't sell and you'll get yelled at. But as you put in the time, you get better and better until you can actually make a living doing this.

Then you spend all your money on guns.
So you see how guns have affected our history.... Almost as much as Beer! :drinks:

Randy

[DougGuy]

A split ball gage is pretty good for showing an egg shaped cylinder, and IF you can measure it close enough, you could measure the egg length, which is something you can only eyeball with a pin gage in the hole, as you will see light on the sides where the ellipse is. I see egg shaped throats on every one of the older Ruger cylinders that come to my shop for reaming. the medium frame cylinders have a much smoother finish, and much more round throats. Even though they are still undersized, they are beautiful.. Ironic it is.