Show Me Your Micrometers

[Three44s]

Show me your micrometers.

I read about lands/groove dimensions from milsurps ..........

How do you do this ...........?

With a standard spindle mic, you can measure even numbered groove dimensions but what about the lands?

I have a ball mic but it still seems to bridge over to the grooves when attempting to read the lands.

Foolishly, this evening I mistakenly picked on a slug from a Smith & Wesson and realized my folly (five grooves) ............

........... How do you do odd numbered grooves?

Three 44s

[geargnasher]

I've never measured land or bore diameter, never felt it mattered with cast. It's groove diameter that matters to boolit fit and the engraving depth is whatever it is.

Several methods for the 5 groove, mine is not the best. Others will post.

Gear

[Gerry N.]

And this is why every one needs a copy of "Machinery's Handbook," so they can learn how to measure uneven numbers of grooves on a cylinder.

Gerry N.

[S.R.Custom]

I've never measured land or bore diameter, never felt it mattered with cast. It's groove diameter that matters to boolit fit and the engraving depth is whatever it is...

Indeed... For odd numbered grooves, I just rotate the slug in the jaws of a good caliper. In the case of the S&W, the opposing corners of the grooves are almost directly across from each other, and so this technique will indicate a diameter only a few tenths shy of the true diameter. Good enough for cast bullet work.

[rob45]

Like Gear said, the groove diameter is the one most important. But if you're really needing to find bore diameter by reading the slug, a blade micrometer is what I would use. Some people also use a small hole gage to measure the bore.

Some of the guys really serious in muzzleloading like to know both dimensions because taller lands (deeper grooves) are favored for patched round ball, while shorter lands are more applicable to slugs. So I guess there are some instances where one really needs to know, but those instances would seem to be rare.

Concerning the method of measuring the odd-numbered grooves, a very simple but definitely imprecise method is to wrap feeler stock around the slug, measure the diameter, and then subtract twice the stock thickness from your measurement to obtain the groove diameter. So if you're using .002" feeler stock and the wrapped measurement is .435", then after subtracting for the thickness of the stock (.002" x 2 = .004") your slug theoretically measures .431". Like I mentioned, this method is not as precise as you may want it to be. The "proper" way to measure uneven grooves is to use a specialized v-block.

There is a thread going on in the group buy discussion concerning such an item; you may want to check it out.
http://castboolits.gunloads.com/showthread.php?t=63965

Hope this helps.

[Bret4207]

Why not do it the easy way? Take a case fired with a full power load. Measure the inside of the case mouth. That's about as large as you can fire in that gun without neck turning. Start there and see if that isn't about the right size for good shooting. If things aren't working so good you can always go a little smaller and try that, but chances are about 80% plus of the time you'll have the size you need.

[243winxb]

For odd numbered grooves, I just rotate the slug in a Mitutoyo micrometer. In the case of the S&W, the opposing corners of the grooves are almost directly across from each other, and so this technique will indicate a diameter only .0001" or so, shy of the true diameter. Good enough for cast bullet work. For checking the throats of revolver cylinder, cast bullets, sized and unsized can give you a good idea on diameters. The gap between the barrel & cylinder can be measured with a feeler gauge. A gap of .004" to .009" is OK. A plastic gauge can work fine if measurement are repeatable. Its all in the ability of the person using the tools. IMO. http://i338.photobucket.com/albums/n420/joe1944usa/th_IMG_3873A.jpg (http://i338.photobucket.com/albums/n420/joe1944usa/IMG_3873A.jpg)

[dragonrider]

You could get a "V-ANGLE" micrometer but at $400 to $600 it ain't worth it. Best to use a v-block and indicator that can be had for less that $100.00 probably much less.

[Hip's Ax]

You can do it with a slug a mic and pin gages and some arithmetic, read about this on the internet. Not being 100% confident about the number I got with the previous method I sprung for a v anvil mic off of EPay (Chinese and not too crazy a price) and got the exact same number I got with the pin gages.

I used this on 3 groove 1889 Schmidt Rubin.

[odoh]

In 2nd yr HS Metal Shop Class, we made V Blocks from babbit ~ some 49yrs ago

[Catshooter]

Ok.

http://i379.photobucket.com/albums/oo235/Catshooter45/Micrometers.jpg

There's 11 there.


Cat

[geargnasher]

Ok.

http://i379.photobucket.com/albums/oo235/Catshooter45/Micrometers.jpg

There's 11 there.


Cat

:bigsmyl2::bigsmyl2:

I was gonna do that, but I counted eighteen in my mic drawer today at work and didn't feel like dragging them all home for a pic and a chuckle, figured someone else would have the same idea and I was right!

(plus, many of mine are Fowlers and I didn't want the flack from the machinists
here!:kidding:

Gear

[Three44s]

Now ....... now ........ we have gun porn, bullet porn ................

........... reloading bench porn ..............

..................... target porn ............... gun safe porn ...........

But when was the last time we had ..............

.............. micrometer porn????


Three 44s

[machinisttx]

Who needs a mic when you have a $600 set of Starrett Master series vernier calipers? :D

http://i16.photobucket.com/albums/b20/imakechips/100_0706.jpg

But I do have some pics of the bigger mics I've bought, well, one of them anyway.

http://i16.photobucket.com/albums/b20/imakechips/100_0693.jpg

I've got close to three full sets of 0-6" starrett mics, then a few others.

[Ohio Rusty]

Micrometer, caliper and barrel diameter gauges .... I'd be lost without my 'gun tools"
Ohio Rusty ><>
http://img.photobucket.com/albums/v372/OhioRusty/Tools-1.jpg

[AZ-Stew]

"Pin" or "plug" gages will accurately measure the bore of your firearm, just as in measuring a revolver cylinder throat. No need for a slug or fancy micrometer. On the other hand, groove diameter measurements require a good slug or Cerosafe casting. Methods for odd-numbered groove rifling are listed above.

Regards,

Stew

[Catshooter]

Well AZ, remember that when using a pin gauge you'll can have trouble if the item is out of round. The pin gauge will then lie to you, and badly.

Pin gauges work, but really they are the lazy man's way of measurement. :)


Cat

[10-x]

Anybody ever use a "Cadillac Gauge" height gauge? Use with a "Best Test" or similar dial indicator. IIRC one can meause just about any diameter using "V" blocks.....need a good calcualtor..........and a clean , flat surface........man that was years ago...............

[machinisttx]

Anybody ever use a "Cadillac Gauge" height gauge? Use with a "Best Test" or similar dial indicator. IIRC one can meause just about any diameter using "V" blocks.....need a good calcualtor..........and a clean , flat surface........man that was years ago...............

Yes, I used a genuine Cadillac Gage and not one of the japanese or other brand imposters. Excellent tool, but only as good as the indicator you use it with.

[10-x]

Yes, I used a genuine Cadillac Gage and not one of the japanese or other brand imposters. Excellent tool, but only as good as the indicator you use it with.

IIRC indicators were Starrett.......we even had Browne and Sharpe precision tools, still have my 1" travel B&S dial indicator:D. Used the Cadillac to measure pin/main diameters on crankshafts.....then came the air table precision measuring machine.........think B&S made part of it?..........way to many years ago.

[Bret4207]

Who needs a mic when you have a $600 set of Starrett Master series vernier calipers? :D

http://i16.photobucket.com/albums/b20/imakechips/100_0706.jpg

But I do have some pics of the bigger mics I've bought, well, one of them anyway.

http://i16.photobucket.com/albums/b20/imakechips/100_0693.jpg

I've got close to three full sets of 0-6" starrett mics, then a few others.

My verniers still work great, providing I can find my glasses to read them!!![smilie=b:

[AZ-Stew]

Until I found a $10 digital caliper, I used to keep a vernier set around my office. Even if I walked off and left it on my desk in plain sight, I knew it would be there when I returned. Hardly anyone these days can read one. No sense stealing it if you can't use it. Digitals and dial calipers are fair game for the light fingered, but I won't get too broken up if my $10 set walks off.

Regards,

Stew

[Char-Gar]

NO pics, but here is what I use.

1. 1" micrometer reads .001
2. 1" micrometer, with ratchet, reads .0001
3. 1" micrometer with friction thimble, reads .0001
4. 1" micrometers (digital) reads .001
5. 1" tubing micrometer, reads 001
6. 6" digital calipers

All of the above are Starrett.

There is also an assortment of scales, spring calipers, dividers, dial indicators etc. etc.

Like others I use a standard micrometer to measure slugs with odd number grooves. I rotate the slug between the jaws until I find the opposing high spots. Takes a little technique and feel, but it works just fine.

[badgeredd]

For odd numbered grooves, I just rotate the slug in a Mitutoyo micrometer. In the case of the S&W, the opposing corners of the grooves are almost directly across from each other, and so this technique will indicate a diameter only .0001" or so, shy of the true diameter. Good enough for cast bullet work. For checking the throats of revolver cylinder, cast bullets, sized and unsized can give you a good idea on diameters. The gap between the barrel & cylinder can be measured with a feeler gauge. A gap of .004" to .009" is OK. A plastic gauge can work fine if measurement are repeatable. Its all in the ability of the person using the tools. IMO. http://i338.photobucket.com/albums/n420/joe1944usa/th_IMG_3873A.jpg (http://i338.photobucket.com/albums/n420/joe1944usa/IMG_3873A.jpg)

SOOOOOOO very true! If one sizes a thousanth over his largest dimension, boolit fit should be correct.

Edd