Need help with micrometer use

[Patrick L]

Please bear with me; I'm no machinist. I'm fairly handy but its all self taught.

For may years I have relied on my Craftsman 1" micrometer. It has been a good solid tool, but it is only graduated to .001" An imbecile could figure out how to read it, and I did:smile:.

I just saw Enco had import micrometers that read to .0001 for $13.99. OK not aerospace quality but it seems fine for my uses. Now I need a little help with its proper use, as it came with no instructions.

I think I have figured out how to read it. There are 25 graduations per rotation, so 1 turn would be .025, 2 turns is .050, etc. Obviously you still read the spindle to the nearest mark to get the 3rd decimal, right? IE 2 turns plus 12 is .062, right? Then there are a series of 9 or 10 hash marks on the spindle, and one set of these will line up perfectly. I assume the one that does line up gives you the 4th decimal place. Is this all correct?

There is a little "wrench" packed with it. It seems to have end points that are used in the holes in the spindles. What is this used for? And on the face of the tool, between the spindle and where the cylinder goes into the measuring opening, there is a little wing lever. What is this for? And finally, do you need to "zero" these? When the ratchet on the spindle slips, it still doesn't read to 0. It is probably .0002 - .0003 out. On my craftsman .001 mic, it slips at zero unless there is a fuzzy or something on the face of the measuring surface.

Any help would be appreciated.

[largom]

Without seeing your mike with the "hash" marks I cannot comment on reading it. The little wrench is to adjust the spindle, which should be done with a "standard", a gage that is precise in size. If you really want to read in tenth's you should set the spindle with a gage. If there is a machine shop local you could probably get them to set the mike for you.

The little "wing" you mentioned is to lock the spindle. Usually a 1/4 turn locks it up. Take a reading on something and before moving the mike lock the spindle. You can now remove the mike and read it without the chance of the spindle moving.

Hope this helps. Larry

[hunterldh]

I think I have figured out how to read it. There are 25 graduations per rotation, so 1 turn would be .025, 2 turns is .050, etc. Obviously you still read the spindle to the nearest mark to get the 3rd decimal, right? IE 2 turns plus 12 is .062, right? Then there are a series of 9 or 10 hash marks on the spindle, and one set of these will line up perfectly. I assume the one that does line up gives you the 4th decimal place. Is this all correct?

You are correct. I now have a digital model but the 4th digit is still determined the same way.

[Bob Krack]

The wrench is to adjust the "zero".

I used micrometers from 0-1 inch to 23-24 inches working on steam turbines (my trade).

We were required to use Starrett brand although Browne and Sharp were allowed most of the time. I have no qualms about using the jap junk at home, but then again - plus or minus .001 usually makes very little difference in most uses. I still have my Starretts should the need arise.

I zero at "0" with a 0-1 and must use precision standards for anything larger.

Bob

[StarMetal]

You figured it out correctly. I can tell you this, with mine I will clean the anvil faces before I use it. This is especially true when miking lubed bullets because the lube sticks the anvil and when you run it down to zero it won't be zero due to the lube. So clean the anvils and they run it down to see if it is zero. I haven't had to rezero my mic with the wrench for years. It shouldn't need to have that done unless you might have dropped it or you turned the spindle way too tight instead of using the ratchet. I don't use the ratchet on mine.

Joe

[AZ-Stew]

Joe has a good point. Mine won't zero even with fingerprint oil on the measuring faces. When it's clean, it'll zero right out.

You're correct about the 4th decimal place.

When storing your mic, set it for about .010 and lock the spindle. Never store it closed (0.0000). This removes all strain from the tool.

Regards,

Stew

[Patrick L]

Thanks for all the replies. It appears I'm not as dumb as I've been accused of being.

Can someone explain how the wrenches are used to zero the mic? I did clean the faces and it still reads about .0003" when the ratchet slips.

[SierraWhiskeyMC]

I don't use the ratchet feature; I believe that puts too much strain on the micrometer. It will also tend to crush delicate objects when trying to measure them. It's not a C-clamp.

It takes some practice to develop a good light "feel" for it. Being consistent is very important.

Before I adjust the zero of the mic, I gently close it on a clean sheet of typing paper and pull the paper out. I repeat that process again. Then I close it against the anvil as if I were measuring something. If it doesn't measure exactly zero, I'll use the wrench to turn the barrel one way or the other until it's exactly lined up. Then open it a turn, and re-check.

Oh, never open or close the mic by using inertia to "flip" the "C" portion around; that causes excessive wear on the screw and thread. I hold the frame with one hand, and screw/unscrew the handle with the other. It takes longer, but a micrometer is a precision instrument that must be handled carefully to ensure accurate measurements and long service life.

[longranger]

Wow did I get some useful info from you machinist guys.
Great nuggets for those of us who only use a micrometer for gun stuff.:holysheep

[JIMinPHX]

Thanks for all the replies. It appears I'm not as dumb as I've been accused of being.

Can someone explain how the wrenches are used to zero the mic? I did clean the faces and it still reads about .0003" when the ratchet slips.

It depends. They vary a little from one brand to another. If you could post a few pictures, then maybe a few of the regulars here could help you out. Or, maybe you will just get lucky & someone else will happen to have the exact same one. It's hard to rely on that with the Chinese ones though. Even within a given brand name, they sometimes have multiple manufacturers & supply slightly varying examples of the supposedly "same" tool. Over in China, a single supplier often relies on a network of many small shops that make product for them.

In the mean time, until you figure out how to make the adjustment, you can just correct your indicated readings by subtracting .0003 from them.

[Echo]

The hash marks on the spindle are part of the vernier that supposedly gives you 4-place accuracy. The hash marks are spread out somewhat, so that ten of them spread over 11 graduations on the rotator. The two that line up give you the 4th place, just as you said.
And +1 for not swinging the frame around to loosen or tighten. And +1 for not using the ratchet - practice and get a smooth, uniform hand to tighten the Mikes uniformly from one trial to another.
It is my humble opinion that we realy don't need 4-place accuracy in our work...

[fourarmed]

Echo, I think if you look closely at the vernier scale on your mike, you will find that the 10 divisions of the vernier take up the same space as 9 of the main scale divisions.

We bought some new vernier calipers for our instructional labs this year. I wanted them just like the old ones we had. They divided each millimeter on the metric main scale into 20 parts. The business office had extra money to spend, however, and without asking me, they ordered some that were more expensive. They divided each millimeter into 50 parts. Our first experiment involved everyone in the class using a different caliper and measuring the diameter of a very uniform 1" rod. Guess what? The ones that measured to 0.002cm had no better precision than the ones that measured to 0.005cm. They were just harder to read.

Just because it reads to a tenth, doesn't mean it is reliable to that precision.

[Naphtali]

This doesn't address your query squarely. But it is, perhaps, important. While your 0-1" mic may be graduated in tenths, the best metrology you can expect is half thousandths. The only person I've known capable of close to tenths' accuracy with a Brown & Sharpe 0-1" mic was tool-&-die maker Bill Northcut, who worked in General Dynamics die shop in the 1970s. Since he could eyeball dimensions within a couple of thousandths, don't ask your mic or yourself to be capable of his freakish precision.

Just some thoughts.

[JIMinPHX]

we realy don't need 4-place accuracy in our work...

As a very old aviator once said - What's this WE business Lindburgh?

I don't know about you, but a lot of what I do needs to be good down to about .0002".

[JIMinPHX]

While your 0-1" mic may be graduated in tenths, the best metrology you can expect is half thousandths.

I can do 8 or 9 out of 10 test repeat measurements down to .0001" all day every day, anytime you would care to argue that point. I can even get .0002" on the cheap Chinese tools if I tune them up myself.

When I'm working down at that level, I check the tools against test standards that are at or near my measurement size right before taking a measurement. I can do that on an ID, an OD, a PD or any other reasonable surface that you might want me to measure.

There are guys out there in precision grinding shops that routinely measure down to 50 millionths or even 20 millionths. I can't do that very well myself, but I know more than a few that can.

While it's true that precision does not guarantee accuracy, you might be surprised at just how accurate a micrometer can be in the hands of a practiced individual. I can usually estimate accurately to .0003" or better on a mic that doesn't even have a tenth scale. I can do better than half a thou on a good pair of calipers or even a snap dial.

[Echo]

Fourarmed, I'm sure you are right. I didn't check my old B&S 0-1, and I remember way back being told that a vernier could be made either way, so I winged it.
And my son worked on improving a planarizing machine that smoothed semiconductor slabs to make IC's. Tolerance measured in angstroms.

I was working as a quality consultant for a local factory, and had several machinists, including the two shift foremen (both named Mike!), measuring parts. The average for one of the foremen was two tenths smaller than the other (both old time machinists), and he owned up to knowing he had a heavy hand. And what were the ACTUAL measurements? Who knows. One thing I learned at UAz was that measuring something introduces error - whatever it is, it is. When we measure it, that is when error is introduced. Training and practice reduce the error, but it will never go away. And I agree that most of our mikes should only be trusted to 1/2 thou. At least, that is what my Daddy taught me...

[Geraldo]

I was working as a quality consultant for a local factory, and had several machinists, including the two shift foremen (both named Mike!), measuring parts. The average for one of the foremen was two tenths smaller than the other (both old time machinists), and he owned up to knowing he had a heavy hand. And what were the ACTUAL measurements? Who knows. One thing I learned at UAz was that measuring something introduces error - whatever it is, it is. When we measure it, that is when error is introduced. Training and practice reduce the error, but it will never go away. And I agree that most of our mikes should only be trusted to 1/2 thou. At least, that is what my Daddy taught me...

Our dads thought alike. Interesting that you bring up a heavy hand on the mic. When my dad taught me how to use them I recall that he was big on consistency and not using a heavy hand when measuring.

For the guys who are measuring in tenths, I'm curious as to what are you working on that requires that level of precision?

[fourarmed]

Vernier scales are interesting. You can construct them about any way you want as long as you remember that n divisions of the vernier scale must take up the same space as n-1 divisions of the main scale (although 2n-1 works too, and gives a longer vernier scale). Rifle sight verniers usually have 5 divisions, 10 is the most common, I have calipers with 20 and 50 in metric, 25 in inch, and spectrometers that divide each half degree of the main scale into 30 minutes.

[monadnock#5]

Mic's do occasionally get used for taking dead nuts measurements. In which case, the amount of knowledge and experience possessed by the operator equates to the most accurate reading possible. No question. But then, how often do we need that kind of accuracy?

For most of the uses for which I use a mic, ultimate accuracy is a waste of time and effort. At work, we are expected to stay within a tolerance. The tolerance not only encompasses machine capabilities, but also the measuring abilities of the operators and their tools. At home, more often than not, I'm not taking a true measurement, only comparing one thing to another. Example: I mic the slug from my .30/30 barrel and it's .308. I then mic a boolit from mould #1 and it's .307, while a boolit from mould #2 measures .309.

By my measurements, I know that the only boolits that I have on hand to experiment with come from mould #2, and the boolits from mould #1 go into the recycle bin. My mic has served me well, and life is good. Whatever the "real" measurements of slug and boolits is immaterial. I've separated the wheat from the chaff, and am ready to move on.

[alamogunr]

While it's true that precision does not guarantee accuracy, you might be surprised at just how accurate a micrometer can be in the hands of a practiced individual. I can usually estimate accurately to .0003" or better on a mic that doesn't even have a tenth scale. I can do better than half a thou on a good pair of calipers or even a snap dial.

This statement can apply to many things. When I was in college(before electronic calculators) most students could get 4 significant digit results on a slide rule. Granted it was an educated guess, but we still felt justified in writing it down. The same applies to a man who is very familiar with his rifle or handgun and its ammunition. He will score more hits than I will with my multitude of guns even if we are both equally skilled. I prefer my B&S mic to the digital types. Especially since it cost me nothing. Nobody wanted to use the "old fashioned" mics, so they were surplussed.

John
W.TN

[cajun shooter]

I remember making more than one inside caliper in machinist school before I had the dimensions correct for the instructor. His reading of the mike was much better than my lightest file stroke. Da--n have to make another one, I thought that I would never pass year one.

[JIMinPHX]

For the guys who are measuring in tenths, I'm curious as to what are you working on that requires that level of precision?

Bearing bores, jack shaft diameters, press fit parts, shaft to gear fits, keyways, pitch diameters on gears, Thompson shaft, air bars, capillary tubes, gold leaf, inspection blocks, tooling & jigs are just a few of the things that come to my mind quickly. Guys that work in precision grinding shops probably measure just about everything down to tenths or better.

[Echo]

Yes, but Jim, Where do we need it in our reloading/casting addiction? As I implied before, any measurement we make is an estimate of the actual dimension. Our equipment, training, and expertise reduce the error in that measurement, but an estimate nonetheless.

[JIMinPHX]

Yes, but Jim, Where do we need it in our reloading/casting addiction? As I implied before, any measurement we make is an estimate of the actual dimension. Our equipment, training, and expertise reduce the error in that measurement, but an estimate nonetheless.

Boring sizing dies, resizing primer pockets, cutting mold cavities...