All calipers not created equal

[DougGuy]

Try 2 Thousandths, .002, .499 to .501.

This alone should be a final argument for a DECENT 0"-1" micrometer. I use digital calipers when I am rummaging through my box of drill bits, this is about ALL THEY ARE GOOD FOR. Outside of this, might as well be playing pin the tail on the donkey.

[Ole Joe Clarke]

What they said, use a micrometer that is calibrated properly.

Have a blessed day,

Leon

[Dieselhorses]

It is not unlikely that the Lee sizer is not true producing an out of round bullet. After buying three Lee sizers, I quit them as the sizing chamber was bored on a tangent to the main axis and the other two were simply out of round. You need a standard to test your instruments against to know if they are accurate and in calibration.

Further, you are measuring a painted bullet. While I have no experience with coated bullets, I doubt the coating is perfectly uniform.

I can make a video if you'd like of me turning the bullet an 1/8" at a time. Wrong measurement or not, if it's the same all the way (full circumference) would it be safe to say it was round? And if it is a perfect round, I have no reason to believe that my sizer is "tangent".

[jmorris]

If I want a precise measurement I don’t use calipers, that’s what micrometers are for.

If you get some gauge blocks or standards you can learn proper techniques for getting very close with calipers though.

[country gent]

For the most accuracy in a measurement its jo blocks a granite plate and indicator with heavy stand. Jo blocks are stacked up to dimension indicator on stand zeroed and then used to part. This gets the closest most accurate measurement possible. The next is jo blocks stacked and wrung together and micrometer. wrung blocks are measured with mic and reading noted then the part if reading are the same then the part is right. then is the mic zeroed at some point other with a standard. Precision measuring is a skill that takes awhile to learn and develop. Its a proves that must repeat, be checkable and be the same from location to location. A part made in one plant must git the mating part in another plant. A bullet made in one shop has to fit the cases dies rifles everywhere.

[44magLeo]

I have tried battery powered measuring tools. I think if you spent enough on them, they may work. But at any price most can afford they are not trustworthy.
I have several dial calipers that I trust. One is even metric. I use these for case length's. I have a 1 inch mike for diameters.
Battery powered tools often need to warm up for at least a few minutes before they work right. They tend to drift from interference from other nearby electrical devices.
I have several electric scales. I bought them to weigh boolits. Thought they would be fasters. The most costly was around $35. You put the same boolit on the scale 5 times and get 5 different weights. Not by a few hundredths or tenths but by 3 to 5 grains.
They get used as paper weights.
Leo

[6bg6ga]

I've found cheap plastic calipers without a dial just as accurate as Starrett. Measure a jacketed bullet and you will be right on with anything you pick up and if not its you not the instrument.

[EDG]

Hold the caliper in your hand for 5 minutes and it will expand. Then the measurement will be wrong.
This is because the thermal coefficient of expansion is much higher than steel.

I've found cheap plastic calipers without a dial just as accurate as Starrett. Measure a jacketed bullet and you will be right on with anything you pick up and if not its you not the instrument.

[Bazoo]

I don't see listed, what brand is the digital caliper?

I don't see the draw to digital calipers. I guess if your blind and can't see the marks on a dial. But then, if you can't see that, how do you inspect cases?

[15meter]

I've got a Mitutoyo 0-6" digital caliper, I check it regularly against jo-blocks at several points along the range that I use, in 20 years it has always been spot on. The battery/warmup time is a non-issue with these, it is never off and the battery life is measured in 12+months between battery changes. I've got a Starrett 0-6" dial that has the same kind of accuracy/repeatability. I can't remember the last time I got out one of the Starrett or Lufkin micrometers because either of my calipers is accurate enough for what I measure. The Mitutoyo's stated accuracy is +/- .001 with a repeatability of .0005. I've run gage R&R's on it and mine actually tests better than that.

For a micrometer unless you get a tenth's reading mic with the vernier on the barrel, I'm not sure a standard micrometer will do any better and reading the vernier is something old guys eyes are not meant to do.

And I'm not blind, but it is definitely easier to read the digital display and less likely for me to transpose numbers in my head like I'm prone to do when using a dial.

For function and hand feel I like the Starrett dial better, I just think I'm a little less prone to a measurement error with the digital

[country gent]

Newer dials are shielded better but I had fine swarf and dust get in the rack ad affect measurements. Had one set that when this happened would occasionally jump a tooth or 2 and require being reset and recalibrated. When I first saw dials they were 0-100-0 dials 200 per revolution not th3 0-100 dials and 100 rev like todays.

[EDG]

With a micrometer you get a much more consistent feel when measuring different shapes.
In pinch you can even guess at the nearest .0001. If you have a Swiss made Tesa or Etalon the thimbles are marked with .0005 graduations. This makes it possible to use an easier to read vernier with just 5 lines. In addition if it is important some of the mike designs have a fat thimble that makes the tenths easier to read. Those include the very expensive Tesamaster and the Mitutoyo model 106-102 with non-rotating spindle.
A caliper might test ok on a standard but it will never give a good consistent feel on a wide variety of work pieces and it is never going to be consistently good to .0005 no matter what the display says. A mike can be trusted to better than .0005 and usually to .0002 even if you have to guess when there is no vernier.

I've got a Mitutoyo 0-6" digital caliper, I check it regularly against jo-blocks at several points along the range that I use, in 20 years it has always been spot on. The battery/warmup time is a non-issue with these, it is never off and the battery life is measured in 12+months between battery changes. I've got a Starrett 0-6" dial that has the same kind of accuracy/repeatability. I can't remember the last time I got out one of the Starrett or Lufkin micrometers because either of my calipers is accurate enough for what I measure. The Mitutoyo's stated accuracy is +/- .001 with a repeatability of .0005. I've run gage R&R's on it and mine actually tests better than that.

For a micrometer unless you get a tenth's reading mic with the vernier on the barrel, I'm not sure a standard micrometer will do any better and reading the vernier is something old guys eyes are not meant to do.

And I'm not blind, but it is definitely easier to read the digital display and less likely for me to transpose numbers in my head like I'm prone to do when using a dial.

For function and hand feel I like the Starrett dial better, I just think I'm a little less prone to a measurement error with the digital

[1hole]

I worked 15 years as a "precision measures equipment lab-electronic" (PMEL/E) repair/calibration technician in the space program. It is (or at least was) understood that any digital read-out was the factory accuracy percentage plus or minus one count. I didn't do digital physical standards (micrometers/calipers) but their accuracy plus/minus one count would still apply. IF you think you need accuracy better than one thou get a tool that measures to ten thou (0.0001") and expect to pay some big bucks for it!

Precision reloaders need a decent caliper and/or micrometer; a 6" caliper is most useful and plenty accurate for our real needs. I've not seen every caliper ever made but I've only found two grades of them.

The first are the excellent but costly professional machinist tools such as Starrett, Brown and Sharpe or Mitutoyo but even they need regular certified lab calibration to be dependable. They're great tools but it's hard to justify their cost for what reloaders do.

More reasonable are the low cost small shop/hobbyists tools (like those for us reloaders) made in China, some of which carry reloading brands from Midway to Lyman to RCBS. When the sliding is jaw squared as described above, I've seen NO consistent difference in any Chinese made brand, including those from Harbor Freight Tools, dial or digital, which are often on sale for as little as $10-$15. I've had some 7-8 H.F. 6" and one 12" calipers in my little home machine shop and loading room for some 15+ years; my two Jo blocks - in 0.030" and 1.0" - say they are all either dead on or, worst case, off no more than half a thou. (And, my three digitals have no rack gear to collect swarf!)

Meaning, except for bragging rights, the professional grade tools mean little or nothing to a reloader. Nor does price/brand of the Chinese tools. We can pay a little for H.F. or a lot more for RCBS but those I've seen look like they are all made in the same Chinese plant!

[1hole]

I worked 15 years as a "precision measurement equipment lab-electronic" (PMEL/E) repair/calibration technician in the space program. It is (or at least was) understood that any digital read-out was the factory accuracy percentage plus or minus one count. I didn't do digital physical standards (micrometers/calipers) but their accuracy plus/minus one count would still apply. IF you think you need accuracy better than one thou get a tool that measures to ten thou (0.0001") and expect to pay some big bucks for it!

Precision reloaders need a decent caliper and/or micrometer; a 6" caliper is most useful and plenty accurate for our real needs. I've not seen every caliper ever made but I've only found two grades of them.

The first are the excellent but costly professional machinist tools such as Starrett, Brown and Sharpe or Mitutoyo but even they need regular certified lab calibration to be dependable. They're great tools but it's hard to justify their cost for what reloaders do.

More reasonable are the low cost small shop/hobbyists tools (like those for us reloaders) made in China, some of which carry reloading brands from Midway to Lyman to RCBS. When the sliding is jaw squared as described above, I've seen NO consistent difference in any Chinese made brand, including those from Harbor Freight Tools, dial or digital, which are often on sale for as little as $10-$15. I've had some 7-8 H.F. 6" and one 12" calipers in my little home machine shop and loading room for some 15+ years; my two Jo blocks - in 0.030" and 1.0" - say they are all either dead on or, worst case, off no more than half a thou. (And, my three digitals have no rack gear to collect swarf!)

Meaning, except for bragging rights, the professional grade tools mean little or nothing to a reloader. Nor does price/brand of the Chinese tools. We can pay a little for H.F. or a lot more for RCBS but those I've seen look like they are all made in the same Chinese plant!

[Walks]

How no one is using a Micrometer ?

That what I was taught to use when measuring the diameter of a hopefully round bullet.

[Bazoo]

I bought the RCBS calipers over the other brands of china made because of RCBS' warranty. I figure if they break I'll get them replaced for only shipping. But I also figure, if they aren't all from the same plant, maybe they are a little better than some others, since RCBS will warranty them for life.

I had a HF set for a few years. I went to use them one day and noticed the needle flopping around on the shaft. They had a fairly easy life but did get dropped a few times on a wood floor.

[Dieselhorses]

Big thanks to everyone who shared experiences, suggested micrometers and professional advice. Also everyone who mentioned having a means for calibration as this makes a lot of sense! One perspective of casting is that we are sending a "not so perfect" projectile down a "closer to perfect" bore/rifling. Objective is to get the best fit. Also those who mentioned "getting the feel" of measuring diameters and such makes a lot of sense too. I just want consistency and if it means graduating to a micrometer then so be it.

[Drew P]

I worked 15 years as a "precision measures equipment lab-electronic" (PMEL/E) repair/calibration technician in the space program. It is (or at least was) understood that any digital read-out was the factory accuracy percentage plus or minus one count. I didn't do digital physical standards (micrometers/calipers) but their accuracy plus/minus one count would still apply. IF you think you need accuracy better than one thou get a tool that measures to ten thou (0.0001") and expect to pay some big bucks for it!

Precision reloaders need a decent caliper and/or micrometer; a 6" caliper is most useful and plenty accurate for our real needs. I've not seen every caliper ever made but I've only found two grades of them.

The first are the excellent but costly professional machinist tools such as Starrett, Brown and Sharpe or Mitutoyo but even they need regular certified lab calibration to be dependable. They're great tools but it's hard to justify their cost for what reloaders do.

More reasonable are the low cost small shop/hobbyists tools (like those for us reloaders) made in China, some of which carry reloading brands from Midway to Lyman to RCBS. When the sliding is jaw squared as described above, I've seen NO consistent difference in any Chinese made brand, including those from Harbor Freight Tools, dial or digital, which are often on sale for as little as $10-$15. I've had some 7-8 H.F. 6" and one 12" calipers in my little home machine shop and loading room for some 15+ years; my two Jo blocks - in 0.030" and 1.0" - say they are all either dead on or, worst case, off no more than half a thou. (And, my three digitals have no rack gear to collect swarf!)

Meaning, except for bragging rights, the professional grade tools mean little or nothing to a reloader. Nor does price/brand of the Chinese tools. We can pay a little for H.F. or a lot more for RCBS but those I've seen look like they are all made in the same Chinese plant!

Thank you for confirming this. I’ve suspected it all along, after purchasing over 50 pair HF dial and digitals and used many others along the way. They all come out of the same bins in China, hornady, rcbs, Fowler, HF, central, Lyman etc etc. I always thought starrett was the old middle quality brand, and mitutoyo is the beginning of the good kinds. I prefer B&S but I agree, for my purpose they aren’t really warranted as a dial caliper is only good for 1mil anyway. Heck, the last pair of tesa I bought was grittier than many of my favorite HF were. I loathe the electric ones, my Brian takes a lot more energy to read numbers than the needle. Especially in comparisons, probably the most common task for dial calipers.

[Drew P]

How no one is using a Micrometer ?

That what I was taught to use when measuring the diameter of a hopefully round bullet.

Because it’s much more awkward and time consuming, and limited range. Caliper can go 0”-12” and back to zero in 1 second.

[GregLaROCHE]

I have two digital calipers I bought from eBay. One seems to work better than the other. I am not crazy about either one. Even when I adjust the tension, the readings seem to change. I have a 1” micrometer that I use a lot. Especially when working with my mini lathe. I’ve been thinking about getting dial type calipers. How much do you have to spend for a decent pair?