The ability to measure

[jackieschmidt]

The question I would pose is that do you really need to measure to that fine of degree when you consider all the variables in reloading components, environmental conditions affecting shots on target and the limitation of the shooter's skill.

Maybe bench rest guys need to do this, I don't know since I never participated in that discipline nor ever had the interest or mental makeup for it.

As a Benchrest Shooter, about the only time I am concerned with measurements in tenths of a thousanth is when I am making my bullets. Being that accurate is a necessity in bullet making.

 

[hoz53]

I was reading a post on the forum the other day and was impressed with the posters ability to measure to .0001. I thought to myself Holy crap he must have some very accurate measuring tools. There was a picture included and the dial indicator was in the picture. I thought to myself I want one of those that goes to the 4th decimal point, and right now. So I blew up the picture as large as my computer would allow to get the model number, and to my surprise the manufacturer of the indicator had printed right on the face of the indicator that it was only capable of .001, or 3 decimal points of accuracy not 4 so how does this poster get the extra accuracy he is claiming? Is there some dial indicator guru like SParker with scales that fixes them, or something I don't understand? Please help I want the .0001 so I can make the best ammo I possibly can.

i think i can measure accurately to 0001 with some of my tools. Now all i need to do is beable to read those metric mics— har

 

[K22]

As a Benchrest Shooter, about the only time I am concerned with measurements in tenths of a thousanth is when I am making my bullets. Being that accurate is a necessity in bullet making.

Wow, you make bullets, I am impressed!

 

[ebb]

The guy on U tube says since the metric people didn't go to the moon, and we did stick with SAE.

 

[6BRA]

I believe there are several videos of Jack Neary talking about neckwall differential of .0002. In fact on this very forum within the last week tons of input on icing down your neck turner to achieve consistent neck walls. I'm sorry but there are several things in benchrest that require more than .001. I can measure 4 decimals all day long outside of a lab environment. Everyone has an opinion.

 

[Rocketvapor]

Lab environment?
Take 68F for a dimensional lab.
Measure a piece 3" long of Steel or brass with a Stainless Steel Micrometer (or Caliper) in a lab @ 68F.
Now, take everything into the kitchen.
At a comfortable room temperature of maybe 75F, the brass would have grown at 8 uin per degree per inch
8 X 3 X 7 or 168 uin (0.000168").
The measuring device would have grown (across the 3") at 6uin per degree per inch,
6 X 3 X 7 or 126 uin (0.000126")
A thermal error of 40 uin (0.000040").
What would the 75F error be for a 3" piece of SS?

For a mic that reads to 50 uin, warm gives you an extra count @3" for brass.
Correct for it.

Now take a 3 inch piece of brass, add in a 1 inch Aluminum case adapter, a caliper @ 4".
You have 3" of brass plus 1 inch of aluminum less the thermal expansion of the measuring instrument across 4". Do the math and correct for it.
At what temperature would the measurement of a 3" brass case (plus a 1 inch Hornady aluminum case length gauge) give you a WHOLE one tenth error?

 

[Alex Wheeler]

I can measure a tenth. By that I mean I can measure something multiple times and the mic will read the same to a tenth. Does that mean its its actual size, no. For that you need the controlled environment and highly calibrated tools. We only need comparative measurements. Like Jackie said theres things in bullet making we need to measure that small. All you need to know is if one punch is a tenth or two bigger than the next. Knowing the exact number doesnt matter. It does take experiance but its 100% doeable. Same with dialing a barrel. Yes you can do it better than a tenth with good tools. Again we are not measuring the bore. For dialing a barrel you could take all the numbers and hash marks off the indicator but one. This gets confused often, theres a difference between measuring a part for actual size and just getting a repeatable number.

 

[dgeesaman]

I can measure a tenth. By that I mean I can measure something multiple times and the mic will read the same to a tenth. Does that mean its its actual size, no. For that you need the controlled environment and highly calibrated tools. We only need comparative measurements.

Agreed, especially when we consider how much other more influential things are changing like our optimal powder charge or bullet seating depth.

I think it also bears mention that production environments can be very hard on measuring tools in a way that doesn’t happen for most reloaders. If a reloader can measure a 1.5-2” length with reliable consistency to within .001” using calipers, then they can do it. The fact that it doesn’t hold up in less ideal conditions does not invalidate it.

 

[Rocketvapor]

All of these measurements that don't matter because some other measurement is more important might have a little impact down range.
So, back to my cheap caliper evaluation.
Zeroed, and measured a 4" Jo Block @ about 71F.
Then chilled the block to about 53F.

Then chilled to about 42F.


Think I'll warm the block up next.

 

[Jonnyofalltrades]

I can measure 4 decimals all day long outside of a lab environment.

Maybe....
Do yourself a really big favor.
Measure several precision objects to the tenth.
Then get a few people who's machining/measuring skills you respect to measure the objects.
You WILL get different numbers.
Who's right?
Measuring pristine gage blocks is helpful for developing technique, but almost nothing in the real world is built like a gage block.

 

[Rocketvapor]

Agree.
Blocks and pins are good for technique and to evaluate instrument performance,
Add in user error and parts like measuring rifle case length or loaded rounds and the part adds another source of error.
Brass or Aluminum might need temperature compensation.
When the linear temperature coefficient of the part being measured is different than the measuring instrument best measurements will be best at a standard (lab) temperature.
Think about a round with case/bullet being measured with a SS device.
Machinists working out in the shop have correction data for shop temperature so the parts check out in the QC booth.

 

[hogpatrol]

I assume all that are using measuring instruments to a tenth are having them calibrated and certified.

 

[Rocketvapor]

Not difficult to do your own calibration.
Actual certification to NIST traceable standards is NOT required for personal, at home measurements.
Most Labs will give you a Compliance Statement.
Test data usually COSTS MORE.
The traceable certificate for the 4" block shows it's 8 micro inches short.
I did not correct for that in the above tests.
And the set is past it's 1 year recal date.
Those that have good mics that are 20 years old have been sent in to a LAB how many times?
Check out RE-Calibration costs. Maybe once a year?
And remember that NIST Traceable is DIFFERENT than Calibrated/Certified @ a government NIST facility.

 

[hogpatrol]

Back in the old days, I used a six foot caliper on large diameter workpieces, larger got the pi tape. The caliper and other measuring tools were kept in a temperature controlled room and calibrated and certified there for U.S. Navy work. When I worked in a shop at an aviation maintenance facility, any tool that had to do with measuring, was sent out, calibrated and certified on a regular basis.

 

[Rocketvapor]

I ran a NASA (Contractor) Calibration Lab. Some items needed to be sent out to a Primary Standards Lab, and a few had to be sent (or transported) to Gaithersburg or Denver.
In some cases basic S.I. definitions were used to calibrate some instruments using other measurement units or even ratio metric methods.

Pi Tapes , we calibrated 1040" Pi Tapes with a HP laser.

 

[Jonnyofalltrades]

Back in the old days, I used a six foot caliper on large diameter workpieces, larger got the pi tape. The caliper and other measuring tools were kept in a temperature controlled room and calibrated and certified there for U.S. Navy work. When I worked in a shop at an aviation maintenance facility, any tool that had to do with measuring, was sent out, calibrated and certified on a regular basis.

The biggest mic I ever saw was 6 meters.
I didn't personally use it, but the machinist overseeing it's use told me that the mic would be laid on the workpiece for at least an hour before taking a measurement, to allow their temps to be similar. There's a lot of skill involved there. 6 meters is about 20 feet. That was on steam turbine housings.

 

[Rocketvapor]

I'm pretty happy with the Cheapo replacement caliper.
Various pins, blocks, and some parts like bullets and I have NOT been able to get any errors close to 0.001"
Back to room temperature with the 4" block (no dial adjustment) is as close as these old eyes can see.

I cheated though. Lab temperature (Kitchen is above 68 degrees) and the block is short (8 uin).
Yes Dear, Time to move the temp in the house up a few degrees .

 

[Rocketvapor]

Here is a little measurement exercise. An Aluminum Ring.
Part and Caliper @ about 74F.
Measurements are UN-Compensated for temperature.
Values As Measured, interpolated/estimated dial readings.

OD correction is about 0.0002" for the ring, 0.0001" for the caliper (Caliper and Ring Correction, 74F to 68F is about 0.0001").
This is FUN
Previous Pin test when I received this caliber.

 

[AlNyhus]

With a quality non-digital micrometer and good technique....reliable, repeatable measurements to one tenth of a thousandths is pretty routine. I have one micrometer that's used only for my bullet making for consistency. Taking the time to clean the carbide faces correctly also helps consistency.

Good shootin' -Al

 

[hogpatrol]

With a quality non-digital micrometer and good technique....reliable, repeatable measurements to one tenth of a thousandths is pretty routine. I have one micrometer that's used only for my bullet making for consistency. Taking the time to clean the carbide faces correctly also helps consistency.

Good shootin' -Al

Those tiny little lines you have to match up can be a problem for someone's eyeballs. I remember testing an apprentice candidate with one. He had trouble with the 0-1 mikes but what flunked him was when I asked how many thousandths in one inch. His reply was "They're pretty small, must be a million of them".