Digital caliper question

[Tesoro]

I like to think of myself as a man of culture.

Seriously, though. I don't get why people get too fussed about units. Depending on the task, one tends to be more convenient than another. Usually, I prefer imperial units, because they're more tied to every day life - an inch is the width of your thumb, a foot is a foot, a yard is a step. Farrenheit is basically a percentage of how hot it is outside - zero is full cold, and 100 is full hot. Grains are super convenient for reloading. MOA is great for scopes. I find thousandths of inches more convenient than millimeters when machining metal. It's just the way the tolerances work out. For 3d printing, millimeters are king. Metric is better for cooking, but most recipes aren't metric in the US so I just deal with it. For every day use, radians are annoying (is that a 90 degree turn or pi/2 turn?)

I also hate that metric is all powers of ten to convert units. I find it confusing and lose track of decimal places, which can be a big problem. Any interesting math is best done with a calculator anyhow, so there's no real benefit to the whole "multiply by ten" thing. You can more easily tell that you did it right when the number changes rather than the decimal point moving.

I hear ya!

 

[Infrequent Shooter]

help with metrics

I dont know how I came about this, but once in a while it comes in very handy. Just thought maybe some people dont know it... Lets say you need a 6mm hole, and can't remember what size that is in english. Multiply by four and move the decimal two places to the left. 6 x 4 = 24, or .24...

www.practicalmachinist.com

good writeup.

 

[Infrequent Shooter]

I think I'll list some Remington 5.689mm BR bullets in the classifieds. They are the 3.36954 gram bullets that were so popular. Lol!

Grams are used by a lot of Ohaus check weights.

 

[Rocketvapor]

Just do the math.
25.4mm per inch is by definition the EXACT linear conversion,
Try it with the 6mm shortcut example and see what you get.
Had engineers that used the .3937 conversion factor.
For LARGE articles it caused errors.
0.03937" per mm is good for most measurements, but when measuring a rocket ship 50 meters long
39.3700787" per meter is closer



15.43234875 grains to grams, Use as many decimal places as needed.

My A&D EJ-54D2 allows me to pick the calibration point.
For the 22 gram low range I picked 10 grams. 154.320-154.325 grains displayed.

 

[Infrequent Shooter]

for gunsmith purposes, what measuring units are used?
metric, inches fractions or decimal?

 

[Rocketvapor]

I would hope that a competent gunsmith/machinist would be able to convert inches to mm and back depending on the equipment used.
Even to the point of applying material temperature coefficients (metric or imperial).
It's us home brew machinists that seem to have issues with the math.
As with most measurements, check with a suitable standard.

Seems we don't have a problem spending dollars on reloading equipment, but hesitate buying gage blocks, pins, ring gages, mass standards to check our work.

 

[gunsandgunsmithing]

for gunsmith purposes, what measuring units are used?
metric, inches fractions or decimal?

Most everyone will work in decimals. How many places depends on what you're measuring. Also, which tool to use for the job. If within a thou or so is good enough, calipers. If better accuracy is needed, a good micrometer.

 

[Rocketvapor]

Probably just as important as instrument accuracy is the human factor in measurements.
Being able to make repeatable measurements, verified with check standards, will show you what you can expect.
Here's a few instruments and a 0.250" pin and block.