[Metrology] How to develop a feel for measuring round rods with a micrometer?

WobblyHand said:
Measuring off lathe doesn't seem to be a problem for me. Just on lathe. If a kind soul could offer some insight, I'd greatly appreciate it.
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Since you're having problems on lathe and not off, it's might be useful to think of what your "technique" is when making those
measurements. My lathe has a nice flat headstock cover that makes a great armrest. When taking a measurement I always
do it the same way (if possible). I rest my left arm on the headstock and make mic adjustments with my left hand while supporting
the mic with my right. This keeps me stable, and allows me to focus on making the measurement without wobbling around while
I'm doing it. It seems a small thing, but it helps. Maybe you can develop a routine like that that makes your technique more
consistant.

I don't chase tenths very often, but when I do, I take a bunch of measurements. In the hobby environment, I don't think that's
unreasonable. Like the others said, everything matters, ie., it's not easy to measure tenths.

By the way, you said you have a crummy mic. Just curious, but what is it?
 
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BtoVin83 said:
Jesus you are moaning about being off on the fourth digit, when you get done building interplanetary spaceships you can join the rest of us building rock crushers
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This comment is neither helpful, nor constructive. Furthermore, the tone and tenor is not in the spirit of this forum. If you think chasing a tenth is a fools errand, that's your opinion. Others may differ.
 
If you want accurate readings do not remove the mic from the part to read the scale. Read your measurement with the mic in place on the part. This will prevent the mic possibly moving thus throwing your reading off.
 
Have you tried v anvil, ball tip or disc micrometers, they seem to work better for me. Also my scherr tumicos seem to have the best feel, the worst is a Vis I have. Another precise type is an indicating micrometer comparator.
 
Nogoingback said:
Since you're having problems on lathe and not off, it's probably useful to think of what your "technique" is when making those
measurements. My lathe has a nice flat headstock cover that makes a great armrest. When taking a measurement I always
do it the same way (if possible). I rest my left arm on the headstock and make mic adjustments with my left hand while supporting
the mic with my right. This keeps me stable, and allows me to focus on making the measurement without wobbling around while
I'm doing it. It seems a small thing, but it helps. Maybe you can develop a routine like that that makes your technique more
consistant.

I don't chase tenths very often, but when I do, I take a bunch of measurements.
Click to expand...
This is a great suggestion. I will check to see if there is some feature on the lathe that I can use as a rest or support. You are right, it can be the little things that can help a lot.

Ordinarily, I don't chase tenths, either. Only time I've done it successfully was when I had to indicate on a barrel bore. I'm just not that good at this, heck I'm really just a rank beginner. But when aligning a lathe, it does call for tenths, especially if you are making closely fitting parts. So finding little techniques to make it easier, and eliminating technique screw ups do help.

Actually, it's not necessary that one measures the correct value to the tenth every single time. (That would be a bonus.) What I do care is the measurements are tightly clustered about the true value. If they are, one can use averaging to advantage and measure things quite accurately with a few measurements. The wider the distribution, the more measurements it will take.
 
Canus said:
If you want accurate readings do not remove the mic from the part to read the scale. Read your measurement with the mic in place on the part. This will prevent the mic possibly moving thus throwing your reading off.
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Good idea. I'll try it the next time in the shop.
 
pacifica said:
Have you tried v anvil, ball tip or disc micrometers, they seem to work better for me. Also my scherr tumicos seem to have the best feel, the worst is a Vis I have. Another precise type is an indicating micrometer comparator.
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No I haven't. Only have flat anvils at the moment. The metrology section in my shop is not very sophisticated. As time goes on, hope to upgrade some things.
 
Sometimes the Mic it's self can be the problem. I have one that I can never obtain a consistent reading with. While a different mic. is consistent. Is it me or the Mic ? I don't know,but I will use the one that gives me consistent readings.
 
It my only 1-2" mic, so I'm going to have to live with it a while, or at least until I'm convinced it's not me. Come to think of it, both of my 0-1" mic's are a little easier. I have a 0-4" mic set, (0-1,1-2, 2-3, 3-4) and a different 0-1. So far, I think it's still me. But the feel of a larger mic is different than the little ones.
 
When measuring in tenths of a thou the surface finish can also play a part. I have consistent readings in the tenths on a ground and polished crankshaft, while a rough turned item my only show consistent readings of half a thou. The more measurements you make the better they will be. Chasing tenths can be a challenge . A tool and die maker once told me they worked in tenths while the machinists worked in thousands. Good luck
 
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