The Home Machinist!

In recent tool buying choices I decided to buy a height gauge again.
A nice Mitutoyo vernier 12 inch.
It got me thinking and now I'll wonder out loud.
Is it possible to get measurements better than .001" tolerance?

wally318 wrote: ↑Sun Dec 02, 2018 1:13 am Is it possible to get measurements better than .001" tolerance?

Strictly my opinion.
Resolution is the term I'd use.
Depends on the nature of your setup, and what you're inspecting, assuming that's how you're using the height gauge.
For layout?
Not a chance.

For inspection purposes, if you use a good tenths indicator, and have a respectable surface plate, and an accurate angle plate, you may be able to discern as closely as a tenth, but that won't be by reading the display. If you use gauge blocks or a device like a Cadillac Pla-Chek, you should be able to do better than a thou.

H

So If I'm understanding you correctly .... To get an accurate height you would use the height
gauge with a tenths indicater mounted on, and reference off stacked gauge blocks and the indicator
would give the finer resolution?

Correct. If you're not familiar with the Pla-Chek, it's really the easiest way to do so, however. Think of it as a supermicrometer standing vertical. It has rings @ 1" intervals and is calibrated in tenths. You pick up a given feature on the part you're inspecting, setting the indicator at 0, and then get a reading from the Pla-Chek, which reads the distance from the surface plate.

Where I was trained, that was common procedure (late 50's, early 60's), so each inspection station was so equipped. Inspection favored Interapid indicators. I suspect that, today, it's an obsolete process, although still viable.

H

Thanks.

My pleasure. I hope it helps you understand how tight tolerance inspection was once accomplished.

H

This sort of thing is too sophisticated for my ham-fisted abilities, but I like learning about it anyway.
So thanks from me too.

Methinks that a good quality vernier gauge such as Mitutoyo can be read to 1/2 thousands because of its widely spaced scale markings.

As Harold stated above you need a good quality surface plate plus angle plate etc. etc. Also a surface gauge to mount your good quality Test indicator on.

Use the Test indicator to pick up the feature on the work piece you wish to measure and adjust the indicator to read zero. Move the indicator to the height gauge and adjust the gauge until the indicator reads zero again. Now you can read the actual dimension off the vernier scale. To get better than one thousands use a magnifying glass and see which adjacent two index lines are equally spaced -more or less- from the opposite main scale lines. Carefully done one can estimate dimensions within .00025 (a quarter thou) I believe. But, and it is a big but, this all depends on the accuracy of the vernier scale and your ability to estimate the location of the index lines vis a vis the main scale lines. One half thou should be possible, though. w

I'm having a bit of difficulty visualizing your process. If you are measuring from the surface plate to the bottom of a feature, then I can see how your procedure can work. If you are measuring to the top of a feature then I have difficulties. Any height gage I am familiar with does not have a 'top' surface to transfer the indicator reading to. I suppose a special fixture could be made to replace the clamp-on scribe to do this but I have never seen one. A Pla-Chek is another matter, because IIR both upper and lower surfaces of the disks can be used.
Please educate me on how you do the transfer to a Vernier Height gage when measuring to the top of a feature.
TIA
--earlgo

earlgo wrote: ↑Tue Dec 04, 2018 9:27 am I'm having a bit of difficulty visualizing your process. If you are measuring from the surface plate to the bottom of a feature, then I can see how your procedure can work. If you are measuring to the top of a feature then I have difficulties. Any height gage I am familiar with does not have a 'top' surface to transfer the indicator reading to. I suppose a special fixture could be made to replace the clamp-on scribe to do this but I have never seen one. A Pla-Chek is another matter, because IIR both upper and lower surfaces of the disks can be used.
Please educate me on how you do the transfer to a Vernier Height gage when measuring to the top of a feature.
TIA
--earlgo

Clamp the scriber, upside down if necessary, or a small tool bit blank, to the measuring surface of the vernier gauge.

Then use the top surface of said scriber/tool bit to locate the test indicator tip on. This top surface is then identical in elevation as the vernier gauge bottom surface, from the surface plate. w

Your height gage must be different from this. The bottom of the scriber holder is most likely not able to be zero if it were able to reach the surface plate. Adding a tool bit or gage block would still not fit your description. Turning the scriber over would not work either.
Am I not able to understand your explanation? Maybe I pulled an incorrect picture of a VHG.
Perhaps a picture would help?
--earlgo

Wolfgang that may be okay for you in your home shop but it wouldn't fly if you worked as a quality inspector like I used to. You had to use the appropriate tools. No hair splitting permitted. I still do it this way for the stuff I hack out for myself.

When I worked I used height gauges and an indicator to get a zero and then transfer to gauge blocks or a height master to get an actual number. That sort of thing is usually done now with a CMM but there are times when it is quicker to do it the old fashioned way. It's a good technique to have in your skill set.

Pete