Upgrading an old Supermicrometer



Hi everyone; after browsing this site for months, I've found my first question that didn't already seem to have an answer...

I recently found an old P&W Model A supermic hiding in my company's archives, which I am currently having calibrated by an outside lab. It is the mechanical type, with resolution down to .0001" and I was wondering:

Is it possible to attach a gage amplifier/LVDT to this model of supermic to increase its resolution/accuracy?

I'm in charge of verifying/calibrating gages for my company, and frequently, I'm dealing with tolerances of .0001 or less. Until I took over this post the solution to the problem of lack of resolution/accuracy was to shrug and say "it's good enough," but if I can get the ratios down to a more reasonable level, I'd like to do so. Pratt and Whitney will not retrofit it to the electrolimit model (I asked), so if I want this thing to get below .0001", it looks like I'll have to do it myself.

I strongly doubt I'll be able to get approval for a newer supermic or bench mic in the next couple of years, but I might be able to squeeze in a thousand or two for an amp/probe if it can be done.


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This does not answer the specific question, but may become an option. As I was looking through one of the sales catalogs the other day I ran across this.

Super Micrometer

It has an accuracy of .00002 (20 millionths) and only costs around $1,500 (ok, I should not have said "only costs around" but you did indicate that you may be able to spend $1,000-$2,0000).

I assume you can find it cheaper, the link is just to give you details on the item itself.


I had seen that one, but unfortunately, for my purposes, it has 2 drawbacks:

1: limited range of only 0-1"

2: measuring force is not adjustable and set at 7-9 N, meaning it can't meet the force settings in ASME B1.2-1983.

I check thread plugs from 6 TPI all the way through 56 TPI, so ideally, I want calibrated settings at .5, 1 and 2.5 lb of force, and a range of at least 0-4".

The supermic only has 1 and 2.5 lb settings, but I think I could use a calibrated load cell and force gage to get it to measure at .5 lb when required


Alternatively, it looks like the tailstock unit can be swapped out pretty easily, so if anyone knows where I might be able to get my hands on an electrolimit tailstock, or even the whole supermic, that would work, too, as I've seen plenty of the mechanical ones selling for well under $1000
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