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Depth micrometer usage

Some help please. I'm trying to use a depth micrometer to establish the register of the groundglass focusing screen in an old camera. The glass is held by spring clips so it's quite difficult to tell when the micrometer's rod has just touched the glass surface. If I can establish this dimension, I'll try a similar measurement on the film holder. In this case the surface is thin, ribbed metal sheet which again could flex slightly before my fingers are aware of any resistance. (I don't have any problem using the depth micrometer against hard, unflexing objects.) Any ideas please - many thanks.

(I've googled but the examples seem to concentrate on checking the micrometer against hard steel reference pieces. I also have a small clock gauge but no means of holding it firmly.)

Reply to
Malcolm Stewart
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How about shining a light at an angle to the surface to be measured. When the surface is touched by the micrometer the reflection will be deflected.

Cliff Coggin Kent UK

Reply to
Cliff Coggin

Trap a slip of VHS or audio tape between the micrometer tip and the workpiece. If necessary, weight the tape with a tiny piece of chewing gum. When, on unwinding, the tape drops away, the micrometer tip is a consistent 1/2 thou away from the workpiece.

Jim

Reply to
pentagrid

Thanks for the suggestions - I tried removing the ground glass and found that it was mounted on lugs, so I measured between these and the reference surface. It was well within the published specs. & tolerance. Now for the film holders...

Reply to
Malcolm Stewart

Film holder = metal Depth micrometer = metal

Solution = metal + wire + battery + bulb (when the micrometer touches the film holder the electric circuit would be completed and the bulb should light up)

Do not use your mains supply - you would shockingly discover that this warning is very true.

Hope this helps Louis

Reply to
Pete

Thanks Film holder = metal = true Depth micrometer = metal = true but film holder reference surface is varnished black and a quick check with DVM shows resistance = infinity.

My reason for establishing the dimension is that my camera is from an era (~

1955) when English standards were giving way to "International" standards, and before I buy any more film holders, it would be wise to know what era I'm looking for. (Measurements with a digital caliper gauge have been easy to make, but have so far provided puzzling results, ~0.3mm higher than expected with a large SD, - perhaps I'll have to resort to doing it optically.)
Reply to
Malcolm Stewart

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