Thread: Optical Micrometers - A Chance Find in Alsace

Nice one bob!
I was considering that etalon Mic but hadn't looked at his other items in fear of going on a spending spree.....
Cheers,
_Ew

Wow those look like nice mics Bob just need to get my head around how they work.

Nice find BT ,

you might want a hair cut tho

Originally Posted by shedhappens

Nice find BT ,

you might want a hair cut tho

Been 20 years since I had a fringe Shed and I reckon 25 years before that that I had one that might have impaired my vision.

And Andre. The Alsace imports may need dissection and cleaning. A procedure that I would approach with trepidation and with camera in hand. If it eventuates I will share the experience.

BT

Originally Posted by Anorak Bob

The Y scale I have is metric but unfortunately the X is imperial.

Wow BT, that's paddling upstream a little...

Originally Posted by Anorak Bob

I will probably need some help with the LED conversion.

I think I might be able to help you a little bit there...

Regards
Ray

PS are those lamps 12v or 24v?

Originally Posted by RayG

Wow BT, that's paddling upstream a little...

I think I might be able to help you a little bit there...

Regards
Ray

PS are those lamps 12v or 24v?

Still upstream Ray but I feel I'm drawing closer to the shore.

I'm stumped on the voltage and I'm 6km from the 13. For some reason I was thinking 3V? I had purchased some "replacements" from Dick's and from memory (poor) I thought they were torch bulbs. The original bulbs were yellow and of a large diameter, about 15mm. A quick look for LED torches on Ebay revealed a smorgasbord. You can buy a torch from China with free shipping for a touch under 2 bucks. A torch shoved in the back of the thing isn't my idea of a nicely resolved solution but it would be a quick way of seeing if my idea of an LED replacement is feasible.

BT

Hi BT,

Do an ebay search for "E10 led" like this... E10 led | eBay

Choose your colour and voltage...

Regards
Ray

EDIT: See if you can determine whether or not your existing transformer is DC or AC, as well as what the voltage is.

Ooph! E10 LED bulbs! I know a Swiss Isoma microscope that is going to like one of those!

Greg

The micrometers arrived par avion in 6 days. Not bad. The condition of the pair was not flash. The exteriors were oily and dirty and sadly the oil had worked its way inside both micrometers. Dismantling was pretty straightforward. The lens in the centre of the graduated face, is mounted in an externally threaded barrel. This is used to retain the movable outer bezel and the fixed inner disc.

My understanding of how the device works is this - light from a bulb passes through the tiny objective lens via a 45 degree mirror ( the light uses half of the lens ). The focused illuminated image is projected by the other half of the lens onto the series of inclined mirrors which correctly orientate the image which is displayed on the ground glass screen. The screen is attached to a spring tensioned dovetailed slide. The post ( cam follower ) on the slide bears against the cam which is in turn fixed via a pin to the outer rotatable bezel. The eccentric or ramping on the cam is such that one complete rotation of the bezel equals 1mm of travel. The enlarged image enables an enables any engraved line on the scale to be located between the parallel lines on the focusing screen.

The abrupt step in the cam causes the screen to rapidly return the original starting point and another millimeter can be measured. Accurately.

Say the table ( if the micrometer is mounted on the X ) is to be traversed 0.07mm. The scale, the position of which is adjustable, ( there is a spring loaded thumbwheel that provides axial adjustment ) is moved so that a graduation aligns with zero on the bezel and lies between the two parallel lines on the ground screen. The bezel is then rotated to read 0.07mm in relation to the zero mark on the inner disc's vernier.
When the table is traversed to a position where that same graduated line on the scale is again between the parallel screen lines , the table will have moved the exact 0.07mm.

The light bulbs and their replacement are something I will seek advice about in another post. The French found a way of complicating their mounting.

BT

ps. Because of the problem I encountered with uploading my photos I opened a Photobucket account. I can copy and paste but the photos are large. Anyone interested enough can view the photos here -

bobthomas52's Library | Photobucket

They are out of order.

Hi BT,
Almost forgot this one.

Originally Posted by Anorak Bob

The abrupt step in the cam causes the screen to rapidly return the original starting point and another millimeter can be measured. Accurately.

Dont you mean "return the original starting point and THE SAME millimeter can be measured"? I wonder if you are only meant to turn it one way so there are no backlash errors?

Originally Posted by Anorak Bob

Say the table ( if the micrometer is mounted on the X ) is to be traversed 0.07mm. The scale, the position of which is adjustable, ( there is a spring loaded thumbwheel that provides axial adjustment ) is moved so that a graduation aligns with zero on the bezel and lies between the two parallel lines on the ground screen. The bezel is then rotated to read 0.07mm in relation to the zero mark on the inner disc's vernier.
When the table is traversed to a position where that same graduated line on the scale is again between the parallel screen lines , the table will have moved the exact 0.07mm.

Thats in incremental mode. You should also be able to use it in absolute mode.

Stuart

Originally Posted by Stustoys

Hi BT,
Almost forgot this one.

Dont you mean "return the original starting point and THE SAME millimeter can be measured"? I wonder if you are only meant to turn it one way so there are no backlash errors?


Thats in incremental mode. You should also be able to use it in absolute mode.

Stuart

Glad you looked at this Stu. Whilst probably bordering on being too esoteric, I thought if anyone it would be you that might have an inkling of interest.

I struggled a bit with my description. You are correct, the instrument reads the same millimeter again. The cam does funtion more smoothly when rotated anti-clockwise. There is no discernable backlash. I was hamstrung the other day with the picture posting glitch. A few more photos may help.

BT

Hi BT,
My theodolite happens to work along the same lines.
I wouldnt have expected much backlash in that gear. Did you try lining up the line on the machine from both directions? Any slop dovetail would lead to an error. But given the amount of slop there is likely to be in gear from that part of the world and the amount of slop I think you'd need to give an error worth talking about , I guess its a none issue. Just as long as you're aware it will measure 100.07mm just as well as it will measure 0.07mm.

Oh that reminds me I have a thread to post, I didnt bother when I saw people having issues.(one of these days I have some more posts if they ever get the old thread problem fixed)

Stuart