Thread: Chasing a suitable spring or spring material for a microscope eyepiece clamp.

I recently chanced upon and purchased a cheap microscope micrometer eyepiece. It was cheap because the sleeve required to secure the eyepiece to the scope's head was absent.

The eyepiece features an internal 0.1mm scale and 0.01 vernier. The scale requires calibration against an engraved (or etched ?) glass slide called a stage micrometer. To facilitate this calibration the eyepiece is fitted with a focusing collar and scale under the main body. The missing sleeve is fixed under the collar with three M1.6 screws. The chrome tube slides inside the microscope head's black eyepiece tube and the missing tube is a close sliding fit down the outside of the 25mm diameter eyepiece tube. A clamp is required to prevent the micrometer eyepiece from rotating in the head tube. A standard eyepiece rotates freely.

A number of scope makers use a simple split clamp to secure their micrometer eyepieces and Nikon use split clamps on one end of their camera adaptor for the old S model scope such as mine. The other end of that same adaptor features a clamp similar to that incorporated in my missing sleeve. The clamp consists of a radial thumbscrew bearing on a incomplete ring of spring steel housed in a recess in the sleeve's bore.

I had entertained the idea of using the camera adaptor's split clamp to hold an abbreviated sleeve but the flange on the adaptor obstructs access to the focusing ring, unfortunately.

So yesterday I started work on a sleeve incorporating the spring steel ring. Which brings me to the point of this post. The spring.

I have two camera adaptors, one utilises stainless for the spring the other, blued steel. I have seen another similar type clamp with a brass spring. The internal diameter of the spring would probably be 25.5mm, sufficient clearance hopefully to prevent scratching of the black painted tube. It's width, 5 - 6mm and thickness, about 0.5mm based on the size of those in the adaptors

I looked online for clock mainsprings but they are expensive and too big. I had a look at a Bulldog clip but the largest I have is too small. I could probably turn and bore a piece of 4140 but I imagine it will "spring" one way or the other when a section is cut away.

Does anyone have any suggestions?

Here is the purchased eyepiece -

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And another complete with sleeve -

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The camera adaptor's split clamp mounted on the eyepiece tube and the cramped access to the focusing ring -

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The camera adaptor showing the spring in place and removed -

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And sort of how it would look albeit without the sleeve -

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Bob.

Maybe a piece of stainless/other shim stock cut to size? Seems pretty springy as it leaps uncoiled threatening to slice and dice..

Bob, I have plenty of 0.4mm thick SS sheet left over from taking apart clothes dryer drums if that is of any use to you?

Var, Bob.

How do you reckon I would go rolling the stuff ? Would it want to kink?

I was just thinking that maybe a tubular insert of Delrin might work. The wall thickness of my sleeve is at present 5mm. I'd need at least 4mm thickness for an M4 thumbscrew. 1mm thick plastic might be too thin?

BT

G'day Bob,
I've used sections cut from an old tape measure spring for a number of different jobs.
They are generally not stainless but if that is not a major priority you can cut and grind a section to the desired shape.
They can also be annealed and re heat treated easily enough if you need to bend it.
Cheap too, a $2.00 tape measure will yield a lifetimes supply.
Cheers,
Greg.

Hi BT,

I have 20 thou and 15 thou 1095 spring steel sheet. I've never tried rolling it. I can send you some if you want.

Ray

Originally Posted by Anorak Bob

Var, Bob.

How do you reckon I would go rolling the stuff ? Would it want to kink?

I was just thinking that maybe a tubular insert of Delrin might work. The wall thickness of my sleeve is at present 5mm. I'd need at least 4mm thickness for an M4 thumbscrew. 1mm thick plastic might be too thin?

BT

It seemed to roll nicely on a large scale
Transition.jpg

Transition1.jpg

I cut a piece of that SS with snips and it of course wants to curl but it's easy to bend back into a flat strip
It still has some spring to it as demonstrated by this 20% sprung to unsprung change in diameter.


SSstrip.jpg

Thanks for the suggestions and offers Greg, Ray and Bob.

Given that Bob lives only a spit away I might lean on him for a scrap of stainless. I measured the stainless spring properly with a ball anvil mic and it is 0.3mm thick x 5.3mm wide. The black spring is thicker, either one could possibly be a replacement.

I will send you a message Bob.

Bob.

I have some blue steel shim in various thicknesses up to 0.8mm. A piece of that can be sent easily.

Michael

Originally Posted by Michael G

I have some blue steel shim in various thicknesses up to 0.8mm. A piece of that can be sent easily.

Michael

Thanks for the kind offer Michael but let me see how I get on with Bob's recycled dryer stainless. I will probably know tomorrow afternoon.

Bob.

You know that 1/2" wide black steel strapping used on serious boxes?
Works very well as a spring, can be cut with HEAVY shears, rolled and ground.
I had to make a very similar spring for the dial on the saddle of my lathe after the old one went airborne...

Cheers

Hi Bob
You dont indicate how much room you have got but how about copper/beryllium fingerstock or pieces of feeler guage strip?

Roger

I called in at Bob's yesterday and scrounged a slice of his stainless steel. I cut one edge with a large pair of Gilbow snips and draw filed the edge flat. Then I scribed a line parallel to that edge with a height gauge. I couldn't use snips because they would kink and twist the stainless so I used a piercing saw. It has been a long time since I tried cutting a straight line with a jeweller's saw and the result wasn't flash but a bit of filing removed evidence of the poor workmanship.

The stainless was not stiff and was easy to saw and file. To form the "spring" I used a piece of 25mm bar as a mandrel and rolled the strip of stainless by simply turning the chuck with the outer end of the strip held taut with vise grips.

A dummy sleeve facilitated test fitting resulting in a satisfactory fit, one the won't damage the finish on the microscope tube. Fingers crossed!

All that is left is some accurate drilling and tapping of the real sleeve along with the boring of the sleeve to accommodate the spring.

Thank you all for your kind offers and suggestions. And thanks again Bob for the stainless.

BT

Hi Bob
Nice work and great pictures, looks just like a bought one.
Bob