1840's telescope

[Mitch Alsup]

A very old telescope has come into my possession in order to be repaired back into working order. I would like to leave the telescope in 1840's condition while restoring its functionality to new.

I have two problems I don't quite know how to deal with::

a) A large (2.3") narrow pitch thread (~1mm) in what appears to be 0.030 brass that has been enlarged such that it no longer fits with it's other mating side. I need to make one end bigger or the other end smaller without marring the brass or harming the threads. Only a dozen thou of alteration seems necessary. Anyone have an Idea as to how I can do this?

b) a brass bushing soldered to a threaded cap has broken its solder joint. The bushing has several obvious an purposely positioned indentations that I assume are there to set tension on the bushing as the telescoping tubes extend and compress. I can solder the tube back, but it is riding on the tube that slide on it roughly and I should like to take the indentations out, set the sliding fit, and then adjust tension. Any comments on how to reduce the indentations without marring the brass?

Pictures when I get around to them.

 

[homebrewed]

a: You might try wrapping fine thread around the brass piece with outside threads. Or you could try some plumber's teflon tape, if sewing thread is too large; or perhaps a strip of the cheap half-mil-thick painters drop-cloth. No adhesives, no additional machining is needed if one of these work. If none of these work, you might consider filling the outside threads with epoxy, then re-cutting the threads. Since the threads have worn anyway, you might be able to cut new, properly-fitting threads without getting down into the original brass. Maybe. Or for yet another approach, a thin conformal coating of epoxy might enlarge the threads enough -- but it would be difficult to get the coating thickness right. Maybe . Do you detect some caveats? Definitely!

b: I'm not sure where the indentations are to help with this one. Photos _would_ help.

 

[Flyinfool]

If I am understanding correctly? The part with the male thread is is a piece of brass tubing with about a .030 wall. Is the mating part with the female thread also .030 tubing?

Is the loose fit due to wear, or due to the tubes stretching and getting bigger or smaller?

If both are tubes can you use something like a muffler pipe expander and/or collet to squeeze or expand them back to the correct dimensions.

I agree, lots of pics would sure help us visualize what you are trying to do.

 

[extropic]

Helpful replies when I get around to them.

 

[Mitch Alsup]

If I am understanding correctly? The part with the male thread is is a piece of brass tubing with about a .030 wall. Is the mating part with the female thread also .030 tubing?

Is the loose fit due to wear, or due to the tubes stretching and getting bigger or smaller?

The loose fit is due to being dropped, sometime in the 1920's and the scope has never worked properly thereafter. It is an heirloom piece for the family. At one point in time, the telescope was used as payment for a doctor assisting with a birth in the family, and several years later the family bought it back in an non-working state.

I will get pictures, probably monday. It is a nice piece of machining for 1840's.

I did get the scope to focus, after I found the frozen telescoping-tube.

Now I need to re-solder a nut-to-bushing, and maybe roundify several tubes so it slides evenly with moderate friction and remains stable.
The lenses will be cleaned with utmost care and delicacy.