Thursday, January 29, 2026

Threading

I tapped the collar on the extension tube for a 1/4"-20 thread but the appropriate thimbscrew did not lock the eyepiece securely. Why?

The collar is about 1/4" thick and thst is not enough threads to clamp down adequately I persuaded myself.  So I did an 8-32 thread and it worked.  8 threads instead of 5.

UPDATE: Another disappointment: the thumbscrew holding the extension tube in the tube interface does not hold it in place square to the interface.   I think the problem is that interface flange is only .5" wide and that is not holding it square even though it is very little difference in ID and OD.  I think the interface should be 1" wide.  I have no 1" thick pieces from which to start.  I do have a  5" thick piece of CFC that I can laminate into a 1" thick piece. 

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