RASA focuser thread

[rogerg]

Hi all,

Does anyone know the size and pitch of the thread on the Celestron RASA focuser threaded rod?

The thread I mean is the threaded rod that is attached to the mirror cell. If you swap focusers (eg to install the motor focuser) you see the threaded rod.

I have one that has some damage to that thread so I am looking to find tools or nuts to suit, to clean up the thread.

Thanks,
Roger.

[JA]

You could possibly use a universal type external thread repair tool, like one of these....

https://www.amazon.com.au/NES1A-Universal-External-Thread-16-Inch/dp/B00D8WJ1FC

Best
JA

[rogerg]

How interesting, I haven’t come across those before! That is a good fallback to try if nothing else. I wonder how easy it is to make the situation worse rather than better :lol:

[JA]

Do you have the threaded rod out of the scope? If so you could measure its major diameter with a set of digital calipers or micrometer and from that you'd get a reasonable guide to the thread. Or go to a specialist bolt supplier with the threaded rod.

You can also repair a thread by hand if you are very careful with a very small triangular fine file, just don't spend to long on the same spot, otherwise you'll create a flat- keep the file moving around the circumference of the threaded rod (where the damage is) tracing a path around the thread helix as you go.

Best
JA

[rogerg]

I haven't manged to detatch the threaded rod from the OTA. I suspect they are permanently attached or at least removing it requires signifcantly more disassembly of the OTA. I cannot see inside enough to see if it should unthread.

I'll have to retrieve my calipers from where they've disappeared and work out the specific details. Also talking to a few more people it seems a good approach would be going to a bolt and nut specialist with the nut from the rod and try to get a matching nut stronger than brass. or a cutter or Die kit ... new territory for me.

I'm not great with precision at such fine scale so won't attempt using a file myself, I think I'd likely do more damage :)

Thanks,
roger.