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Old 25-07-2021, 09:03 PM
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rogerg (Roger)
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RASA focuser thread

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.
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Old 25-07-2021, 09:13 PM
JA
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You could possibly use a universal type external thread repair tool, like one of these....

https://www.amazon.com.au/NES1A-Univ.../dp/B00D8WJ1FC

Best
JA
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Old 25-07-2021, 09:47 PM
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rogerg (Roger)
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How interesting, I havenít 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
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Old 26-07-2021, 08:40 AM
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Quote:
Originally Posted by rogerg View Post
How interesting, I havenít 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
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.

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JA
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Old 26-07-2021, 01:17 PM
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rogerg (Roger)
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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.
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