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William Optics zenithstar 61 focuser locking screw thread size question


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Hello all

I wondered if anyone could help me identify the size/thread of the focuser shaft locking thumb screw that I somehow lost on my William Optics Z61.

It's the thumb screw that fits the top of the focuser, shown in the picture below missing (the white circle)

It seems to be an 8mm diameter but a metric 8mm (M8) bolt thread is too coarse.

I'd appreciate it if anyone can identify the size and thread or even a source of a replacement.

Thanks

Paul

19BB577D-3E82-4530-BC52-7675F0EEC2D4_1_201_a.jpeg

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There are two thread pitches at M8 - 1.25 and 1

If the bolt you tried had thread that was too coarse its probably an M8 x 1.25  - in which case try an M8 x 1

I would be very surpised if it was anything other than metric.

https://www.westfieldfasteners.co.uk/Bolts-Screws-Metric/Thumb-Screw-High-Type-M8x12-A1-Stainless.html

 

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1 minute ago, Sponcom said:

Thanks Billy, it looks like a very fine thread. I'll see if I can get hold of a M8x1.

Maybe try a cheap bolt from your local hardware store to confirm the thread before shelling out £13 on a shiny SS thumbscrew!

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I've done a quick measurement, seems like a 0.75 pitch, 1mm is too coarse. That bolt doesn't actually seem to do anything, focus lock I believe is done via the two smaller grub screws top and bottom of that larger bolt hole (one is under the OTA mounting ring). I just tried tightening the lower one and it didn't do much (didn't want to force it too much).

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Thanks All

 

the original one has a what looks like a teflon end to it. The thread looks very fine though so 0.75 is correct. I haven't had a response from WO but I have tried the screw from a friends Altair 60mm scope and it fits. So these are probably China generic and used on many different scopes and not just WO.

The bolt put pressure on the focus tube to stop it moving when a heavy load is connected. The smaller screws I thought were for alignment of the drawtube.

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I unscrewed the whole focus tube off. I think the large m8 bolt acts as a hold/semi stop on what looks like a plastic piece of material underneath it and the two grub screws so that if any are tightened it doesn't mark the focus tube, I think the large bolt simply stops the plastic piece from moving out of position when the focus is racked in and out.

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  • 1 year later...
On 01/04/2022 at 11:08, Sponcom said:

Hello all

I wondered if anyone could help me identify the size/thread of the focuser shaft locking thumb screw that I somehow lost on my William Optics Z61.

It's the thumb screw that fits the top of the focuser, shown in the picture below missing (the white circle)

It seems to be an 8mm diameter but a metric 8mm (M8) bolt thread is too coarse.

I'd appreciate it if anyone can identify the size and thread or even a source of a replacement.

Thanks

Paul

19BB577D-3E82-4530-BC52-7675F0EEC2D4_1_201_a.jpeg

Hello,

I was wondering if you were able to get the correct sized bolt. If so can you please share as I have the same issue?

 

Thanks

Maged 

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