Megrez original focuser

[Leo.G (Leo)]

I have an 80mm Megrez original model semi APO telescope here of which I've just stripped down the original focuser to replace worn bearings and remove slop.
The focuser has a plate/tag which shows "J&R Optical co.LTD-Megrez 80mm aperture. 480mm EFL. F/6SD"
I can't find any information on this focuser, single speed unit.
I could replace it with a 2 speed WO focuser I have here if I machine up a 90mm threaded collar but it's way too cold to go play in my garden shed where the lathe lives.
My issue, upon stripping the unit down last night I noticed besides 3 of the 4 tiny 693zz (3mm ID 8mm OD 4mm width) bearings were locking up/grabbing in places, hence some wear marks down the tube but what else I noticed is under the bearing plate someone has put double sided tape. This made it hard to get the bearing plate out originally and I'm betting it would not be manufacturing standards as tape thins out with age.
This has me thinking MAYBE a previous owner changed it with non original parts and the focuser originally had the tiny 623ZZ bearing which is 3x10x4mm and the tape took up the extra 1mm by fitting the smaller bearing.
I've bought a pack of ten 693's from a local bearing supplier after stating he wouldn't have what I needed (ordered and never collected he said) and he's getting me a pack of 10mm OD 623's in within the next week or 2 ($20 worth of bearings and $20 freight if I can't wait).
I'm trying to find original specs/parts drawing of this unit.


It doesn't matter, I'll remove the tape and fit 10mm bearings when I get them and if it's too tight I'll put new double sided tape I'll measure up (or a brass shim of the exact size that won't thin out with age/use) and fit the 8mm 693.

[Leo.G (Leo)]

It seems this is no longer that important since I found the 2 dual speed GSO ball track focusers I have for my 8" carbon RC screw straight on the Megrez tube (I always thought the RC had a larger collar) and I Also have an extra 4 inches of extensions whch probably will be needed because it's a much shorter focus system with the RC8 thing fitted.
I still want to tidy up the original Megrez focuser but if I buy a couple of more extension collars I can use it with the RC as a finder/guide scope (I do this with my 152mm refractor).


I've rebuilt the original with new bearings and some attention and it's reduced the slop considerably towards zero (never going to get zero with the weight I hang on it, I'll use that focuser for visual and heavier duty things for imaging). I also have a very nice WO focuser which I've designed an adapter so it will screw straight on with a longer central tube than the original or the RC focuser. I just have to find the aluminium to machine it up and remember how to dodecent threads on alloy on a lathe (my book will tell me but I don't have enough alloy to mess it up a few times). In all fairness I haven't really used a lathe in well over 20 years other than a few very small jobs in the past couple of years, no threading though.