2" Crayford Focuser

Crayford Focuser 2inch by jackleone12 - Thingiverse

Found this focuser over on Thingiverse and re-engineered it for the Hadley project. It is far superior to my rack and pinion design, smooth operating with no grind or slip at all. Has about 40mm of travel, which is way too much really for simple visual use, but let's you mess around with photography if you want.

I tweaked it to fit the remixed UTA that I designed for the rack and pinion focuser, so no need to redo that. I've included that model here again. Most of what you need to know is over on the original design if you go over there, but there were a few problems I had to address and some missing details that I've included below.

What I changed:

1. Remixed the base plate to fit the revised Hadley UTA posted originally with my rack and pinion focuser (UTA design included in the files here).
2. The original design, while supposedly for 2" eyepieces, was inexplicably too small to accept a 2" ERP, so I got that squared away. I've included a bushing for 2" to 1.25"
3. Simplified the designs using the slicer so they would load into my design program
4. Added spacer/shoulders to the dials. The original dials would twist slightly out of line with the pinion shaft when you tightened the grub screws. I eliminated that twist and also spaced the dials that were rubbing the body, by adding shoulders.

The Hardware:

1. Bearings are 12mm OD x 6mm ID x 4mm bore
2. The axle is a 4mm stainless steel shaft 100mm
3. The bearing bolts are M6x16 hex head cap screws (they self-thread into the plastic)
4. The dials use M4 grub screws
5. The pinion axle tension screws are M5 and you can use whatever you like there
6. The cap screws are an M4x20 countersunk head screw (self-threading)
7. I tapped in some #10x24 vinyl screws for the eyepiece holders, you could use whatever you like there. Tapping lets them spin easily.

I believe everything else is pretty well spelled out over on Thingiverse so check it out.