Hadley Adapted FuseBridge 1.25" Focuser

UPDATES:

Added version with mounting screw holes countersink so knob does not collide with screw head for those using full sized screw heads.

This focuser is based on the Crayford design, where a smooth pinion is rolled along a smooth drawtube, and the friction between them allows you to focus the eyepiece.

This focuser uses standardized hardware that is affordable and very common in hardware supply stores. The cheapest way to construct this focuser would be ordering the appropriate hardware from Aliexpress. . 

A hardware list from Mc-Master Carr is included so you can verify specifications before getting hardware from cheaper sources. 

The drawtube itself is made of extruded Polycarbonate, if the length of the tube is cut to 68mm long the focuser travel will be 1.5". Of course you can select a different length for your application. I recommend scuffing the outside of the drawtube with 350 or finer grit to minimize reflections and improve motion.

See photos for assembly.

You will only need 4 3D Printed components for this focuser:

1 Main Body-Hadley-focuser

2 Turn Knob Fixed

1 Drawtube Bottom and top Ring

Hardware Components:

2 Bronze bearings

4 3x8x3 bearings

8 M3 washers/ 4 M3 nuts

3 M4 Nylon screws

1 M4x80mm Dowel pin, Stainless steel

1 1.25"ID x 1.5" OD PC tube, your desired length

2 M3 Grub screws

4 M4 8mm screws

Note: assemble the 4 bearing screws shown to the right with a M3 nut in the slots.

Shaft, Knobs, and Bearing assembly

2 Nylon screws provide tension against the shaft.

Attach the Focuser as you would a regular Hadley Helical Focuser.

For those of you not using low profile thin head bolts there is a STL model with a countersink so the heads of the bolts don't collide with the focuser knob.