Crayford focusser for finder scope

[savarin]

Started with a bunch of these

to make a bunch of these

One of which was faced on both ends then squared on two sides then drilled for a 4mm shaft.
Then mounted off set in the 4 jaw but only using 3 of the jaws and bored out to just enter the side of the 4 mm hole.

It was then mounted between a pair of mandrels to turn off the surplus.

leaving this small curved part.
The 6mm angle has 4 x 10mm bearings that the focusser tube slides against.

These are then bolted to a small plate

A tube to hold the eyepiece is added

Then mounted to the finder scope tube

The 4mm stainless shaft moves the tube in and out by friction alone.

 

[BaronJ]

Hi,

Nicely done. Could do with some blacking to cut down reflections.

 

[savarin]

The inside is fully blackened. I use artists Atelier carbon black, its the blackest black I've found to date.

 

[rwm]

Very slick. Is there a way to adjust the fit of the tube or do you just have to get the diameter right?
Robert

 

[dtsh]

Nice, now you have to make a dual speed crayford.

 

[savarin]

I made this one to the exact size but did place a screw and pusher to press the shaft against the tube but in practice it hasnt been required.
I may make a dual speed for my bino when I get that far and will use three balls pressing on the main shaft held with a cone.
Turning the main shaft is the coarse feed and turning the cone is the fine feed utilising the three balls as a planetary gearbox/drive.
I made a simple test and it worked pretty well.

 

[BaronJ]

The inside is fully blackened. I use artists Atelier carbon black, its the blackest black I've found to date.

Thank you, I did wonder what you used.

 

[savarin]

some results here
https://www.hobby-machinist.com/threads/80mm-long-focal-length-refractor.26212/page-3
post 77