I made this Crayford style focuser using plywood scraps and surplus bearings. To test the concept I used a short piece of two inch PVC for the draw tube. I used my router to "mill" a flat area for better contact with the focus adjustment rod. I'll use an aluminum tube for the finished draw tube but for now the plastic tube works fine
The aluminum focus adjustment rod is supported by two bronze bushings that are in slotted holes in the focuser body. The two thumb screws push on the bushings to increase or decrease tension between the rod and the draw tube.
When making a homemade telescope mount or other project involving wood rings you'll probably have some wood scraps left over. Here is one use for some of them.
Clamp them together, or put something heavy on them till the glue sets up.
Start trimming
Do a little sanding.