Home Built 13" Jointer #14: Table Lifting Screw - Nut Assembly

This morning I set out to build the nut assembly that raises and lowers the infeed table.
I started with a piece of Delrin rod that I thought was 1.5” diameter.
Holding it with a handscrew, I marked the center and drilled a 3/8” hole through it.

I then took a cutoff piece from the screw to make a tap. I chucked it in my drill and while spinning, ground a taper on the disc sander. Then used an angle grinder to cut a rather sloppy flute in it.

Then chucked the tap in the drill press, and tapped the delrin by turning the chuck by hand.
This was very difficult for 3 reasons.
1) Poor quality tap. :-)
2) Removing a lot of material with 1 flute.
3) Delrin is slippery, and it’s hard to hold a round piece of it.

I could only do abnout 1/2 turn at a time, and had to back it all the way out to clear the chips.

Once tapped, checked the fit on the screw. Nice and snug. The reason I made it 1-1/2” long, was so that it would be on the tight side. The first 1/2”-3/4” of threads a bit loose, from running the tap in and out so many times.

I had some ideas in my head on how I was going to mount this, but thought of a better way this morning.

Whipped up some toolpaths in AutoCAD and carved out a slot to accept the nut. Except it wouldn’t fit. After a slight toolpath update and second run, I realized that the diameter was actually 1-3/4”, not 1-1/2”
Third time on the CNC was the charm, and I had a nice fit. Prior to routing the groove, I drilled 2 holes to locate T-nuts on the backside.

Then I clamped the nut to a block of wood on my CNC, and routed two flats, and drilled for the mounting holes that would line up with the t-nuts. I drilled a 1/8” hole, then countersunk with a countersink bit in a hand drill, followed by enlarging the holes by hand to 3/16” If I had a 3/16” collet for my cnc, I would have drilled them the right size to start with.

Screwed the nut to the base, and test fit on the screw.

Should work great. It’s nice and solid.

A few coats of paint tonight, and it’ll be ready to install tomorrow.

-- Gerry, http://www.thecncwoodworker.com/index.html http://www.jointcam.com