Just for the heck of it I picked up some one inch black pipe nipples at HD yesterday to see if I could make a cheap multi-length rest for my Jet 1236. The diameter of the pipe is about 1.035" OD and needs to be about .99" to 1.00 to fit the banjo. I used my grinder and 1" belt sander to get the post there. I also flattened the upper flange of the elbow on both sides.
I had intended to pin or weld the post to the elbow but have not as yet since I have had no problems with it loosening, but I may still do that just to be safe. The rest itself is not likely to loosen and can be replaced with various lengths. I have only tried a 5" (made from a 6" nipple) so far. I was going to epoxy a 5/8" rod or larger rod into the id of the post and rest, but I have used it a couple of times now and it seems plenty rigid. I will definitely add an insert into the post and any longer rests. I have 4", 9" and 12" nipples yet to be tried. I may drill a tranvers hole for removing the rest with a tommy bar.
The picture shows the post at 3 3/8". That should fit a Jet 1236, Delta and HF. Others with 1" posts may require different lengths. Screw everything together first and mark the post for cutting with an angle grinder and cutoff blade by matching the length from the top of your existing rest to the bottom of the post.
I was going to try using some 1" bolts and nuts I have, but the 1" bolts were only .945" diameter.