I've done this  where I formed the pitch with a blade and then finished in a lathe. I rather like this approach

 

 

Interesting.

Quite the operation.  Next we need a nut. 

8 hours ago, HandyDan said:

Quite the operation.  Next we need a nut. 

Yep.  I'm a bit nutty, but running around and around and around a stick would make me dizzy.

A teacher's screw up tale:  I had a student who wanted a bedside table with a top that could rotate from bed level to bed tray level with a 90 degree turn. About 8 inches of lift required. I helped her cut a two parallel spiral slots around a 4"ish wood cylinder using the rotary axis of our CNC. It fit inside a PVC pipe with a 4" i.d..  Bolts through the outside held skate bearings that rode in the slots. A spring loaded pin could be pulled out to let the top rotate, then let loose to lock it at whatever position it was in.  The base was a  tilted conical shape of stacked BB plywood layers cut on the CNC. The idea worked brilliantly and made a very unique and beautiful side table.

4D  

@4DThinker Wonder if you have any pics of that table?

 

Like Dan that is a cool video but what is the screw for without a nut?

 

ok so just checked and he also made a video for the nut.

 

Here is the nut

 

 

Edited April 20, 20224 yr by Gerald

4 hours ago, Gerald said:

@4DThinker Wonder if you have any pics of that table?

I'm sure I do.  Spent the day looking through the several years of student project photos and haven't found images of that project yet.  I did find a photo I took of a blue metal rectangular can that had several SD cards in it which I barely remember and haven't come across yet.  My guess is that somewhere on one of those SD cards is where that project images resides. 

4D.  Still looking.

On 4/20/2022 at 8:21 AM, 4DThinker said:

The idea worked brilliantly and made a very unique and beautiful side table

She did go to college  for Mechanical Engineering I hope

6 hours ago, Cliff said:

She did go to college  for Mechanical Engineering I hope

Never sure unless they tell me.  The Furniture classes are part of an Interior Architecture and Product Design degree.  We do get the occasional transfer from the engineering college.  We also occasionally get students who are the children of one or two engineers and can't help but be a bit more mechanically inclined than normal. 

4D

Photos found.  Not sure the table was completely done when these were taken, but they do show the up and down positions as well as the threaded shaft. 

2 hours ago, 4DThinker said:

Photos found.  Not sure the table was completely done when these were taken, but they do show the up and down positions as well as the threaded shaft. 

Now  that's pretty darned cool.

3 hours ago, Gene Howe said:

Now  that's pretty darned cool.

Thanks Gene.  One thing we never have a shortage of is creative students. Seeing the photos again I remember that the spiral slots went flat at the bottom to keep the top high. The top rotates 270 degrees from low high to position.  

4D

11 hours ago, 4DThinker said:

Photos found.  Not sure the table was completely done when these were taken, but they do show the up and down positions as well as the threaded shaft. 

I go with Gene pretty darned cool. Now we can use the thread cutting riuter jig to make our own table

10 hours ago, Gerald said:

Now we can use the thread cutting router jig to make our own table

Yep.  Or the mechanical parts of your own planer design.  Or... 

In the 40+ years I've been teaching the need for threaded wood is pretty rare.  One student bought his own wood tap and die so he could screw in the legs of his dining table.  His design unfortunately perished when the weather changed and the wide mitered top broke apart.  Good for a few photos, but never served as a functioning dining table. 
4D