My Wood-threading adventure

[Dan_Shade]

I have been working on making wood threads and nuts, I have had a few false starts, but I've learned a few things, and certainly still have plenty of room to learn more.

I had a false start when I thought I could make them with a jig to reduce the rotational rate with a 3/4-6 acme thread to turn and advance a blank, and I used the table saw t-track and fence to hold the jig and router.  this almost worked, but the centers have to be aligned, or the blank will be tapered.  My test piece was 1/16" off in diameter from end to end, which was pretty sloppy when I made a temporary female thread test peice with bondo.



 

 


the bondo "nut"  I waxed the wood threads, drilled a hole slightly bigger than the Major Diameter of the thread, sawed the blank in half, and sandwiched Bondo into it.



 

I rigged up a cutter to add to the threaded piece.  I got fancy, and made it open, so that it would cut with a knife edge rather than a scraping action.  I don't think this really worked.  it ended up deforming the tap where I had it mortised, and eventually the screw cracked.



 

 

 

 

As you can see it "worked", but the tap broke.  So I went back to the drawing board.

I found an article on "The Woodwright's Shop" website titled Carpenter's Tap.  I regrouped and made a new tap:


 
First step is to mark off spacing for the thread pitch, in this case a division every half inch:

 Next, I used the indexing stops on the lathe to make a parallel line down the length of the "tap" every 60°, resulting in six lines. 

The next step is to determine how to start the spiral of the thread.  My spacing is a half inch, and I have 6 divisions (360°/6=60°), so I needed to divide the 1/2" by 6 which is 1/12".  I have a framing square that has a 1/12 rule on it. 

So, rotating the tap 60°, a mark 1/12" from the 0 reference, and so on until the tap has rotated 360°.




 2/12 marks

 3/12 marks

 and so on...

 

 connect the dots with a flexible straight edge

 

 

 

[Dan_Shade]

Saw around the blank to about 3/16 depth:

 

I then made a "snail":



 

 

 

Then I created this contraption to drag the cutter/scraper through the nut blank:



 



 

 

 


Video of cutting threads:

Cutting wooden threads - YouTube

[Dan_Shade]

making the screw:

I used a "nut" that was tapped and set the router on it to cut the threads.  this is very finicky.  it took me a while to figure it out.  the one I did with 60 degree threads worked on the first attempt (dumb luck).  

if the router is not in the correct location, the threads will either bunch up or be too far apart.  If they are too close together, you need to move the bit away from the nut; if they are too far, the router needs to be closer.



 
 

 

 



 

 

[low_48]

Quite the adventure Dan. I think you'll like what my friend is doing with wood threading. His double threaded pedestals usually have a gear train in the table to let a single crank or wheel, spin two threaded shafts to elevate the table top. All his work is made from all wood, no metal, no salvage or recycled components. He travels the high end art show circuit, all over the US.   http://pearcepearce.com

[Dan_Shade]

That's really interesting.  Very unique. 

I'm not quite to that point yet.   ;D

[trimguy]

I find that very interesting. Good job. Thanks for posting.

[Weekend_Sawyer]

That's really cool Dan!

[Dan_Shade]

Thanks. 

I modified the original posts to add details on how to establish the spiral. 

[21incher]

That's a great jig 8). I took the easy way out and bought a Beall. 

[Dan_Shade]

2-1/4" OD 2 threads per inch. 



 

[kantuckid]

Impressive work indeed.