Cutting Threads?

[Bill Blasic]

If you do the female thread first make the Males size .070 bigger, female hole without threads 1" Male size without threads 1.070. I use the Baxter Treading Jig and cut the threads .035 on a side,

[Ken Schleman]

Thanks a lot for the help guys, I’ll try my first set tomorrow.

[Reed Gray]

Jeff,
I had a show in Davis, CA years ago on Mother's Day Weekend. Bunch of Mountain Mahogany boxes ready. Went down there from here in cool Western Oregon. Only the larger ones moved enough to feel the threads get tight when I turned the tops off. Had another one at a show locally that fell off onto the ground behind the table. Found it when I was tearing down the booth. It was maybe 1 1/2 inch diameter. I could get the lid off, but it was tight, and it never went back to perfect fit. It was myrtle wood. With friction fit lids, I have gone to 6 inch diameter. As long as I make the whole box from one piece, it seems to work even though I can't rotate them all the way around some times...

robo hippy

[John K Jordan]

Thanks a lot for the help guys, I’ll try my first set tomorrow.

Ken, you probably have plenty of advice by now. I didn't get to read all the messages.

I checked my notes and it looks like for 16tpi I cut the threads .043" deep. This left plenty of flat on the top of each thread, important in wood compared to metals.

I cut the lid first then the base but I don't think it matters if the calculations are correct - I made careful drawings before turning anything. The tenon for the base was then the inside diameter of the lid threads to the flats plus 2 times the depth of the cut minus 2 times the desired clearance. (I used .01)

As per Raffan, I shaped the box to nearly the finial dimensions then let it sit at least overnight to relieve any stresses that were in the wood. (This was, of course, after the box blank is completely dry.) I had good success with no chipping threading hard, fine grained woods - ebony is my favorite so far. Given the choice, I'd pick a blank from a part of the tree far from the pith since it is likely to be more stable with seasonal changes.

I was fortunate to have the luxury to set the jig up on a second lathe so it wasn't in my way and I didn't have to touch anything if I wanted to put the piece back on the first lathe for a minor tweak. (Which I did several times on my first little box!)

BTW, these are my first, third, and second attempts at threading using the Baxter jig, Black & White Ebony, no finish. Just for fun I made the one on the right a little "backwards" from usual with the outside threads on the lid and internal threads on the base. This lets the lid look smaller.

threaded_ebony_3_IMG_6755.jpg

A funny thing - when showing these to non-turners I was asked twice where I found plastic lids like that.

If you are interested, I found some good resources in books on my shop shelf including at least one book entirely on threading. I think one of Darlow's books was helpful too - I can look if you want. When I started threading I wanted to understand what was going on so I read everything I could find, made diagrams, and did the math.

JKJ