Sloppy threads

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NJturner

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New Jersey, USA.
I recently finished all my normal turning for holiday gifts and am getting back to my penmaking. Doing the first drilling operations quickly got me to the point where I knew I needed to realign my wood lathe. I broke everything down and re-set headstock/tailstock alignment and I am happy. I proceeded to drill, cut the tenon on the section and do the threads for the body and section. All good. I tested the section threads into the body and am not super happy. Despite everything being aligned on the lathe and my Hinze tenon cutter being correctly set, the Alumilite section doesn't fit super well into the Alumilite body. It is loose on the initial threading down, with what I think is an unreasonable amount of wobble, but it does lock down tight to the body once fully threaded down. Threads are clean and sharp both in the body and on the tenon.

I am unsure of what is going on here, but am thinking I need to adjust the die opening a bit using the screw in the die. I have the Tapco 10mm die set bought in the group buy here - it is in good shape and well treated, but I have never adjusted the screw in the die. Has anyone had this issue and did any adjustments to the die sizing?

Appreciate your thoughts!
 
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Just a thought.

Take a look at your die holder. I had a particular problem with the Neils die holder that I was using when I started. Depending on the length of your tenon, what I found is that the tenon of my section was a bit longer than the length of my die. What was happening was that the end of the tenon was exiting the die and reaching the small shaft of the die holder, and as I added more threads, the small shaft opening was slightly crushing my starting threads. This led to what you are explaining; my threads would start loose and get better as I went up the tenon. It took me weeks to figure out why my sections were loose at the first threads.

At first, I had to make my tenons uncomfortably short to fit, but then I switched to Rick Herrels' die holder, which has a much larger shaft and allowed my tenon to pass through without touching the inside shaft of the die holder.
 
As far as adjusting the die, the more you screw out the adjustment screw, the tighter the die gets. So you would be cutting deeper threads. If you screw in the adjustment screw, you are widening the die, thus making shallower threads.

I don't know that I would mess with it that much, if your threads are tight at the back end of the tenon.
 
hooked said:
Just a thought.

Take a look at your die holder. I had a particular problem with the Neils die holder that I was using when I started. Depending on the length of your tenon, what I found is that the tenon of my section was a bit longer than the length of my die. What was happening was that the end of the tenon was exiting the die and reaching the small shaft of the die holder, and as I added more threads, the small shaft opening was slightly crushing my starting threads. This led to what you are explaining; my threads would start loose and get better as I went up the tenon. It took me weeks to figure out why my sections were loose at the first threads.

At first, I had to make my tenons uncomfortably short to fit, but then I switched to Rick Herrels' die holder, which has a much larger shaft and allowed my tenon to pass through without touching the inside shaft of the die holder.
Click to expand...
This sounded like the perfect possibility to me - but, alas when I measured, my M10x1.0 die is deeper than my tenon - not by much, but it is. I do a 5/16" tenon which comes out to 8.02 mm and my die is 9.62 deep, so open and not crushing things. But I have to say, I ran down to my shop and did some measurements, because this sounded like it! Thanks!

Kevin
 
I would double check the hole in the cap. If the drilled hole is slightly bigger than the called for minor diameter you can get the slight wobble you described.
 
Just a thought.... Do you cut a relief in the ID of the barrel tenon once you have cut the internal threads? If you cut too deep of a relief (I usually us a "K" bit and a 3mm relief), the starting threads could be sloppy until they engage the actual 10mm internal threads.
 
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