Threading on the Lathe - Which TPI?

[Jason28]

What TPI would be best suited to turnings? I've got the option of 4, 10, or 16 tpi. I'm thinking either 4 or 10. Thoughts?

[SceneryMaker]

Is this a metal lathe where you can cut threads with a powered feed at these threads per inch or are you talking about the thread between the spindle and the chuck?

[Arlin Eastman]

SceneryMaker said:

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Is this a metal lathe where you can cut threads with a powered feed at these threads per inch or are you talking about the thread between the spindle and the chuck?

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Also are you talking about threading wood? If it is wood then go 16 and 12 is good too which are not to course nor to fine to chip.

Arlin

[Jason28]

Wow. I just re-read my post and realized how vague my question was. It's a wood lathe and in looking at getting a threading tool for threading wood. I'm thinking 16tpi might be too fine and 4tpi might be too coarse. 10tpi sounds like a good compromise. Thoughts?

[MichaelMouse]

Finer threads require denser woods to keep from crushing or chipping. Ten is as fine as I'd go for domestics.

https://www.toolsforworkingwood.com/prod...THRDCH.pdf

[iclark]

Lee Valley has a Thread Master on their clearance sale that started this afternoon. You buy the base unit and then the threading parts you buy to match your lathe spindle and your desired thread pitch to cut. The last time that I looked the 10tpi was sold out for the 1-1/4"x8 spindles but they still had that thread for some of the other spindle sizes.

The extra cutters and the extra 90mm cutter shaft sold out between the time that I put them in my cart and the time that I checked out.

Anyone know of another source for replacement cutters for the Thread Master?

[AHill]

Jason28 said:

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Wow. I just re-read my post and realized how vague my question was. It's a wood lathe and in looking at getting a threading tool for threading wood. I'm thinking 16tpi might be too fine and 4tpi might be too coarse. 10tpi sounds like a good compromise. Thoughts?

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Still confused. Are you waiting to cut threads for boxes or make screws?

[robo hippy]

For most boxes, they have to be small, like no more than 1 to 1 1/4 inch diameter at the threads because of wood movement. I went from humid Oregon to much drier Sacramento for a show, and I could still get the lids off, but it was a struggle, and yes, I rough turned them before I final turned them.

Now, for the mechanical cutters, I have an old Bonnie Klein jig and it takes a 3/4 by 60 degrees cutter, which is a fairly standard cutting tool, but don't know where to buy. If nothing else, the other threading jig makers probably have them. They are fine for cutting most woods, though softer woods will want to tear or break. Reinforcing the threads with softer woods can be done with find CA glue, but I usually lube the last few cuts with oil or wax which makes it cut cleaner.

I prefer the 16 tpi cutters for one simple reason. You need to line up the grain in the box, unless you are using 2 different types and colors of wood. You adjust by taking down the shoulder of the male part of the box, which is usually the bottom. So, at most you have to take off almost 1/16 of an inch to get the extra rotation needed to line things up. I do this with a negative rake scraper, and the last tiny bit can be done with the lid on 400 grit abrasive. If you have to take off more than 1/16 inch, you may have to recut the threads.

robo hippy

[Jason28]

For wooden boxes.

[hairy]

Many folks glue a piece of boxwood on each piece, and thread the boxwood. It is expensive wood.