Cutting Type A Point Wood Screw Threads

[Rustystud]

I would like some help on how to cut Type A wood screw threads on a lathe. I want to cut them on 3/8 hot roll rod. I know they are comercially cut with a threading head. I was told the threading dies would cost $5,000 for this particular thread type. If these threads can be cut with a single point tooling. My first question is do I cut the taper first then cut the threads. Or do I cut the threads with a taper attachment and multiple passes. The lagg screws look as if a acme type tool bit is being used. They look to be 5-6 threads per inch pitch. The Machinest Handbook was not much help. I want the threaded portion of the rod to be about 2 inches in length. I believe hot roll will work best because it will be less brittle. Your ideas and recomendations are welcomed.
Thanks
Rustystud

[John Stevenson]

Rusty,
Hot rolled threads like crap, draggy and stringy.
Leaded steel threads the best if the material is suitable.
I have never done a wood screw but have done many tapered tails like what you screw buffing wheels onto.

I turn the taper with the tapering attachment then single point it so the threading tool which is the most fragile is only removing the minimum amount.

One thing I have noticed is that if you place the tool square to the taper then although the thread should be right it looks drunken as it relates to the taper.
I have found that if you lead the tool towards the larger end although not correct the thread definitly look better.
Perhaps it's an optical illusion, more likely it's because I'm blind................

John S.

[Rustystud]

Thanks John:

The books all say to cut the threads at 29 1/2 degrees with a 60 degree tool bit moving 90 degrees towards the path being cut. I agree they look loopsided to me too.
These screws will be used in trees.
Rustystud

[John Stevenson]

Rusty,
What are these for?
The reason I ask is that we can buy what are called wood to metal screws here.
They are used for screwing into furniture and leave a metal thread sticking out.
Classis uses are the tops of table legs where the gusset of the top is held on with a wing nut.
3/8" x 2" is a popular one here.

Just thought it might save a bit.

John S.

[SGW]

Welll...in the early days of screw threads, they didn't have a tapered point. They were uniform diameter. That would simplify things a bit, and as long as you have a suitable pilot hole, the result ought to work.

[Ries]

John- what you in the UK call wood to metal screws are readily available here in the US as well- here we call them dowel hangers, and they have a standard machine screw thread on one end, and a lag screw thread on the other.
But I dont think they are what Rusty wants.

[wierdscience]

I have made those by cutting off lag screws and welding them onto the rods,works good so long as the weld is 100%.

I have cut wood screw threads,I used an acme threading tool and just calculated the pitch I needed so that 2/3 of the material was removed in one pass.

[Rustystud]

John:

These will be used as anchors for tree steps.
Later
Rustystud