Another single point threading question, sorry guys.

[Larry$]

I use the KISS approach. Sharp tool, forget the 29.999* stuff, plunge straight in, deburr when you get close and try a nut, or if you are going for interchangeable, use the one wire system and measure with the micrometer. Save the other two wires for when you loose one. I didn't invent any of this. It makes sense to me and best of all it works. I also don't like to thread toward the shoulder so run the tool upside down, which BTW allows me to run at higher speed. But you can't do that with a threaded chuck. Thank you Joe Pie.

 

[machPete99]

I made a drawbar recently, using 4140PH. I single point threaded it about 90% of the way, then used a die in a tailstock die holder to finish it up.
It came out pretty good, much better that the one that came with the mill.

The tailstock die holder was another project of its own, the guide part being made from an older MT shank reamer that I got for cheap.

 

[erikmannie]

I just used a Carbide insert threading tool yesterday to cut a 7/8-20tpi and now I'm absolutely hooked it's the only thing I will use anymore....

I quickly developed a strong preference for the carbide 60 degree form tool. Not that there is anything lacking in HSS!

 

[Shiseiji]

I have a Logan 820 10" lathe that obviously pre-dates carbide in a hobby shop, with a current max rpm of ~1400 with the non-stock pulleys it came with. Not really different than what stock gave. So far in my very limited attempts, I've used both carbide and HHS. I've had my best results with HHS, using all three techniques I've found in various places:

• The typical American technique with the compound at 29.9 degrees
• The English technique with the compound parallel to the bed and 90 degree plunge cut with occasional compound increases to relieve some of the right side pressure. This is the technique covered in the workshop series Screw Cutting on the Lathe.
• A 90 degree plunge cut.

I find I like the English technique. If everything is going well, it's a simple plunge. If I see some issues with the right side of the thread, I can play with the compound to clean it up.

I'm able to afford a set of AR Warner HHS indexed threading tooling to not add "must get a good grind" along with my other frustrations. I'm wound tight, and know it I like the HHS a I don't need the speed and pressure required for the best carbide work though I have had decent results with 1/4" carbide, not so much with 1/2".

Just my $.02 noob experience.

Ron

 

[e189552]

I understand that cut threads are never allowed on aircraft (as the sharp edge can act as a stress riser). Rather, all threads on an aircraft must be rolled, and, as such, never made in a home shop. I could be misinformed here.

Almost all threaded fasteners in aircraft are rolled threads. That being said, I have threaded thousands of parts by single point threading, on everything from C-5's to F-16's. Materials ranged from high strength steel to aluminum to titanium, both internal and external. Measured with the 3-wire method (external), checked with GO/NO-GO ring or plug gauges.

 

[Larry$]

An easy way to pick up an existing thread, particularly when doing metric on an imperial lead screw, set the compound parallel to the bed. You can then easily adjust the tool to match the existing thread just by moving the compound. Not that I've ever messed up and lost my position when metric threading. But I have used this technique to recover. Thank Joe Pie for it.

 

[Tozguy]

Easier still is to just loosen the tool in the holder and locate the point in the threads by hand. Then tighten the set screws while holding the point of the tool in the bottom of the thread.

 

[epanzella]

Easier still is to just loosen the tool in the holder and locate the point in the threads by hand. Then tighten the set screws while holding the point of the tool in the bottom of the thread.

^^^ That's the way I do it. Don't forget to to take out the endplay first. I just run the lathe in the direction of the thread and kill the power to take out the backlash.