Straight-in threading question

[10XSHOOTER]

Turn your tool upside down and thread away from your shoulder. Got to have a machine that has a reverse for the spindle. straight in threading!

 

[LVLAaron]

Unless you have to thread at a high rpm, I find that method more trouble than it's worth.

 

[xr650rRider]

Unless you have to thread at a high rpm, I find that method more trouble than it's worth.

Because you can thread at high RPM totally makes it worth it. I've yet to find a downside to it. You wouldn't have crashed your lathe doing a blind internal threaded hole.

 

[LVLAaron]

I'll give you that, for an internal thread it makes a lot of sense.

 

[shutinlead]

A. Weldy,
This is coming from the peanut section that cuts quite a few miles of threads each year - for a living, not tool joints anymore but mostly stud style bolts for large gear boxes and cam frames- I do a straight plunge, on a 2.5" to 4" diameter 4 thread per inch, that's nearly .350" double depth of thread running about 350 rpm spindle speed so the thread dial has quite a rotational speed. Speed and rigidity are critical cutting this way. If you are still threading at 50 rpm on a 3/4" diameter and your setup's rigidity is shaky at best but looking for a good finish, use HSS tool bits, sulphur based cutting fluid and feed in with your compound set at 29°. Here's this afternoon's production in between customer calls and rests - I'm getting old... Yes, it's a manual machine, I have CNC's but the hastle to do a short run of 8 to 10 bolts for anything over 2-1/4" diameter and 24" long isn't worth the effort.
Greg

 

[jackieschmidt]

A. Weldy,
This is coming from the peanut section that cuts quite a few miles of threads each year - for a living, not tool joints anymore but mostly stud style bolts for large gear boxes and cam frames- I do a straight plunge, on a 2.5" to 4" diameter 4 thread per inch, that's nearly .350" double depth of thread running about 350 rpm spindle speed so the thread dial has quite a rotational speed. Speed and rigidity are critical cutting this way. If you are still threading at 50 rpm on a 3/4" diameter and your setup's rigidity is shaky at best but looking for a good finish, use HSS tool bits, sulphur based cutting fluid and feed in with your compound set at 29°. Here's this afternoon's production in between customer calls and rests - I'm getting old... Yes, it's a manual machine, I have CNC's but the hastle to do a short run of 8 to 10 bolts for anything over 2-1/4" diameter and 24" long isn't worth the effort.
Greg

We cut a bunch of threads as well, mostly the propeller nut thread on prop shafts. They range from 3 3/4 to 6 inch, almost all 4tpi.

We also make the nuts. We have a 24 inch Kingston lathe that is just about dedicated to boring and threading nuts. We don’t even use specialized threading inserts for the nuts. We just us regular triangle inserts with a .030 radius on the nose. Lots of RPM, 250 for a 5 inch.

The reason we make these is the ones you buy are just junk, all made in China.

these are 5 3/4

 

[shutinlead]

"We don’t even use specialized threading inserts for the nuts. We just us regular triangle inserts with a .030 radius on the nose. Lots of RPM, 250 for a 5 inch."

That's what I use - Sandvik TNMG 432. Up to 4.5 thread I lean towards the Kennametal top notch #4's in the TL3 and HL's when we can find them, I'm thrifty so eBay is my friend.

 

[Lucky Shooter]

Thanks again for all the replies.

I'm not going to ignore all this good advice. I'm doing a good barrel
for a BAT action and don't want to mess it up.

A. Weldy

 

[Scott-ak]

You MUST back out the tool before reversing! Why? the backlash in the system will ruin your threads and maybe your tooling.

A method that I didn't see mentioned, use and internal tool on the backside of the work and thread away from the chuck. It's simple and quick to learn