Internal Threading Speed Recommendation

[dgoddard]

Threading Speed Recommendation?

--------------------------------------------------------------------------------
Looks like I posted in wrong area (Metalworking Machines) so reposting here.


I'm about to do my first internal threading operation. The thread is a 1-5/8" - 16 tpi. From way steel machined on turning and boring figure it is probably in the Brineel hardness range of 175-225. My lathe is a converted Grizzly 0602 (10x22). Using Mach3 wizzard for G-code. On smaller dia stock I used 500 rpm for external threading. With the larger dia and my first attempt at internal, thought would ask for some recommendations from those who have been there, done that.

Merry Christmas

Opps, left out that will be using laydown indexable A60 carbide insert on 3/8" bar.

[tobyaxis]

Originally Posted by dgoddard Threading Speed Recommendation? -------------------------------------------------------------------------------- Looks like I posted in wrong area (Metalworking Machines) so reposting here. I'm about to do my first internal threading operation. The thread is a 1-5/8" - 16 tpi. From way steel machined on turning and boring figure it is probably in the Brineel hardness range of 175-225. My lathe is a converted Grizzly 0602 (10x22). Using Mach3 wizzard for G-code. On smaller dia stock I used 500 rpm for external threading. With the larger dia and my first attempt at internal, thought would ask for some recommendations from those who have been there, done that. Merry Christmas Opps, left out that will be using laydown indexable A60 carbide insert on 3/8" bar.

First thing first, if you have a larger Threading Bar, (1/2, 5/8,3/4 Dia) use it.

Second, it is always best to start with Low Feeds and Speeds when attempting something for the first time.

Third, try to use a good cutting oil, not coolant.

How well are you holding the part, and what size chuck?? I am not a Grizzly Lathe user, LOL.

[BobWarfield]

Doug, the feedrate is, of course, determined by the thread. So, you want to basically select the SFM that is appropriate, and the feedrate will then be a function of how fast the tool must move to cut the appropriate helix that is your thread. I am assuming you CNC software will deal with figuring the feedrate for the thread at some level.

So, start with what SFM is recommended for single point turning with a carbide insert in the material you have. I wouldn't be averse to being a little lower than that SFM, but if you go too terribly low, sometimes the carbide doesn't cut very well and can tear your material. As a rought guess, I would go no lower than 50% of the recommended SFM. If you can do a test pass on the material, that is really helpful in determining the best cutting conditions.

Cheers,

BW

PS Guess I'd better get a hardness table into G-Wizard, eh?

[dgoddard]

Thanks Bob. You confirmed my thoughts and will go that route. Thought about doing a test piece but as Murphy goes I have the piece already setup from the boring op and want to keep it centennial to the center. Adding hardness would be good. Like what you've done with G-Wizzard thus far.