Threading problem

[3strucking]

I am try to cut internal threads and they look like crap. I am using insert tooling. I made sure my tool was on center. I am attaching pics. Any help would be appreciated.

 

[T Bredehoft]

They don't "Look like crap" to me, They may not be deep enough, can't really tell, but they aren't torn at all, they are evenly spaced, Is your insert on the back of the work? is the lathe turning in reverse? Should be with the insert in back, can't really see it in your third picture.
The threads look OK.

 

[JimDawson]

From the pictures they look pretty good. What cutting oil were you using?

 

[Moper361]

I recon they look okay to its not easy to get picture perfect finnish when cutting threads on lathe thats my experience anyway

 

[3strucking]

they look too flat. I cut to .034 depth using the compound so I am probably around .030 thread depth. I am using a RH micro bar and inserts since thats all I have that will fit. The bar is mounted upside down and I am cutting on the back side of the work.

 

[T Bredehoft]

Keep going until there is a V on top of the thread. There's no telling (can't measure) the depth of an ID thread. Or, if you have a male thread that needs to go in there, take a light pass, check, keep doing this till it fits.

I just did some 5/16-24 threads, should be .041 deep, I went almost .050 deep on the dial and finished them with a die, took quite a bit of metal out with the die.

 

[Silverbullet]

The only way to tell is fit them to the male counterpart. They look ok but flat , yet I've seen lots of internal threads on other items the same way.

 

[3strucking]

They look too flat to me also. Spec calls for a .023-.032 thread depth and I was at .017 on my compound. I have not made the male part yet.

 

[higgite]

they look too flat. I cut to .034 depth using the compound so I am probably around .030 thread depth....

They look too flat to me also. Spec calls for a .023-.032 thread depth and I was at .017 on my compound. I have not made the male part yet.

The threads also look flat topped to me. Keep in mind that .017” on the compound will give you approximately .015” thread depth, not .030”. Depth of cut is what it is. No 1/2 diameter or 2 x radius calcs needed like turning to a specific diameter.

Tom

 

[hermetic]

What you need, and probably haven't got, is a factory made sample of the thread to try in the hole. That thread doesn't look bad actually, internals are that bit more difficult as you can't see as well, and chips tend to get stuck in the thread more and can damage it. Having said all that, I concur with the others in thinking that the tops still look a bit flat, and you need to go a bit deeper with the thread. When I get to this point, I try a male thread in the hole, and see if it will start, and if it will, I take a few more cuts on the same setting to take the spring out of the setup, and if the thread still won't fit smoothly, take another very small cut of about 1 to 2 thou. and try again. If you are worried about the wall thickness on the tube, make the other part, thread it, and proceed till the two just fit together smoothly. Hope this helps, Like much of engineering, the more you practice, the better you get!