Ideas Needed Lathe Threading Lead help G76

[Buckshott00]

Hello,

I am having some issues, I am running a Mori Seiki SL25 lathe(Fanuc), and I was using a G76 Threading cycle to cut some id groove threads. I recently switched inserts and have been able to get much better chips. However, on a part that I just ran today. I adjusted only the depth of cut, and the lead of the thread is off to its qualifying point. I have no idea why, it shouldn't have affected it, so why is it out 0.010"?

Any ideas are appreciated

 

[BillPSU]

When you say the lead is out by .010 are you saying the thread position has shifted to some starting point on the Z axis. If that is the case then the insert is longer or shorter in the Z direction by the amount it shifted. Simply change the Z offset on the tool to correct the change in insert position.

If that is not the problem but he actual lead of the thread appears to be bad then the clearance from the cutting edge is not clearing the angle of the thread. You may have to increase the clearance angle on the insert if you are experiencing this type of problem.

Bill

 

[mfgenggear]

Buck

I not sure of your question?

is the thread Pitch Dia out of concentricity by .010" & what is datum on the part?
is the programming in Diameter or radius.
where is you zero point?
it is out x or z?
make sure the insert is seated properly.
do you print out your code. incase like this, so you can change it back.

Mfgenggear

 

[mfgenggear]

is this a multiple lead thread?
Is the pitch diameter unders size.

Mfgenggear

 

[berkshire]

Did you requalify the tool before you started?
B.E.

The good engineer does not need to memorize every formula; he just needs to know where he can find them when he needs them. Old professor

 

[Buckshott00]

Hello All,

It is a double start ballgroove thread.

When measuring it is out in the Z-axis. When I say it is out, I mean that from the qualifying point on the thread to the datum is out of position, when we measure the leads they are now out. I thought at first this was due to increased chatter with the deeper depth of cut. That it was actually a measuring issue instead of a cutting issue; however, that does not appear to be the case.

When I changed the program back to its original canned cycle it worked fine.

The insert is seated properly and touched off properly. The part is fixtured well and rigid.

I think I will check the clearance angle tomorrow.