Thread Mill

[jmm0422]

I am not understanding how the over cut works with thread cutting.

 

On a 1/4-20 thread I will countor the .201 hole. I will use the same .201 hole to run the thread mill off of. How much over cut should I use on this thread?

 

I am using a single point Micro100 TM-140.

 

Thanks

 

Jason

[Allan]

The Allowance (overcut) increases the Diameter so a value of .049" should be used

 

Allan

[DaveR]

So overcut is the thread desired thread depth?

[jmm0422]

That is what I was going by. If I take The major from the minor that should be a pretty good guess?

 

I am at .060 for this thread and about .003 or .004 in the controller.

 

With a M10 X 1.0 I have .05 in for overcut to make a good size thread.

 

My thought process was right maybe it is just my crappy machine.

 

Jason

[Guest]

As a rule of thumb on and internal hole I will threadmill the major diameter and on an external thread I will threadmill the minor diameter.

 

Doing it in this way mean no extra calculating, chain your geometry, set lead in/lead out and let 'er rip

[jmm0422]

I tried that and ended up with about .025 overcut.

[Guest]

If your overcut is zero a nd your comp is zero,

 

One of 2 things is wrong then,

 

Your tool definition diameter is incorrect or your geometry for the major diameter is wrong.

[jmm0422]

I tend to think that it is machine error. I have my tools drawn and defined right on the money in MasterCam. I am going to be getting a new machining center in her end of the week. I will be doing some testing when it gets in.

 

Thanks

 

Jason