Need Help!- M42 x 2 thread, first thread is sharp! Help...

[Driftwood]

Hey guys,

I'm threading some parts here and I'm under the gun to get this done today.

I've never layed down a thread like this and don't like the way its coming out.

So its a 42mm thread with 2mm pitch. All the complete threads look great, expect the first one.

Because it doesn't have complete material to form the full thread, its coming out sharp and there are burrs. I can't figure out how to overcome this.

Currently, where the thread starts, I put a 60 deg angle on the front wall that the thread enters on, hoping that the 60 deg thread will match up with that angle and leave less of a burr. Its helped a little, but still not great.

The thread op starts beyond the front of the part, then moves in.

Any tricks you guys know to get that first (partial) thread to come out nice and not too sharp?

FYI, the material is Nitronic 60, kinda like stainless 316. Using a single point lay down threading bar. SFPM = 360

Help!!

Edit: forgot to mention, its an OD thread...

[laka]

If it's on a CNC, you can program to clip the thread. Takes some practice and patience though.

What about just taking a file to them and touching them up by hand?

[Driftwood]

Its 150 parts, so trying to avoid that...

Finally settled on putting a 45 deg chamfer on the front, then threading, the running the finishing tool again, then one more spring pass with the threading tool.

Seems to be working pretty well., just needs a scratch from a file at the end...

What did you mean about clipping the thread? and how?

Thanks for the response, by the way...

[laka]

Basically you use a grooving tool in a threading cycle and adjust the tool offset so it's center is at the crest of the thread. Have your thread start in front of the workpiece, and have the thread end just as the actual thread you just cut begins.

If you do a quick search you should be able to find some better explanations on it. I'm more of a milling guy so I've never done it before, but have seen it done. The thread looks quite nice once you get it all adjusted properly.

[gsrmmeza]

Search for "Higbee"




I also found a post with a pic.


http://www.cnczone.com/forums/showpo...06&postcount=5

[manoharan]

Starting thread (first thread) make releif on 3/4 thread and if need cut hig bee. You know about releif thread and hig bee?

[Driftwood]

I saw the link for the hig bee, I'll give that a try next time...
Though I'm not sure I understand the code because my machine doesn't use G76 for threading... I get a new line for each threading pass using a G32 command i think...

And I don't know what you mean by "thread relief on 3/4 thread", can you explain?

[Geof]

Originally Posted by Driftwood .. I get a new line for each threading pass using a G32 command i think...

I think with G32 you should be able to program the Higbee cut. G32 lets you command a tool retraction (that is a X+ move) wherever you want. (Yes? No?)

[juergenwt]

150 part - asap?
Chamfer 45 deg. and use a file to flatten the start of the first thread.