[stuby]

Hey guys Im working on a 4 foot long HRS Shaft right now that needs to be threaded on one end with an M36 X 4.0 Thread thats around 380 MM long ~15 Inches. Im using a Kennametal Top Notch Threading Insert, Carbide Grade K68 Uncoated. I seem to be having probems making the cutter last, it just doesn't hold up. Current Feed is obviously 4.0 and Speed is at 175, seems a bit fast, but as it is it takes me nearly an hour and a half to cut the thing, and Im barely making shop rate at this speed. Or does this thread just take that long to make? Its somewhere around 50 passes gradually taking a smaller cut as I get deeper into the thread, obviously. Any help with Speed or possibly using different inserts? Thanks a lot Guys, I appreciate the help ahead of time.

[fizzissist]

Am I correct that you're running 175rpm at about 1.4" diameter? That's about 65sfm.

I'm not familiar with the Kennametals, but I'd consider a coated insert and increasing the sfm up to 130, with deeper cuts. I'd also consider adding roughing tool, and just accepting that you're removing a lot of material and inserts are the price.

Sandvik looks like their GC1125 insert is in the ballpark, so whatever the Kennametal equivalent is....

"Reading" the insert at the end of the cycle should tell volumes about how it's wearing, and tell you if it's a problem with BUE, flank wear, cratering...or whatever, and make adjustments from there.

One problem I see is that you're really pushing the insert...ANY insert, with that long of a cutting cycle. You're cutting upside down for clearing chips? Either lots of coolant or none? (It's counter to my old mindset, but running dry often gives remarkable increases in insert life.....you're taking advantage of the heat...a lesson I still have trouble accepting) .. And if you're not getting chatter, push the insert as deep as you can get away with per pass. Let them flanks earn their keep.

Good luck!!

[Geof]

Another point is are you taking a skim off the OD to remove the layer of scale that is on HRS. It can be really rough on tools and when you are threading every pass exposes the insert to a cut in the scale.

[Thawk53]

As fizzissist said, more surface footage, put in a rough threading tool, and use a coated grade. If you want to stick with Kennametal, try KC5010 or KC5025.
What threading cycle are you using? 4mm pitch is a pretty heavy thread, and a threading cycle where you can adjust the infeed angle would probably help alot. If I were doing this thread, I would probably write a custom threading cycle with a modified infeed angle. Takes a little time and it's a lot of lines and characters, but I've found that a threading cycle like this works much better on the heavier threads than the canned machine cycles...

Edit: You are using a tailstock...aren't you?

Rick

[stuby]

Geof, the shaft has been turned down to correct size already, there is no scaling on the O.D. of my part, I figured I would just say HRS so you all know its just steel. I am most certainly using a tail stock, this part would be impossible to make without it, heh. And the suggestion for no coolant...hmmmm, that sounds a little strange to me, but I've heard even more strange and they seem to work most of the time, I guess Ill give it a shot. I have already purchased several new coated inserts this morning, hopefully it will work out a little bit better. I have always had issues making this part, as you said its a very long thread for any insert. As for the threading cycle, Im just using a standard cycle, Im pretty sure im using G92. I have heard about modifying the infeed angle before, but I have no clue what so ever as to how to do it, or exactly what it changes. Im 23, and basically learning how to lathe and CNC at the same time lol, the learning curve is PRETTY steep hah. Ill try out some of these suggestions though, thanks again for the help.

[fizzissist]

Geof, the shaft has been turned down to correct size already, there is no scaling on the O.D. of my part, I figured I would just say HRS so you all know its just steel. I am most certainly using a tail stock, this part would be impossible to make without it, heh. And the suggestion for no coolant...hmmmm, that sounds a little strange to me, but I've heard even more strange and they seem to work most of the time, I guess Ill give it a shot. I have already purchased several new coated inserts this morning, hopefully it will work out a little bit better. I have always had issues making this part, as you said its a very long thread for any insert. As for the threading cycle, Im just using a standard cycle, Im pretty sure im using G92. I have heard about modifying the infeed angle before, but I have no clue what so ever as to how to do it, or exactly what it changes. Im 23, and basically learning how to lathe and CNC at the same time lol, the learning curve is PRETTY steep hah. Ill try out some of these suggestions though, thanks again for the help.

Before you just throw money at it.....

While factory reps are notorious for making claims about their product's productivity, and just how fast they can remove how much material and their inserts last through next February.......Something to SERIOUSLY consider. Something really cheap, and lasts as long as a phone call.

Call your local Kennametal rep and ask for factory advice. They're desperate to keep your business from going to the 'other side'. My experience is primarily with Sandvik because in my particular situation, it was advantageous. What I found was that generally 50% or more of their suggestions worked. The other 50%? I was out an insert or 2, and in some cases, they fronted the tools. Maybe they'd offer a trial insert or 3 to get you up and running? Especially if it's a repeat job, and especially if they know you're on a forum ..........

....Why? .... it's read by a LOT of people, and it's free advertising if you rave about how well their product worked....... Just like I've raved about Sandvik (not all of their products, mind you) and Dataflute, and Emuge.

A 10 minute phone call to tech support at Emuge took me through an entire batch of parts ... 72 blind 0-80 holes in 304 SS on one tap... with confidence of not having to salvage some VERY expensive parts as I had in the past.

Remember too, what you hear on this forum is worth exactly what you paid for it...nuthin'. None of us can see your specific application, so we're just throwing our experience at what you're telling us. Could be something critical we're not seeing.

Keep us up on how it's progressing.

[Thawk53]

stuby,
What control are you using? Maybe we can come up with a machine canned cycle that will allow you to modify the infeed angle to see if that helps any. It would only be a couple lines of program.

Rick