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View Full Version : what up with the parting?



balsaman
06-03-2004, 10:55 PM
Well I have these "t" shaped parting tools. Seems great as the T shape provides relief below the cutting edge so that should help. Problem is the deeper you go the tighter things get, since there is no relief on the sides of the tool. Stalled my lathe. had to pry the tool out of the groove.

I have a parting tool that accepts the carbide inserts which will provide relief both below the cutting edge and on the sides. Is that the answer? I have not used it yet because I need to modify it to fit my tool post.

If that is the answer, why are these others available? Just to cut tubing?

Eric

Ken_Shea
06-04-2004, 12:07 AM
Balsaman what you need to do is take a cut as deep as seems workable then back it out move over a bit ( not a lot .005-.010)and make a new cut, cut again to a workable depth, back out and do it again in the same path as the first cut, this provides side relief for chips and tool expansion as it gets hot.

Ken

balsaman
06-04-2004, 07:17 AM
Ahh. That would do it.

Thanks.

kong
06-04-2004, 07:50 AM
I am no expert, but plenty of flood coolant should help too. I have used the standard blade type parting tools with no problems, and have just bought one of these: http://www.ishop.co.uk/ishop/728/shopscr23.html specially designed 12mm shank, to fit our mini lathes nicely. Price is steep, and the inserts are expensive, but should do a good job. Do you have a coolant setup yet?

HuFlungDung
06-04-2004, 11:17 AM
I'd agree with Kong, you should use coolant if at all possible.

HSS partoff blades are "almost useless" when parting off steel. This is because the chip does not get "smooth" until the circumferential speed is above...I dunno..... 300 feet per minute. Since HSS can only stand 100 feet per minute (or less in steel cutting) this presents a bit of a problem.

There are often tool company promotions where they will sell you 10 carbide inserts and give you the blade for free. This might be something to ask about. However, you will have to have your own blade holder, and the typical Armstrong style partoff blade holder might have to be replaced with a new unit designed for carbide insert blades.

Even though carbides should also be flooded for parting, I do use them dry a fair amount of the time in manual machining. You've got to "think positive" and really feed the tool in though. The aim is to make a nice "clockspring chip coil". Stop the cut once in a while, back the tool out and apply some cutting oil to the cut (you'll want to ventilate the fumes). Don't crack your carbide by using little shots of watery coolant. Flood is okay, but now you know why we have a coolant window in a sliding door on the lathe :D