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Turn groove surface finish

dion328

Plastic
Joined
Jan 8, 2024
Hi Machinist, I’m having trouble getting a good finish groove turning. I am working on a 4 axis turret cnc lathe (single spindle). The parts I do are often less than 0.625 inch, and is often smaller diameter in the back than front, with features on the front. I use a wida 1 inch parting tool to make the groove and part off. My feeds and speeds are 0.003 450 for (grooving) and 0.002 250 for finishing (grove turning). Is there a better tool for this? I would use a Turing tool facing the other way but that would mean putting my bar out further causing chatter.

Thanks!
 

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You're slowing down the spindle speed on your finish pass? Have you tried keeping it the same or speeding it up a bit?
 
What material. And which area of the part are you talking about the finishers all look pretty ordinary. If you mean the area in the corner then back turn it. Worried about overhang use a centre
 
I really like Seco MDT's for stuff like this. Its a good profile/cutoff hybrid, but its still blunt. My other thought is to use the cut off for roughing and cut off and use a sharp ground tool for a finisher. Your problem is turning a diameter with a straight cutoff, that's not really a great practice if your after a finish.
 
What material. And which area of the part are you talking about the finishers all look pretty ordinary. If you mean the area in the corner then back turn it. Worried about overhang use a centre
It’s hot rolled 1018, yes I was talking about the area in the corner. I haven’t tried back turning it and using a Center, might give it a shot

Thanks!
 
I really like Seco MDT's for stuff like this. It’s a good profile/cutoff hybrid, but it’s still blunt. My other thought is to use the cut off for roughing and cut off and use a sharp ground tool for a finisher. Your problem is turning a diameter with a straight cutoff, that's not really a great practice if your after a finish.
Yea I guess there not much a part off tool can do in terms of finish, was wondering if there were a low profile Turing tool so I can back turn while being close to the chuck

Thanks!
 
I was thinking:
Perhaps you could do nice job on the small end bevel, then come in with a femail center to center on that bevel, then take a last skim with a little larger nose radius bit/insert.
Or turn the part around and put the female center on the big end corner radius.

Seeing that you have no chatter a bigger radius could likely be tolerated..
 
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I would use a Kennametal A4 double ended grooving insert for this job. Reason being the cutting face of the insert is not dead flat but rather has a slight relief in the center of the groove. This type of insert is not suited for machining narrow grooves as the bottom of the groove will not be flat. However, they work awesome on wide turning style grooves (over 2x the insert width) because the center of the insert is relieved and prevents chatter.
 

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It's 1018 so you have to crank up the spindle speed like nerdlinger suggested, at that diameter your lathe might not spin fast enough.
 
I'll also add that sfm above 750 will help finish in 1018. In the absence of getting speed because of diameter limitation, use an insert grade/chipbreaker made for aluminum (i.e. sharper edge). You'll suffer some on tool life, but it should help your finish.
 








 
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