Best cutoff tool profile?

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Greg_Lewis
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Best cutoff tool profile?

Post by Greg_Lewis »

Hi folks:
I need a 1/16 cutoff blade. Which profile do you like and why? Taper or T-shape?

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Bill Shields
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Re: Best cutoff tool profile?

Post by Bill Shields »

T
Too many things going on to bother listing them.
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Greg_Lewis
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Re: Best cutoff tool profile?

Post by Greg_Lewis »

Bill Shields wrote: Sun Dec 04, 2022 10:07 pmT
Because.....
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Bill Shields
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Re: Best cutoff tool profile?

Post by Bill Shields »

It is what I have been using for 50 years and see no reason to change from something that works for me.

Old dogs / new tricks.
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Greg_Lewis
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Re: Best cutoff tool profile?

Post by Greg_Lewis »

Bill Shields wrote: Sun Dec 04, 2022 10:34 pm It is what I have been using for 50 years and see no reason to change from something that works for me.

Old dogs / new tricks.

As they say, if it works, don't fix it.
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Bill Shields
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Re: Best cutoff tool profile?

Post by Bill Shields »

Thinking about it...I started with a T.

Over the years, as I got involved with CNC programming and software development, I became aware that the majority of the replaceable cut off inserts are T shaped, or very close to that.

If I were going to use a cutoff for other than straight parting...then yes, the other profile may have attractions
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Greg_Lewis
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Re: Best cutoff tool profile?

Post by Greg_Lewis »

I should have mentioned that I'm buying plain vanilla HSS.
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Bill Shields
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Re: Best cutoff tool profile?

Post by Bill Shields »

Is what I use at home.

Despite what I program and develop software to use...I am still a chicken at heart when parting.

I have my numbers for speed and feed that work for each lathe and stay with it.

Machine rigidity plays a big part of it.

My Asian lathe does not part off nearly as well as either of my south bend units....which I am positive has to to with cross slide and compound rigidity.
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Greg_Lewis
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Re: Best cutoff tool profile?

Post by Greg_Lewis »

Hi Bill:
Yes, rigidity counts for a lot. If you've followed my posts over the years you might remember that my lathe is an Atlas/Craftsman 12, which I have dubbed "the flexible flyer." Even though it's on a metal stand made from heavy welded angle iron and 1/2 inch plate top, I can put a DTI in the toolpost and its tip against the chuck and watch the dial move when I push on the headstock. I have determined that it will chatter depending on the alignment of the planets and phase of the moon.

Years ago I met a man over in Carson City who owned a business making parts for rockets. His personal home machine shop would have put a number of commercial ones to shame. In about five minutes I learned more about toolbits from him than in all the books I'd read up until then. And what I came away with is that HSS is the best choice for my flexible flyer. So far he's been right. Not too long ago someone suggested I get a carbide spotting drill. I didn't remember my five minute lesson and bought the carbide. $30 bucks and it didn't last one use. Anyone need a stub of 3/8 round carbide? Blah blah blah — back on topic: Sometimes I think parting off is best done with a hacksaw!
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Our motto: "That looks about right."
Celebrating 35 years of turning perfectly good metal into bits of useless scrap.
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liveaboard
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Re: Best cutoff tool profile?

Post by liveaboard »

My lathe is also rigidity challenged... No, not Asian, just small size and old.

I've struggled with parting too, and finally had some success after trying many grinds on my HSS blade.
Basically; sharp, correct height, slightly V, and as close to the headstock as possible.

I'm not even sure what changed because I thought I did all those things before, when I had no success at all.
I think it was just my own slowly developing skill that passed some invisible point.
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rmac
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Re: Best cutoff tool profile?

Post by rmac »

It seems counterintuitive, but the biggest breakthrough for me when parting off was discovering that sometimes it helps to take a heavier cut to avoid chatter.
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Bill Shields
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Re: Best cutoff tool profile?

Post by Bill Shields »

Not counterintuitive at all.
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