Best cutoff tool profile?

Topics include, Machine Tools & Tooling, Precision Measuring, Materials and their Properties, Electrical discussions related to machine tools, setups, fixtures and jigs and other general discussion related to amateur machining.

Moderators: GlennW, Harold_V

User avatar
Greg_Lewis
Posts: 3014
Joined: Wed Jan 15, 2003 2:44 pm
Location: Fresno, CA

Re: Best cutoff tool profile?

Post by Greg_Lewis »

rmac wrote: Mon Dec 05, 2022 6:30 am 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.

The machine shop prof. at the university used to say that if you get chatter, try a slower speed and a faster feed. If Saturn is up and Mars is in Virgo, that works. Sometimes.
Greg Lewis, Prop.
Eyeball Engineering — Home of the dull toolbit.
Our motto: "That looks about right."
Celebrating 35 years of turning perfectly good metal into bits of useless scrap.
User avatar
Greg_Lewis
Posts: 3014
Joined: Wed Jan 15, 2003 2:44 pm
Location: Fresno, CA

Re: Best cutoff tool profile?

Post by Greg_Lewis »

By the way, I found this on the net:

2000-6010d92019.jpg
Greg Lewis, Prop.
Eyeball Engineering — Home of the dull toolbit.
Our motto: "That looks about right."
Celebrating 35 years of turning perfectly good metal into bits of useless scrap.
earlgo
Posts: 1795
Joined: Sat Jan 29, 2011 11:38 am
Location: NE Ohio

Re: Best cutoff tool profile?

Post by earlgo »

by Greg_Lewis » Mon Dec 05, 2022 12:01 am
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.
My 12" Atlas does the same thing in spite of tightening every bolt in the lathe and base, and the leg pads are glued to a cement floor. I have made sure the spindle bearings are tight. I have done what I can with the attachment of the drive pulley to the headstock gear, but there is still a bit of slop after 65 years. I don't understand how it flexes that much in such a short distance.
Chatter city if I don't have the speed set right. I have finally come up with a cutoff method that helps. I run the tool in about 2x the width, back out, move over 1/4 width, run the tool in about 2x the width deeper than the first, back out, move the tool to the original position, etc. until the parting is complete.
Oh and I agree with the HSS cutoff blade, and the one I use is tapered top to bottom.
--earlgo
Before you do anything, you must do something else first. - Washington's principle.
User avatar
Bill Shields
Posts: 10464
Joined: Fri Dec 21, 2007 4:57 am
Location: 39.367, -75.765
Contact:

Re: Best cutoff tool profile?

Post by Bill Shields »

Greg_Lewis wrote: Mon Dec 05, 2022 8:28 am By the way, I found this on the net:


2000-6010d92019.jpg
that appears to be what I used = T at the top, i don't care about the bottom....
Too many things going on to bother listing them.
User avatar
Greg_Lewis
Posts: 3014
Joined: Wed Jan 15, 2003 2:44 pm
Location: Fresno, CA

Re: Best cutoff tool profile?

Post by Greg_Lewis »

earlgo wrote: Mon Dec 05, 2022 10:12 am My 12" Atlas does the same thing in spite of tightening every bolt in the lathe and base, and the leg pads are glued to a cement floor....

Nice to know that I'm not the only one.
Greg Lewis, Prop.
Eyeball Engineering — Home of the dull toolbit.
Our motto: "That looks about right."
Celebrating 35 years of turning perfectly good metal into bits of useless scrap.
User avatar
tornitore45
Posts: 2077
Joined: Tue Apr 18, 2006 12:24 am
Location: USA Texas, Austin

Re: Best cutoff tool profile?

Post by tornitore45 »

Purchased parting tool: Use T a grind a longitudinal v or u grove on the top.
Home ground: T is impractical taper just enough. All is needed is to keep from rubbing the sides, too much taper and you have a weak tool.
Mauro Gaetano
in Austin TX
Rich_Carlstedt
Posts: 1754
Joined: Sat Dec 21, 2002 12:16 am
Location: Green Bay Wisconsin USA
Contact:

Re: Best cutoff tool profile?

Post by Rich_Carlstedt »

have to be careful fellows !
Lots of Chinese tooling out there that is wrong.
here is a few shots to show you bad, and good .
Enco sent me new "Good" tools aft I showed them the pics.
So last week I was at our Tech College---and guess what, they have the bad version of the tools
Rich
ENCO-New Blades A.jpg
Old Cutoff Blades A.jpg
User avatar
Greg_Lewis
Posts: 3014
Joined: Wed Jan 15, 2003 2:44 pm
Location: Fresno, CA

Re: Best cutoff tool profile?

Post by Greg_Lewis »

Interesting, Rich. I got burned by Enco (and some appalling treatment by the personnel) many years ago and didn't go back. I thought MSC bought them out and shut them down.
Greg Lewis, Prop.
Eyeball Engineering — Home of the dull toolbit.
Our motto: "That looks about right."
Celebrating 35 years of turning perfectly good metal into bits of useless scrap.
Rich_Carlstedt
Posts: 1754
Joined: Sat Dec 21, 2002 12:16 am
Location: Green Bay Wisconsin USA
Contact:

Re: Best cutoff tool profile?

Post by Rich_Carlstedt »

I posted this before on a Parting Tool Thread to help those who have
issues with parting. You also should look at Power feed when parting as most crashes occur when the handle is turned from
The one o'clock position to the four-five o'clock position due to sudden downward force ( uneven feed )
here is what can be done to help
Rich
Cutoff No No's #1.jpg
Cutoff No No's #2.jpg
Cutoff No No's #3.jpg
Cutoff No No's #4.jpg
Rich_Carlstedt
Posts: 1754
Joined: Sat Dec 21, 2002 12:16 am
Location: Green Bay Wisconsin USA
Contact:

Re: Best cutoff tool profile?

Post by Rich_Carlstedt »

Greg_Lewis wrote: Mon Dec 05, 2022 8:15 pm Interesting, Rich. I got burned by Enco (and some appalling treatment by the personnel) many years ago and didn't go back. I thought MSC bought them out and shut them down.
yes Greg, those straight sides are murder, they create heat and scuffing and yet still being used I guess.
Wonder if MSC has the inventory too ?
Rich
User avatar
Greg_Lewis
Posts: 3014
Joined: Wed Jan 15, 2003 2:44 pm
Location: Fresno, CA

Re: Best cutoff tool profile?

Post by Greg_Lewis »

AH HA! Excess overhang. Never thought about that. Something to pay attention to. Thanks, Rich.
Greg Lewis, Prop.
Eyeball Engineering — Home of the dull toolbit.
Our motto: "That looks about right."
Celebrating 35 years of turning perfectly good metal into bits of useless scrap.
User avatar
Bill Shields
Posts: 10464
Joined: Fri Dec 21, 2007 4:57 am
Location: 39.367, -75.765
Contact:

Re: Best cutoff tool profile?

Post by Bill Shields »

I actually have 4 cut off tool holders, each with a different width of blade, set at different hangouts so that I can just grab and go.

One I have with the tip ground non parallel to the centerline so that it cuts off and leaves minimal nub.

You can never have too many tool holders.

Amen on the oddball cross section shapes.

You can also get into trouble it you get the blade mounted non-vertical.

I lay the holder on its side, then put an adjustable parallel up under the small section of the T to get it square with the holder...

All this is assuming that the small section of the T is not tapered.
Too many things going on to bother listing them.
Post Reply