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Question about using parting tool

Kevin T

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Jan 26, 2019
I am working with a 2.0 Dia x 13" Long piece of steel and I want to cut off the end that I have been working on for further machining. It is supported with a live center. I looked online and couldn't see anyone parting a heavy piece so I am looking for some wisdom. I can rig up something to catch the part as I finish parting but figured I should ask before I attempt it.
 
Assuming your 13" piece of steel is hanging out most of that length, what you describe will not work! With the live center in place, something is going to go crunch when the parting tool finishes. Without the live center, the parting tool will chatter like crazy.

You need to either shorten the workpiece by sawing it shorter or burying it in the spindle bore, or support the far end with a steady rest.

Or better yet, saw it off with a bandsaw and finish the sawn end separately.

Regards.

Mike
 
Assuming your 13" piece of steel is hanging out most of that length, what you describe will not work! With the live center in place, something is going to go crunch when the parting tool finishes. Without the live center, the parting tool will chatter like crazy.

You need to either shorten the workpiece by sawing it shorter or burying it in the spindle bore, or support the far end with a steady rest.

Or better yet, saw it off with a bandsaw and finish the sawn end separately.

Regards.

Mike

That makes sense. I was hoping there was some old timers trick! I'll use the parting tool until I get chatter and then finish with a hacksaw..... or I might be able to flip the part around and use a steady rest.
 
Old time trick is to part a parting line held that way .015 .030 (about ) wider than your hack saw blade. If feeling good you might part it down to 1" dia.

Yes off the tail with the hack saw.

Or just the out-end held in the steady..with the off cut out hanging with a closed box to fall into.
 
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Parting off a piece of steel that diameter also has the possibility of running into an inclusion or klunker that will mess things up pretty well.Do you know what kind of steel it is.
 
Parting off a piece of steel that diameter also has the possibility of running into an inclusion or klunker that will mess things up pretty well.Do you know what kind of steel it is.


Yes, it's 1018
 
I agree with most of the points brought up here, except for the part off to 1" diameter then finish with a hacksaw. You should be able to bring your parting tool to about 1/4" diameter and then finish with the hacksaw. No sense in making more work for yourself.
 
I agree with most of the points brought up here, except for the part off to 1" diameter then finish with a hacksaw. You should be able to bring your parting tool to about 1/4" diameter and then finish with the hacksaw. No sense in making more work for yourself.

Disagree.

"If you had to ask...." yah don't have the timed ear and experienced hands, so trying to minimize the saw work is just BEGGING for a crash!

Besides.. parting-off sucks in general on steel solids, softer the worser.

Hollow or bored-past the parting line goods? Whole 'nuther animal!
 
parting is one of my favortite operations.

but if im reading this correctly trying to part off so far away from the chuck is imminent disaster.

takes less than 5min to hacksaw.
 
Just for jollies chuck up a hunk of steel. Part off a small section as close as you can get to the chuck....

Now with that experience behind you think about moving the cut 10 or more inches from the chuck...

Parting off sounds easy but seldom is with out good machinery, sharp tooling and experience.

Band saws do a great job of parting material more than a couple inches from the chuck.
Band saws also cut off material with way less excitement.
 
Just for jollies chuck up a hunk of steel. Part off a small section as close as you can get to the chuck....

Now with that experience behind you think about moving the cut 10 or more inches from the chuck...

How about a tad over eight FEET and in 8" diameter?

Smart move is to saw to length plus minimal skosh FIRST. DO NOT have rough sex with the shop dog and end up SHORT whilst distracted ... and now ya have only a facing operation.

Those are easier, even if yer running heavy with two steadies.

Lathe makes as poor a substitute for a saw as a saw makes for a lathe... but they can still be damned good friends.

:D
 
Sometimes the flat top parting blade is improved with a scallop radius allowing about 5* positive rake to mild steel and a radius going back to blade height, Surface grinder straigh acroos perhaps a 1/8 or 3/16 radius wheel.
 
Sometimes the flat top parting blade is improved with a scallop radius allowing about 5* positive rake to mild steel and a radius going back to blade height, Surface grinder straigh acroos perhaps a 1/8 or 3/16 radius wheel.

HSS? "Usually", not just "sometimes". Same again with fish-mouth front or staggered steps. Anything to curve or split the chip so it don't bind.

Direct support, essentially "negative" stick out is another key. Look at a parting-off tool in the cut. Drop a line straight down from the heel below the cutting tip. No MATTER how deep the plunge, under the blade there's not a damned thing in that gap but ignorant AIR, is there? Even then.. that line can tilt FORWARD. Work is cylindrical, curves AWAY, (I mean.. it's a LATHE, ain't it?) and the material has already been REMOVED, y'see.

Rig so the blade is fully supported, clear down to the top of the cross, NO space to deflect?

Bugger gets a mite more RIGID than average, don't it?

Mind - some of the new Carbide parting systems just make it sooo easy, even *I* might dig pocket-lint and finally spring for one!

:D
 
H

Smart move is to saw to length plus minimal skosh FIRST.

:D

Got it thanks! With my toy lathe before this I couldn't turn any metal over about .75 dia so I am not used to the planning! Chances of this happening again are extremely low! lol
 
Sometimes the flat top parting blade is improved with a scallop radius allowing about 5* positive rake to mild steel and a radius going back to blade height, Surface grinder straigh acroos perhaps a 1/8 or 3/16 radius wheel.

My parting tool has a nice relief on the top face. I haven't used it yet.
 
If the "not so baby" lathe you now have weighs less than one ton, you may not LIKE it, anyway.

Hardinge had a "workable" parting-off system for light lathes. A swing arm with parting tool, pivoted to/at the HS. Look it up. Adaptable? Above my pay grade.

I think she would need to go on a big diet to get down to 1 ton! LOL

P1050331.jpg
 
hey Kev, be careful, "parting between centers" is just not a thing. much like sawing off a limb sitting on the outside..first thing I thought :eek:! there's a reason you didnt see it on line!!!

making a grove for a saw to work in is WAY different than parting, and even so, I wouldn't consider taking say, a 2" dia held between centers down to 1/4, anywhere on a 13" piece, yikes. I dont know how far out you are parting, but imagine if it went bad down at the bottom of the cut and bound up, wrenching the part out of the chuck and jackknifing like a tractor trailer.

THE THING THAT WOULD "CATCH THE PART" MIGHT BE YOUR FACE. (along with the flying shrapnel of the parting blade end going 120 MPH) and it wouldnt be in a predictable trajectory, could ricochet anywhere. a busted parting blade is one of the more dangerous things a lathe can spit at you.

sorry if you already understood all this, but just to make it clear to anyone else looking, felt the need to get that out there. :)

I've hand hacksawed off lots of parts spinning on a lathe, but much smaller stuff, and NEVER between centers. for 2" dia. that doesnt seem like such a great idea even well supported single side near the chuck. its better to start a grove 20% deep max if between centers, take it off the lathe and saw it, put it back on the lathe. cheers, and work safe!
 








 
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