Lathe Question. parting..

Doc H.R. · Sep 16, 2013

i am new to machining, just got a 1340 and working on honing in my skills.

i am looking for some tips on parting. i can't seem to part much more that 1 inch with out trashing my inserts. as well as i get some really bad vibrations. i wonder if my turning speed is not right? and i assume that the inset should be cutting at the center point?

any help or other additional tips would be great!!. thanks!

Forestgnome · Sep 16, 2013

It's been covered pretty regularly, search for parting.
The basics:
Tool on center.
Tool as close to the chuck or collet as possible.
For steel, continuous addition of heavy sulphurized oil in the groove or flood coolant.
Power crossfeed if you have it.
As little tool extension (stickout) as possible.

Reasons for chatter are violating any of the above.

proturn · Sep 16, 2013

Parting off in a manual is always tough on inserts. Follow these steps:
1. Use the correct insert grade for the material you are cutting.
2. make your setup as rigid as possible. also make sure your cutting tool is straight with the world.
3. set your tool to just above center, .01" inch will work. In a manual lathe, your part will always try to ride over the top of the cutting tool so setting it just above center will insure that under pressure the tool is cutting on center.
4. listen to the cut. Is it Chirping? slow down the rpm. Still chirping? speed up your feed.
5. use air blow or cutting oil to cool off the part and to clear chips from building up.

Zonko · Sep 16, 2013

If it makes rumbling, ripping or otherwise "gritty" sounds.....it wants more lubrication.

toolsteel · Sep 16, 2013

I am sure some will look down their noses a bit when I say this....but.....for me if I am doing a one-off part on a manual lathe, I have gotten to the point of saying to hell with the cut off. I throw it on the saw, cut it off, then face the backside. Obviously not an option if trying to do some production parts in a manual late.

larstonx · Sep 16, 2013

Glad I'm not the only one who has a hard time.
Tool perpendicular to the workpiece, lock carriage, slow RPM, high feed, flood coolant, close to chuck, minimum tool extension, slightly above tool center.. Seems to work, but can get hairy on the large diameter stuff!

Don Clement · Sep 16, 2013

I have had no trouble parting off on a manual lathe with an Iscar Dogrip insert cutting tool. The geometry of the insert produces a chip narrower than slot being cut. Shown below is a 3.8” diameter aluminum round parted off in a manual chicom 12x36 lathe. I have no fear parting off with a manual lathe using the Iscar DoGrip parting tool.

Don

adama · Sep 17, 2013

Gummy mild steel, im in the just saw it camp when it comes to a manual lathe + limited coolant flow. I will happily manualy part anything else though, from plastic through to 304-316 stainless.

Doc H.R. · Sep 17, 2013

Thanks guys!! definaly some good tips here. i have been using the saw and facing the back side, but a time the pieces are pretty small or thin to be getting it back in the machine. as well as i think it shouldn't be any issue using the tool to its potential, just need to have the technique down.

i think speed is the biggest part of my problem, i generally don't turn the material too fast, and i try to use minimal pressure as to not jamb up the insert. when it breaks and jambs inside the groove i have an new issue.

proturn · Sep 17, 2013

Doc H.R. said:
Thanks guys!! definaly some good tips here. i have been using the saw and facing the back side, but a time the pieces are pretty small or thin to be getting it back in the machine. as well as i think it shouldn't be any issue using the tool to its potential, just need to have the technique down.

i think speed is the biggest part of my problem, i generally don't turn the material too fast, and i try to use minimal pressure as to not jamb up the insert. when it breaks and jambs inside the groove i have an new issue.

If you don't have enough rpm, the insert cant cut properly and the material will grab it and break the tool.

Zonko · Sep 17, 2013

Not quite true....a good insert will make it through most reasonable materials at very low rpm as long as you flood the cut with a good cutting oil...

If the cut sounds like a regular cut....you are ok.

If it sounds bad....it is bad...

Nick Mueller · Sep 17, 2013

Oh, people here do cut with RPM, not surface speed. :nutter:

Well that explains a lot!

Read the specs for the insert and follow them. They do give values that to make sense and that do work. Don't be tempted to reduce the feed. And adjust to center height. If you adjust above, you ask for chatter.

Don't use oil, unless the manufacturer specifies it. Some inserts don't like oil at all.

Nick

proturn · Sep 17, 2013

Nick Mueller said:
Oh, people here do cut with RPM, not surface speed.
Well that explains a lot!

Read the specs for the insert and follow them. They do give values that to make sense and that do work. Don't be tempted to reduce the feed. And adjust to center height. If you adjust above, you ask for chatter.

Don't use oil, unless the manufacturer specifies it. Some inserts don't like oil at all.

Nick

Nick, The OP stated that he didn't know a lot about turning. RPM is universally known. SFM is a foreign language to a novice.

rpchristian · Sep 17, 2013

You can also try creating a wide groove to allow chips to escape by shifting the tool back and forth on the topslide: leave enough material to do a final pass across the whole face. Something else to try that mght improve chip-escape is to flip the tool and run the lathe in reverse.

Zonko · Sep 17, 2013

proturn said:
Nick, The OP stated that he didn't know a lot about turning. RPM is universally known. SFM is a foreign language to a novice.

And....what matters more.....

The typical manual lathe has only few gears and no VFD.

Now we have a new one, no experience with it yet. A good machine.
But lets talk the old one.

(These RPM values are rounded)
really f****** slow....lots of speeds you dont need 80% of the time
280
350
500
800
1000
1600

The insert can do a 2" steel workpiece at 800 rpm, no sweat.
The machine can not.
That leaves only 500 and 350, depending on material. Sometimes even slower. 200 or so.

I dont need sfm if my machine has only 2-3 speeds relevant to parting off any certain workpiece size.

For all intents and purposes its reduced to high,low, and intermediate rpm.
Flick the levers....dont even think the numbers. This chatters. Flick lever 3 over. Still chattering ? Flick 3 back and 2 over. Now at 350....lots a oil. Crisp clean chrips without signs of rubbing or chatter. Good.
Parted 3" steel that way on a crappy Colchester Bantam ...which is less than 1000pounds....

Listen to the machine....it will tell you a lot...
And yes, put the tool on center. Old crappy HSS blades may flex. A good insert sword is ridiculously strong and stable.

And if you cannot push the mfg's SFM recommendations because the machine cannot handle it...all of Nicks "no Oil talk" becomes old...very fast. If your cutting parameters are too low to prevent built up edge.....lubrication is the only way to stop the horrible groaning and grabbing .
Canola oil....LOTS of it.....works just as good as most of these modern "green" cutting oils. (Which are more often than not vegetable based too).

If you have flood....use it....

CalG · Sep 17, 2013

I really do enjoy the VFD when parting off

"Poor man's Manual machine constant surface speed.

Set the VFD for 20hz at the start of the power in-feed parting op. Then dial in VFD/spindle rpm to keep the sound right ;-)

Cutting juice as required!

What a deal!

Nick Mueller · Sep 18, 2013

The OP stated that he didn't know a lot about turning. RPM is universally known.

As the OP didn't mention any RPM, my remark can only have been directed towards the answers.
The OP didn't even give a diameter (except that he can't part off with more than 25 mm diam).
No mentioning wether it is aluminium, brass, leaded steel 4045 QT.

But he gets answers what RPM to use. :nutter:

Nick

Don Clement · Sep 18, 2013

I should have mentioned that I use the same Iscar DoGrip parting insert for aluminum, stainless steel, and Turcite rod with equally excellent results. The difference is that I use Relton A9 with aluminum, Mobil Omega oil with SS and a Vortec air gun or dry with Turcite rod.

Don

NAST555 · Sep 18, 2013

Forestgnome;2117892 Power crossfeed if you have it. [/QUOTE said:
All Of your other points I agree with but power feeding with a manual when you do not have too much experience You need to first know what it sounds and looks like before you need to hit the ground! If you pick up chatter either your speed is too fast or your feed is too slow. If you get insert wear, not breakage, are your chips freely flowing out of the groove. If you get breakage is your tool set up on the correct height and is your part "catching" not interfering with the insert. Is the blade flexing because of too much sickout. Is the finish jagged because of chip rubbing? All these things, in my opinion, cannot be taught with using a power feed.

Forestgnome · Sep 18, 2013

Wow, arguing against the use of SFM on this forum? It's better learned than avoided. On the power crossfeed thing, you can avoid a lot of setup problems by babying the feed manually, but you might never know how fast it will cut until you power feed it. It'll give you confidence once you get it right.

Lathe Question. parting..

Plastic

Stainless

Stainless

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Titanium

Plastic

Cast Iron

Diamond

Plastic

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Stainless

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Aluminum

Stainless

Diamond

Titanium

Cast Iron

Stainless

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