# Am I the only one who can't part off on the lathe to save his life?



## dado5 (Dec 31, 2017)

I have really been enjoying my new hobby. Just finished a set of v blocks (not to nearly the tolerances of the youtube video stars, but I'm pleased) and hope to harden them tomorrow. Today I started my next project a fly cutter.  I cut too much off my blank and needed to trim off a 1/4". I figured since I already had it in my lathe I would just part it off.  It is 2" round steel. I sharpen the tool, hone it, make sure it is dead on center and perpendicular to the piece and all I get is chatter and fine little shavings coming off. I slowed my speed down with my back gears to around 160 and used oil.  Any advice?  My next project may be a tool post grinder so I can put a cut off wheel in it!!!!


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## markba633csi (Dec 31, 2017)

Parting off can be tough without a brontosaurus lathe, although some do it well with small machines; I dislike doing it myself. I reach for the hacksaw. 
Mark


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## Chipper5783 (Dec 31, 2017)

Nope.  Challenges with parting off are a very common question.  I had a hard time with it too.  There are several threads on the topic - basically one has to fuss with it.  I have no trouble at all now, and I'm really not doing things much differently - just after a while you're able to sort it out.

Make sure you pull all your slides in, keep the work as short as possible.  I really like the carbide insert part off tools (they work great in the CXA style post).  I find a fairly narrow tool is best (0.125).  Keep at it, you'll get it sorted too.

I set up a rear tool post.  It works great - but the QC tool also works fine and is faster to set up.  It will also depend you what the material is.  Quite often, I'll add some tailstock support (just for the first bit of the cut - don't try to finish a part off task with the tailstock supporting the outer end).


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## Ed ke6bnl (Dec 31, 2017)

if your lathe chuck is NOT threaded on, you might try parting with the blade upside down squared and centered, this is now how I leave the tool on the tool holder, just works better for me on a smaller 11 in lathe.


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## pdentrem (Dec 31, 2017)

Most points involving parting on the lathe

Square to tool to the work and on center line.
Tighten your gibs. 
Sharp, very sharp, extremely sharp, did I say sharp, Tool!
Work held as close to chuck as possible.
Thin tool is better as a parting tool is taking a heavy cut like a form tool. Only have enough tool sticking out to reach just past the center of the cut. Too much overhang means a squirmy tool.
Cutting oil. 
Very rigid tool holder, here the lantern is second best to most tool holders. 
RPM is machine dependent, on the Atlas back gears is the highest I had success with. On heavier more stable machines even normal turning speeds are possible. 
Feed the tool in as too light a cut will cause issues. When I hand feed, it is about 0.001” or more per revolution.
Pierre


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## paws-fixit-shop (Dec 31, 2017)

I'm a learn as I go hobby guy to, and I recently cut my spindle speed way down for parting.  My lathe is an Atlas 10F, and I part with it in back gears and the next to slowest setting which I think is about 45 rpm. I find that by taking just about .005 per revolution (on 1" or smaller stuff) it works a LOT better now.  I'm using an HSS cutoff tool in an AXA tool holder and lots of oil.


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## benmychree (Dec 31, 2017)

In addition to the above responses, I add that a tool holder that causes the tool to overhang the cross slide to the side can also cause trouble with the tool trying to twist counterclockwise and dig in and chatter. I think the lantern tool post is better in this respect, especially if the rocker ring is done away with and a new washer is made for under to tool holder of such a thickness that brings it on center.  I did this with a 1916 vintage American High Duty lathe that I had years ago, and enjoyed much less parting tool breakage.
You might also look at headstock spindle bearing adjustment,; if a bit loose it would induce chatter; sometimes good also to run a center in the part until it is nearly cut off to reduce chatter.  I use Tap Magic for parting off with HSS, and water based coolant for carbide insert parting.


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## higgite (Dec 31, 2017)

dado5 said:


> ... I sharpen the tool, hone it, make sure it is dead on center and perpendicular to the piece and all I get is chatter and fine little shavings coming off.....


Since everything else seems to be up to snuff (cutting edge centered, etc), your parting tool may not have enough front relief and you're getting rubbing instead of cutting. And please don't take this the wrong way, but the spindle isn't turning the wrong way is it? (Somebody had to ask. )

Tom


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## Technical Ted (Dec 31, 2017)

dado5 said:


> I have really been enjoying my new hobby. Just finished a set of v blocks (not to nearly the tolerances of the youtube video stars, but I'm pleased) and hope to harden them tomorrow. Today I started my next project a fly cutter.  I cut too much off my blank and needed to trim off a 1/4". I figured since I already had it in my lathe I would just part it off.  It is 2" round steel. I sharpen the tool, hone it, make sure it is dead on center and perpendicular to the piece and all I get is chatter and fine little shavings coming off. I slowed my speed down with my back gears to around 160 and used oil.  Any advice?  My next project may be a tool post grinder so I can put a cut off wheel in it!!!!



Parting can be one of the biggest challenges on a lathe... the smaller and less rigid the machine the worse it gets. There are a lot of variables at work here, so I'm just going to throw out some random thoughts. Sometimes, little twists can make a big difference. YMMV depending on your setup, equipment, material, experience, etc..

1- This is a big one here. If I only needed to remove 1/4" I would not have parted it off... I would have just faced it off. Much safer and in the long run, much quicker. Or, since it was 2" diameter, if I had more to remove that 1/4" I most likely would have taken it off and put it on my band saw. For me parting small diameters is pretty easy/safe, but larger diameters, especially on smaller lathes, I would only part as a last resort. 
2- I usually will have my parting tool above center to help keep the work piece from climbing over the top and breaking my tool. As you get closer to center the tool will stop cutting because it is too high and at that point I will back the tool out, lower it down a little and continue parting doing this at many times as it takes. You can tell when it stops cutting because you will feel it while hand feeding.
3- I've had my best results will only grinding ~5 degree clearance on my HSS parting tools. More seems to cause more chatter.
4- Part as close to the chuck as possible. If out a ways, lightly put a center in the end if you can. Don't apply much pressure or, if you do, back it off before you break through. This will help stabilize and help keep the part from climbing over you parting tool and breaking it.
5- Keep you parting tool as short as possible. On deep parts start with it out only a small amount and stop when you run out of length and lengthen your tool. The shorter you can keep it as you go, the better.
6- Use a good grade of cutting oil. Don't be bashful with it.... slop it on good. You want those chips to flow out easily and not get hung up. If they do, you're in trouble.
7- Here's a tricky part... sometimes when you get chatter you have to feed in harder to get a good chip started and stop the chatter. Of course if you feed in too hard you're in trouble. This can only be learned by experience and it is still a risky maneuver. It takes some finesse! 
8- Run the lathe as fast as you can without chatter and from burning up your cutting tool. If you run it very slowly, and sometimes you just have to, it can be very difficult to feed it in by hand at a nice, gradual, steady pace. It's very easy to feed too fast and then you're in trouble.
9- Make sure your tool is exactly perpendicular to your work. 
10- I usually grind my tool at an angle so the piece drops off leaving the burr on my stock. But, this angled grind can cause the tool to want to walk off sideways so only use a very slight angle or none at all. 
11- The narrower the blade, then less likely to chatter. But, the more likely to break because it is weaker.
12- Lock your carriage in place.
13- Take the slop out of your compound slide.

There's my 5 minute brain dump! 

Did you notice how many times I said you could get into trouble? 

YMMV and I'm sure others have suggestions and may very well disagree with some of what I've said, but these are things that I have tried over the years with some success.

Good luck,
Ted


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## eeler1 (Dec 31, 2017)

What they all said.  I find that even after executing all of those suggestions, some materials just resist being parted off on the lathe.  I have a couple feet of mystery steel rod, I don’t know what it is, just that it hates being parted.  Grab, chatter, etc, I get all possible parting ills trying to cut this heinous material.

Maybe practice on delrin or something similar to get your confidence up, then part something tougher.


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## chips&more (Dec 31, 2017)

I can part on my Levin watchmaker size lathe, no problem. I can part on my Clausing 14”, no problem. But when I had that Senica Falls 9”, it would chatter if I just looked at it. That lathe taught me a lot about proper spindle end shake adjustment and gib adjustment to name a few. In my experience it was bearing preload that had the most effect on chatter. That’s with no cracks in the carriage assembly. And a very sharp pointed tool bit for the least amount of tool pressure. Parting on that Senica Falls was hard on the sphincter. I didn't cry one bit when that Senica Falls lathe went away…Dave


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## Glenn Brooks (Dec 31, 2017)

I have constant trouble parting with cheap, hobby quality, parting blades, and no problem whatsoever with high quality blades.  I’ve come to the conclusion that our hobby suppliers love to sell pretty looking junk steel parting blades. They look great but break constantly, causing an endless consumer demand for inferior, unsuitable parting tools.  

Try buying one top of the line parting blade and see if it makes a difference. My guess is, your parting problems will go way down.

Glenn


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## Ulma Doctor (Dec 31, 2017)

i try to part with 8% Cobalt whenever possible, for my machines.
i haven't seen better results in varying materials during parting operations.
Carbide cut off inserts are very nice, but i break them at inopportune times.
i try to resist the urge to pull what's left of my hair out, so i just put a cobalt parting blade permanently in an AXA holder and use it for EVERYTHING


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## Ray C (Dec 31, 2017)

Very important rule...  Position the cutter and point of blade contact so it's as close-in to the center of the carriage as possible.  In other words, don't have the compound extended at all or, to the left or right.   Keep the cut close to the chuck but not so close that you need to extend the compound to reach the cut.   This makes a day and night difference.  Use all the advice that others provided too.

Finally, some lathes are just too light-weight and/or clapped-out to accomplish parting.  If the lathe cannot competently handle carbide tooling on steel with 25-30thou depth cuts, the lathe is probably too lightweight for parting.   Carbide tooling works because of high pressure.  Parting needs high pressure (regardless if you use a HSS blade or carbide parting blade) so, if it can't handle carbide, it probably can't handle parting.   This is not some machinist fact by any means.  It comes from my experience of using quite a few different lathes over the years.   Your mileage (or somebody else's) may vary.

Regards

Ray C.


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## T Bredehoft (Dec 31, 2017)

.001 to .005 is probably not enough feed. Ray, above, mentions 25 to 30 thou, That might be what it takes. I   don't pay any attention to feed, (no power cross feed) I crank it in 'til it cuts. Slow RPM on something as big as 2 inches, really slow, lock the saddle to the rail, tighten the compound gib and feed in the cross slide as hard as  you can. It will either cut or stall the lathe.


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## Ray C (Dec 31, 2017)

T Bredehoft said:


> .001 to .005 is probably not enough feed. Ray, above, mentions 25 to 30 thou, That might be what it takes. I   don't pay any attention to feed, (no power cross feed) I crank it in 'til it cuts. Slow RPM on something as big as 2 inches, really slow, lock the saddle to the rail, tighten the compound gib and feed in the cross slide as hard as  you can. It will either cut or stall the lathe.



Hold on now...  You don't take 25 to 30 thou with a parting blade.  No way.   If you can't take a 25-30 thou cut with your lathe using carbide tooling then, your lathe is probably not rigid enough to do parting.   That was my intended message.

Ray


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## NortonDommi (Dec 31, 2017)

Like *Ed ke6bnl *I run my part-off blade upside down. I knocked up a holder in a hurry so it is not pretty but it works,one day I'll remember to buy some countersunk screws for it.  *benmychree * raised a point that I think is quite important and that is the offset from the center of the toolpost. The holder I made,(photos attached), was fabricated from the scrap bin but does bring the center line of the blade much closer to the center of the tool post. I check that the blade is square to the lathe axis *every time *I use it. Locking down your apron and tightly adjusted gibs with minimal play is a must and as has been mentioned an aggressive feed.
  That said I use a lot of 'mystery metal' and some stuff just does not want to be parted. I've even had stuff work harden while I'm cutting it and then strip the teeth from the bandsaw blade when I swop to that!
  New Years resolution is a dedicated rear toolpost.
   All the best for the New Year to all.


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## woodchucker (Dec 31, 2017)

T Bredehoft said:


> e saddle to the rail, tighten the compound gib a*nd feed in the cross slide as hard as you can*. It will either cut or stall the lathe.


What??? Nooooo, you will dig in, you want to cut. There is a sweet spot to the feed. You have to feel for it.


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## dado5 (Jan 1, 2018)

thanks for the replies. I will try some things today.  As far as the lathe, Yesterday I was taking .060 cuts with carbide inserts and it came off like butter, so I think I should be able to part with it. Will get back to you with an update.


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## Karl_T (Jan 1, 2018)

dado5 said:


> thanks for the replies. I will try some things today.  As far as the lathe, Yesterday I was taking .060 cuts with carbide inserts and it came off like butter, so I think I should be able to part with it. Will get back to you with an update.



OK, this makes a big difference. Your lathe is rigid enough to move up to carbide inserts for parting. Manchester makes the best ones. Switch to these and your parting woes will be over. I use 0.007" per revolution feed and just engage the cross slide. Cuts off like butter every time.  NOTE this will not work on lathes not rigid enough.


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## Silverbullet (Jan 1, 2018)

There's a YouTube video with a guy who uses a steel plate  across the ways and the cut off tool has a shaft that rides on it to stop the cutter from flexing . Small LATHES don't have the heft to not move when parting . You can alter the cutter geometry to help too. Parting blades with a tiny notch in the center seem to cut easier thus less pressure when feeding . I'd suggest cking some of those also


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## Cheeseking (Jan 1, 2018)

Glenn Brooks said:


> I have constant trouble parting with cheap, hobby quality, parting blades, and no problem whatsoever with high quality blades. I’ve come to the conclusion that our hobby suppliers love to sell pretty looking junk steel parting blades. They look great but break constantly, causing an endless consumer demand for inferior, unsuitable parting tools.
> 
> Try buying one top of the line parting blade and see if it makes a difference. My guess is, your parting problems will go way down.
> 
> Glenn



A lot of good suggestions but what Glenn mentioned above helped me a ton. I used to part using this and 50% of the time much excitement ensued!


Finally sprung for this and wow- night and day difference. (Don't mind the excessive stickout on mine. I frequently part off 3"+ diameter nylon so that why I have them set so far out.) Set the blade for the minimum stick out possible.


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## dado5 (Jan 1, 2018)

Well i got it parted off.  I think my main problem was the tool.  I reground it and spent more time honing it until it was really sharp. made a huge difference. I also slowed the speed as slow as my lathe would go.  There is definitely some art to it though.  Even with this if I fed too slow it would start to chatter, so against my will I fed in faster and it would cut awesome curly chips! But…..too fast and chatter again.  Have to learn the feel i guess.  Thanks for all the help. I will also buy one of the above tools.


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## middle.road (Jan 1, 2018)

Joe Pie has a decent video up, and he mentions the same thing that UlmaDoc mentions above about the percentage of cobalt.
 -=- LINK -=-
I use surplus from the auctions. Have a few  HSS 1/2 Armstrong #86-257's and their geometry is 'Right or Straight' They are square/perpendicular on one side.
Then I have some other wider ones that I need to get some holders for, and then a couple of carbide insert styles that I hold in reserve because of the cost of the inserts.


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## Cactus Farmer (Jan 1, 2018)

I,to, had troubles parting off. Started with a tiny thin blade with uncoated inserts. Not much joy. Was forced to try coated inserts and WOW, what a difference. I then went to a thicker blade in a custom made holder <designed to get the blade closer to the center of the QC tool block. Again, a great increase in my abilities to preform the work. I now have a CXA block with much more robust tools and holders. Mass is good!!! Tight is just as important! I seldom break an insert and usually replace them when they are acting up before failures occur. Lastly I had to learn you can't sneak up on a cutoff operation. Feed it more that you would ever think it would take! And make sure it's square to the work! Good luck, and keep us informed of your progress!


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## kd4gij (Jan 1, 2018)

I find parting on my 4x6 to be a breeze.


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## savarin (Jan 1, 2018)

I found those "T" cross section parting blades work exceedingly well on my floppy 9x20.
My solid plinth instead of a top slide/compound also made a gigantic difference.


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## Doubleeboy (Jan 1, 2018)

Lots of good info here in thread.  I will add make sure, absolutely sure you are on center, and that blade is square to chuck, to be sure, dial it in with test indicator, even being off a thou or two can make parting a nightmare.  I like sulfur cutting oil for steel, kerosene for aluminum, dry for cast iron and plastics.  Lots of cutting oil on steel and keep the feed up, if you baby it, you can get work hardening and then when you add more pressure and start cutting again you get a big dig in and snap, the sound of more money down the tubes.


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## higgite (Jan 2, 2018)

Cheeseking said:


> Finally sprung for this and wow- night and day difference. (Don't mind the excessive stickout on mine. I frequently part off 3"+ diameter nylon so that why I have them set so far out.) Set the blade for the minimum stick out possible.
> View attachment 252663


Cheeseking,

What machine are you using that it makes such a difference? Something rigid, like a Bridgeport, or something not so rigid, like a mini mill, or something in between? Thanks.

Tom


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## jlsmithseven (Jan 2, 2018)

You're in the same boat as everyone, parting off is a pain...but you learn what works and what doesn't. Keep at it!!


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## fast freddie (Jan 2, 2018)

no your not the only one, I can't part very good also


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