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

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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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
 
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
 
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.
 
.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.
 
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.
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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
 
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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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.
 
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.
Click to expand...

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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