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Posted: 1/5/2015 3:18:02 PM EDT
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Hi Guys,
I'm having a hell of a time with parting tools. I started with regular plain old cutters in an aloris holder, and haven't had good luck. They either chatter if I'm not cutting fast enough, or the heat up and dull if I go fast. I seem to have the same problem on reg steel or stainless.I've tried spinning fast and slow, oil/no oil/ feeding fast or slow. I don't get it. I then bought this: http://www.latheinserts.com/PART-OFF-INSERTS_c90.htm thinking the world was my oyster, and broke it off in 3 minutes cutting 316. It chattered at first, I tried feeding a little faster, and snapped the bottom of the jaw that holds the insert right off. What should I buy? My tool holders hold up to 1/2" tools. |
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I use the plain ol’ parting tool in the QC type holder and generally have no problems. I’ve resharpened it several times and always hone the cutting area. I run about 80rpm and use plenty of dark oil (and back out often to clear chips).
Is the tool going straight in? Set up right on center to maybe just a hair below? How much tool is sticking out in front of the holder? Have you always had the problem - or was it working fine and now something has changed? |
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Quoted:
I use the plain ol’ parting tool in the QC type holder and generally have no problems. I’ve resharpened it several times and always hone the cutting area. I run about 80rpm and use plenty of dark oil (and back out often to clear chips). Is the tool going straight in? Set up right on center to maybe just a hair below? How much tool is sticking out in front of the holder? Have you always had the problem - or was it working fine and now something has changed? What he said plus watch your tool feed rate. Too fast you dig in and too slow it chatters. Smooth and steady so you are cutting a curl. Emphasis on GunCats dark oil. I like an acid brush dipped in oil held in the kerf, wets it nicely and is fairly neat. |
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It does seem like it got worse over time.
I inherited a pretty wide cutter that did ok for a while. It was somewhere around 3/16" wide. I ordered a much thinner one, and never had good luck with it. I do take the tool, and set it flat against the workpiece that I've trimmed off square, so I'm fairly sure that I'm square. I only eyeball that I'm coming in at center, is there a better way? |
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Quoted:
It does seem like it got worse over time. I inherited a pretty wide cutter that did ok for a while. It was somewhere around 3/16" wide. I ordered a much thinner one, and never had good luck with it. I do take the tool, and set it flat against the workpiece that I've trimmed off square, so I'm fairly sure that I'm square. I only eyeball that I'm coming in at center, is there a better way? Stick a 6" ruler between the cutter and stock. Straight up and down is a good indication of the tool bit being on center. If the ruler leans in or out the bit is too high or low 
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Quoted:
What he said plus watch your tool feed rate. Too fast you dig in and too slow it chatters. Smooth and steady so you are cutting a curl. Emphasis on GunCats dark oil. I like an acid brush dipped in oil held in the kerf, wets it nicely and is fairly neat. Quoted:
Quoted:
I use the plain ol’ parting tool in the QC type holder and generally have no problems. I’ve resharpened it several times and always hone the cutting area. I run about 80rpm and use plenty of dark oil (and back out often to clear chips). Is the tool going straight in? Set up right on center to maybe just a hair below? How much tool is sticking out in front of the holder? Have you always had the problem - or was it working fine and now something has changed? What he said plus watch your tool feed rate. Too fast you dig in and too slow it chatters. Smooth and steady so you are cutting a curl. Emphasis on GunCats dark oil. I like an acid brush dipped in oil held in the kerf, wets it nicely and is fairly neat. Feed rate is more important than RPM with a parting tool. ETA: only hang out enough tool to get to the center of the part. |
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Being centered is not really a Mk1 eyeball operation. Are you using a 3 jaw chuck?
When I had a lathe I would chuck up a similar sized piece of stock and draw across it till I was certain I was centered. Never really had chatter problems. Unless I just had way too long of a barrel in there. How far from the chuck are you cutting? |
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Quoted:
Being centered is not really a Mk1 eyeball operation. Are you using a 3 jaw chuck? Quoted:
Being centered is not really a Mk1 eyeball operation. Are you using a 3 jaw chuck? Yes Quoted:
When I had a lathe I would chuck up a similar sized piece of stock and draw across it till I was certain I was centered. Never really had chatter problems. Unless I just had way too long of a barrel in there. How far from the chuck are you cutting? I typically have the cutter out just a bit more than an inch. |
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Standard HHS and insert tool will work just fine,( they are not the problem, its you).
Step one, don't hang the cut off tool farther than you need to cut inwards to part off. Use the chuck head to make sure that you have the cutter square to the stock, hence move the carriage over to the side of the chuck, put the side of cutter to the face of chuck, then lock the tool down when you have it square to the face of the chuck. In the case of HSS cut off tools, sharpen them every time (large side is your cutting edge, and the thinner side is your trailing edge). You don't need to get fancy with a chip breaker, but they do not come sharpened to start with, so you need to sharpen a HHS parting tool the first time to use it). Also, slow the spindle speed down, and keep lube in place. By spinning the spindle too far, you are just creating unneeded heat on the part, which will cause the HHS insert to dull even faster. Feed rate, let the cutter cut at a steady rate, instead of over feeding the cutter in too fast to crash the machine instead. Lastly, lock the carriage before you state to make the parting cut, hence nothing worse then the carrrige moving as you are trying to make a part, since the tool will try to dig into one side and cause a lot of chatter. As for insert cutters, faster to use since you don't have to sharpen them every time, but gets spendy quick since when the become dull, you have to replace the insert (hard to sharpen, since there is so little to hand on to regrind the carbide inserts). https://www.youtube.com/watch?v=fZlWJ_JqQtA |
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