Chatter

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qquake

qquake

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Joined
Feb 8, 2004
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Northern California
Any idea what is causing the chatter? It's only on the right (tailstock) side. It quiets and gets smoother towards the left (headstock) side. It's a fresh edge on my carbide chisel. The blank is a label cast from Wooden Quill. I don't know what kind of resin it is. Each side looks the same, but you can feel that the left side is smoother than the right side. It's on an Ultra-Shear mandrel system, turning at about 2,000 rpm. I'm perplexed.

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Does the same end chatter if you reverse the blank? If so possible poor glue up on that end. If not try taking the bushings out and turning between centers.
 
Couple of things that you might want to try, one move the tool rest closer, and I think if using carbide tools your tool rest height needs to be inline with center of spindle or very close to that based on many videos I have watched on using carbide tools, I have no first hand experience using carbide so I could be out in left field here. The two pictures of your cutters one look dark and other is a bit lighter, are you lapping/sharpening your cutters?
 
I have found that sometimes, I end up embedding into the blank itself little ripples. Even with a sheer cut, there is still heat generated, and with certain materials if you get chatter while its soft, the waves from the chatter end up getting captured by the material. If you feel the blank, you might feel the ripples if they are present.

My tactic is to cut both ways. Cutting the same direction as you did when the ripples occurred will never fix the problem. Cutting the opposite direction should cut through them properly. Might take some lighter cuts the opposite direction to turn it down.

If this is indeed due to ripples in the material you are turning, once they are turned down, the consistent chatter in certain parts of the blank should go away. Then just try to avoid causing it again, otherwise you'll have the same problem again.

I cut with negative rake most of the time for resins myself, although I've tried my hand at sheer cutting, but I've definitely had this issue where if the blank is soft enough and warm enough, chatter in the tool can transfer and harden in the material. It is not necessarily always the cause, there are of course other reasons why chatter may occur in the first place, but when I have chatter problems in exactly the same spot on a given blank over and over, I find that that spot usually has ripples in the material itself.
 
Jim, I have had the very same thing occur on several occasions. I hope you are able to confirm the cause. Usually, I just wind up resorting to sandpaper to get the marks out and get the blank down to the very final size. - Dave
 
wmillman said:
Couple of things that you might want to try, one move the tool rest closer, and I think if using carbide tools your tool rest height needs to be inline with center of spindle or very close to that based on many videos I have watched on using carbide tools, I have no first hand experience using carbide so I could be out in left field here. The two pictures of your cutters one look dark and other is a bit lighter, are you lapping/sharpening your cutters?
Click to expand...
I did move the tool rest closer, but it didn't help. And it's the same cutter in both photos, just a difference in exposure. I don't sharpen carbide.
 
jrista said:
I have found that sometimes, I end up embedding into the blank itself little ripples. Even with a sheer cut, there is still heat generated, and with certain materials if you get chatter while its soft, the waves from the chatter end up getting captured by the material. If you feel the blank, you might feel the ripples if they are present.

My tactic is to cut both ways. Cutting the same direction as you did when the ripples occurred will never fix the problem. Cutting the opposite direction should cut through them properly. Might take some lighter cuts the opposite direction to turn it down.

If this is indeed due to ripples in the material you are turning, once they are turned down, the consistent chatter in certain parts of the blank should go away. Then just try to avoid causing it again, otherwise you'll have the same problem again.

I cut with negative rake most of the time for resins myself, although I've tried my hand at sheer cutting, but I've definitely had this issue where if the blank is soft enough and warm enough, chatter in the tool can transfer and harden in the material. It is not necessarily always the cause, there are of course other reasons why chatter may occur in the first place, but when I have chatter problems in exactly the same spot on a given blank over and over, I find that that spot usually has ripples in the material itself.
Click to expand...
I do cut both directions when I'm roughing. But for some reason, I'm not comfortable moving the chisel from left to right for fine cutting.
 
egnald said:
Jim, I have had the very same thing occur on several occasions. I hope you are able to confirm the cause. Usually, I just wind up resorting to sandpaper to get the marks out and get the blank down to the very final size. - Dave
Click to expand...
It happens a lot to me, when I'm turning acrylics. I haven't figured out what causes the chatter. It doesn't happen with any wood. As for the ripples, wet sanding will take them out.
 
qquake said:
I do cut both directions when I'm roughing. But for some reason, I'm not comfortable moving the chisel from left to right for fine cutting.
Click to expand...
I generally go one direction as well. I have just found that if the waveform of the chatter gets embedded in the blank, the best way to neutralize that is to cut the other way. It basically cross-cuts the waveform (which will slightly spiral around the blank, so when you just cut one direction, you just end up reinforcing that ripple in the blank material).
 
jrista said:
I generally go one direction as well. I have just found that if the waveform of the chatter gets embedded in the blank, the best way to neutralize that is to cut the other way. It basically cross-cuts the waveform (which will slightly spiral around the blank, so when you just cut one direction, you just end up reinforcing that ripple in the blank material).
Click to expand...
It's kind of a moot point now. It's about ready for final shaping.
 

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If the problem only happens when you turn acrylics , and assuming by the term `acrylics` you mean most plastics , I think the problem is a very slight deflection of the tailstock as you apply tool pressure . You won`t encounter it on wood , because even the hardest woods are softer than most plastics . As you move the cutter towards the headstock , the blank has progressively more support because the headstock is totally rigid .

So , make sure the tailstock is firmly locked down . If that doesn`t help , perhaps the bearing in the live center is the culprit .
 
My left to right issues are usually pushing with the left hand going right. Increase downward pressure with the left hand and increase push with the right. Slow down as you get closer to the tail stock. When you start getting chatter.....Slow your cutting...increase or decrease speed. Tool rest as close to the blank as possible. The carbide tool appears to be at an upward angle. Does it need to be more level? Negative rake cutter may improve your cut. My 2 cents.
 
When you get chatter on a metal lathe the first thing to try is slowing down the rpm's, if that doesn't work you increase the feed rate. Try slowing the rpm's, if that doesn't work move your chisel a little faster.
 
You have given me several things to try. The angle of the chisel to the blank (toolrest height), rotation speed (RPM), etc. Unfortunately, the blank is almost at its final size, so I don't know what I'll be able to do before turning is finished. I will raise the toolrest a bit and see if that changes anything during final shaping. The right side of the blank, which will be the tip end, is slightly smaller than the finial end (0.44" vs. 0.47"). My next pen will be acrylic. Well, acrylic and metal, it's a honeycomb blank. So I can experiment a bit with it.

As for the live center bearing, it's an almost new Ultra-Shear mandrel system. This is maybe the tenth pen I've turned with it. It's completely smooth.

One more thing I failed to mention, is that this blank is longer than a lot of the ones I turn, about 3-3/4". So the mandrel shaft has to be out farther. I wonder if that has anything to do with the chatter.
 
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qquake said:
You have given me several things to try. The angle of the chisel to the blank (toolrest height), rotation speed (RPM), etc. Unfortunately, the blank is almost at its final size, so I don't know what I'll be able to do before turning is finished. I will raise the toolrest a bit and see if that changes anything during final shaping. The right side of the blank, which will be the tip end, is slightly smaller than the finial end (0.44" vs. 0.47"). My next pen will be acrylic. Well, acrylic and metal, it's a honeycomb blank. So I can experiment a bit with it.

As for the live center bearing, it's an almost new Ultra-Shear mandrel system. This is maybe the tenth pen I've turned with it. It's completely smooth.

One more thing I failed to mention, is that this blank is longer than a lot of the ones I turn, about 3-3/4". So the mandrel shaft has to be out farther. I wonder if that has anything to do with the chatter.
Click to expand...
Possible. Everything is in play, including debris in the tube by the tail stock bushing. Is the tail stock end square?
Re check everything.
 
Okay, I tried several things. I raised the toolrest. I tried slowing the lathe speed to 1500, then raised it to 2500. I didn't see that the toolrest made any difference. But if anything, the chatter was slightly less at 2500. So from now on, I'll turn acrylics at 2500.


 

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RichAldrich said:
Possible. Everything is in play, including debris in the tube by the tail stock bushing. Is the tail stock end square?
Re check everything.
Click to expand...
What do you mean by "debris in the tube"? Which tube? It's a Jet 1221VS. As far as I know, the tailstock is in alignment, but I'll double check.
 
Well, in spite of the chatter problems, it turned out really good after wet sanding and polishing. I added a couple of steps to my normal polishing regimen. I usually just use Meguiar's 105 and 205. But I added Novus #3 at the beginning, and Meguiar's #9 at the end. I don't know if they helped, but they certainly didn't hurt.
 

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I just experienced the same for weeks (about 6 pens). I changed my live center from the new one I had purchased to the old one and I replaced the handle that holds the ram of the tailstock firmly in place (part 25 circled in red). I believe it to be the latter (the handle), but I replaced both. Since then, no more chatter and no more our of round end on the TS side. I am going to turn some with the new live center and see if it was just a need for a new handle. I didn't have to do anything (yet) with the female cast iron threads that accept the handle.

See part number 25.

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I have several lathes. This happened on my oldest (and most frequently used). I am assuming wear and tear had something to do with it.
 
qquake said:
You have given me several things to try. The angle of the chisel to the blank (toolrest height), rotation speed (RPM), etc. Unfortunately, the blank is almost at its final size, so I don't know what I'll be able to do before turning is finished. I will raise the toolrest a bit and see if that changes anything during final shaping. The right side of the blank, which will be the tip end, is slightly smaller than the finial end (0.44" vs. 0.47"). My next pen will be acrylic. Well, acrylic and metal, it's a honeycomb blank. So I can experiment a bit with it.

As for the live center bearing, it's an almost new Ultra-Shear mandrel system. This is maybe the tenth pen I've turned with it. It's completely smooth.

One more thing I failed to mention, is that this blank is longer than a lot of the ones I turn, about 3-3/4". So the mandrel shaft has to be out farther. I wonder if that has anything to do with the chatter.
Click to expand...
I know how adamant you are against TBC, but there is a very common link between mandrels and chatter that is far more rare on TBC. While you have the Ultrasound Shear Mandrel, it sounds like a minuscule amount of play somewhere on or in the mandrel itself. Flex, play, looseness are the root causes of chatter when external pressure is applied.

TBC is not immune to chatter but has far less parts, and easier to find the problem (alignment, looseness of tailstock). If TBC is a no-no, then the extra problems that arise with alternatives have to be lived with.
 
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TonyL said:
I just experienced the same for weeks (about 6 pens). I changed my live center from the new one I had purchased to the old one and I replaced the handle that holds the ram of the tailstock firmly in place (part 25 circled in red). I believe it to be the latter (the handle), but I replaced both. Since then, no more chatter and no more our of round end on the TS side. I am going to turn some with the new live center and see if it was just a need for a new handle. I didn't have to do anything (yet) with the female cast iron threads that accept the handle.

See part number 25.
Click to expand...
I can see how the live center might cause a problem. But I don't understand how the tightening handle would be an issue.
 
qquake said:
I can see how the live center might cause a problem. But I don't understand how the tightening handle would be an issue.
Click to expand...
If it does not tighten down properly against the tailstock quill shaft, it will allow movement which could produce chatter. This could be from wear on the shaft, wear on the end of the clamp or debris between the two. I discovered this from simply forgetting to tighten it on my HF lathe.

Likelihood will depend on design. My Powermatic P90 does not have a screw against the shaft of the tailstock but a two piece floating clamp-type jaw that tightens against a larger surface area.
 
RichAldrich said:
A piece of glue in the tube that may make your bushings out of round.
Click to expand...
Oh, in the pen tube. I doubt if it was that, I put modeling clay in the tubes before I epoxy them, then clean them with an appropriate sized drill. Plus, the pilot on the pen mill will clean them, too. But in this case, it was a label cast blank. No epoxy involved.
 
qquake said:
I can see how the live center might cause a problem. But I don't understand how the tightening handle would be an issue.
Click to expand...
My handle kept coming loose after I would tighten after a while; I guess from the vibration of the lathe. You have a different issue.
 
I'm a bit late coming in on this but maybe try a roughing gouge, freshly sharpened and gently run it along to cut off the chatter. The extra weight of the spindle roughing gouge will dampen any tendency to chatter.
 
howsitwork said:
I'm a bit late coming in on this but maybe try a roughing gouge, freshly sharpened and gently run it along to cut off the chatter. The extra weight of the spindle roughing gouge will dampen any tendency to chatter.
Click to expand...
I'm not concerned with "cutting off the chatter". It wet sands right out. The chatter is just noisy and annoying.
 
Have you tried a round carbide cutter and/or round negative rake cutter? As mentioned in the other responses, the cutting edge must be at the center line and and the tool held level. I sometimes get chatter turning acrylics. Tool orientation and pressure are sometimes the reason. Watch Mark Dreyer's video on turning acrylic with carbide tools.
 
Jim; The sound of harmonic chatter in your video is distinctive as are the ripples that may appear on the blank surface. The blank is vibrating in time with the cutting tool. Raising the speed may decrease the chatter but to solve the problem, lower the tool rest. Acrylic blanks and carbide tools should always cut at or just below center. This is especially true with very hard or chippy / brittle acrylics.
 
randyrls said:
Jim; The sound of harmonic chatter in your video is distinctive as are the ripples that may appear on the blank surface. The blank is vibrating in time with the cutting tool. Raising the speed may decrease the chatter but to solve the problem, lower the tool rest. Acrylic blanks and carbide tools should always cut at or just below center. This is especially true with very hard or chippy / brittle acrylics.
Click to expand...
It's interesting that you would recommend lowering the tool rest. I normally turn with the tool rest a little lower, but raised it during this. I got chatter both ways.
 
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