Vibration/ chatter problem driving me nuts

[Brian Brown]

I have a Delta 46-460, and I have a problem I have never heard of before. I get a serious vibration when I mount a "platter" style blank. Anything over about 8" in diameter gets a huge vibration. The lathe is firmly mounted to a heavy cabinet, and the problem seems to occur with thin large diameter pieces. When I mount a larger 8-12" diameter HF blank I will get a little vibration until it is trued and balanced, then the vibration goes away, and I can turn the speed up. With the thinner platters and bowls, the vibration is terrible even when the blank is trued. I turned a 2.5 inch deep 11.5 inch diameter bowl Saturday, and it vibrated so hard everything on my shelves below bounced out onto the floor. This bowl was screwed to a face plate, turned the outside with a tenon, reversed with tenon in a chuck, turned the inside, and sanded, my usual proceedure. The vibration is reduced slightly when I am cutting, and worse when the blank is spinning without a tool touching it. Speed doesn't seem to matter. Putting the tail stock against it doesn't help. I don't really get much chatter marks from turning with the vibration, just a slightly wavy surface that can be sanded out. I have only tried a few blanks like this so I don't know if it is the wood, the lathe , or my technique. It is usually my technique that causes problems. Has anyone seen an issue like this with the 46-460, or any other lathe? Any advice?

[Russell Eaton]

Have you checked the set screws to see if they are tight. I know there are several that can loosen over time and they could be the culprit.

[Roger Chandler]

If all your set screws and such are tight...........it could be that a thin platter style blank is getting oscillation and that is causing the vibration.......the density from one part of a blank to another can be different....some grains are heavier than others and sap wood holds more moisture than heartwood, in general, so you might be experiencing the oscillation developed by different densities in the wood itself as it spins..........the thinner the blank the more noticable it might be as well......just a thought.

[Brian Brown]

Which set screws would I check, and where are they? I know the set screws on the face plate were loose. I was not planning to turn in reverse, so I didn't tighten them. Are there others to check?

[Roger Chandler]

Which set screws would I check, and where are they? I know the set screws on the face plate were loose. I was not planning to turn in reverse, so I didn't tighten them. Are there others to check?

Hi Brian.........I don't use a 46-460, but thought you might be using a chuck, and if the set screw is not tight on the insert, then wobble/vibration can occur............since you are using a face plate, then I would say you have an unbalanced blank of wood, even though it may be true/round after turning it. That does happen occasionally.

[Robert Henrickson]

If all your set screws and such are tight...........it could be that a thin platter style blank is getting oscillation and that is causing the vibration.......the density from one part of a blank to another can be different....some grains are heavier than others and sap wood holds more moisture than heartwood, in general, so you might be experiencing the oscillation developed by different densities in the wood itself as it spins..........the thinner the blank the more noticable it might be as well......just a thought.

But the blank which he says vibrated so bad was at least 2.5" thick and described as a bowl rather than a platter ("turned a 2.5 inch deep 11.5 inch diameter bowl Saturday, and it vibrated so hard everything on my shelves below bounced out onto the floor") -- hardly what I would consider particularly thin and likely to oscillate due to thickness/thinness (in the last few days I've turned several platters 14-16" in diameter from 4/4 stock -- I think that is thin for the diameter and more likely to oscillate). I would agree that differential density sounds like a more likely explanation, but having the same problem with several pieces may indicate some other problem, such as fasteners.

[Prashun Patel]

Brian-
I have the same lathe. I don't tighten the 'grub' screw on the faceplate either. The screws they're talking about are 8 that connect the jaws to the chuck.

Mine vibrates too when things are out of true at very high speeds. What speed are you turning at?

Also, what kind of wood have you been using? I once had a 12" oak crotch that would not turn vibration-free even when round. I still have the scar from when it worked itself loose and flew at my chest.

Thin platters and bowls do chatter on me; but they don't cause my stand to vibrate. The chatter is mitigated by using a bowl steady.

[Russell Eaton]

You have set screws on both pulleys and the handwheel. Mine will loosen from time to time. If you ba s the rivht "T" handle it will be easier to do.

[Reed Gray]

It is true that some pieces will never balance out, no matter what you do. With these pieces, you have to use lower speeds. That is the good thing about variable speed. Turn it up till it starts to wobble, then back off a bit. Some bowls I can turn at 2000 rpm, and others at 500. It just depends.

If that isn't the problem, then some thing is loose. Platters do tend to flex more than bowls, in part because they are flat as compared to curved, and in part because we tend to turn them thinner. Sounds like some thing else may be going on here. When I mount with a face plate, I put the screws in and tighten them like I do with lug nuts on a car wheel. 12 o'clock first, then 6, then 3 then 9. I don't go round the clock in order. When tightening up the screws, I don't use maximum torque on the drill, but just enough to get the screw down. With harder woods, you may have to drill pilot holes. After all screws are tightened the first time, then I go round one more time to tighten them down again. If even one of them is loose, then you get wobble. Of course, you need a really flat surface to mount the face plate on. If I have an irregular surface, I use a forstner bit and the depth stop on my drill press as the most simple method. Once the blank is mounted on the lathe, if you can wiggle it at all, there is a loose screw.

robo hippy

[Roger Chandler]

Very good points Reed............that mounting of the face plate can be an issue as well................good luck Brian!

[Brian Brown]

I thought about the density differences, and it seemed that this one would be fairly consistent, but what seems to be the case, isn't always. The wood was ash. The chuck jaw screws were tight when I started, because I had just replaced the jaws. I don't tighten them down very tight because then I can't get them out. It is possible that one or more came loose. I haven't used the chuck since that bowl. so I can check that when I get home tonight. I didn't think about the grub screws on the pulleys, so I will definitely check that. This happened on a wide shallow bowl a few weeks ago, and I have turned a few things since, and no problem with the longer smaller diameter stuff. The problem happens at all speeds, and the severity appears to be roughly linear as the speed increases. My chuck does not have an insert, but is correctly sized for the spindle, and I have had no problem with it in the past. The chuck is about 3 years old. I have a bowl steady, but the largest diameter I can use it with is about 10.5". I might have to make a new one. I am really hoping to solve this problem because I have some ideas for a few turnings in the near future that are thin and large diameter like thin platters. These will be delicate, and vibration will kill me. Thanks everyone for the replies so far. I'll let you know if I figure it out.

[Robert Henrickson]

The 14-16" diameter plates I turned from 1" planks were ash; final thickness was 1/4" or less. Once trued I had limited problems with vibration, and what there was certainly was due to the complex profile I was turning. Looks like something to do with fasteners -- I have almost never used a faceplate, so the need for a flat surface to attach it to didn't occur to me.

[Russell Neyman]

This sound so elementary, but I'll toss it out anyway: Start the lathe with nothing mounted (not even a chuck) and crank it up all the way. If it vibrates, it's something internal, like a worn belt or loose screws. If that reveals nothing, mount a chuck and do the same thing. I've heard of mis-balanced faceplates and chucks, so you should eliminate the obvious first. Good luck with this, and keep us posted.

[Rick Markham]

I was experiencing a similar vibration occuring with my PM 3520B, (this is 741 lb machine). I had recently moved it, and was getting a strange vibration on all speeds with a unbalanced workpiece, I was also getting some "interesting" harmonics occuring in the lathe while hollowing. Check to make sure the lathe still firmly attached to the cabinet, and make sure the 4 feet of the cabinet are still firmly on the floor. Mine was due to one of the four legs creeped up on me and wasn't fully supporting it's fair share of weight. It's just a thought... it solved my problem. You would be surprised what little it takes to make a 700+ lb lathe oscillate like you describe.