Reducing chatter on threaded tubes. Any tips?

mmurray70 · Feb 23, 2021

Hi guys I have some 1.75 OD, 1.5" ID aluminum tube that gets threaded on the outside. Parts vary in length up to about 12" long (threaded about 9"). I install a delrin plug in the end of the tube and support with tailstock.

Struggling a little with chatter right next to tailstock center. Which is strange as the middle looks fine and tailstock is nice and solid. Any suggestions on how to improve it? Something I can put inside the tube to dampen it? Needs to be very easy to install and remove.

I tried making a plug that extended well into the tube, and put bunch of o-rings on it. seemed to actually make it worse. Only thing I can figure is my longer plug was heavier and maybe changed the frequency it vibrated at and made it worse. What if I went to the extreme and make a very heavy plug, solid steel or something? Could this help?

What are some good ideas to dampen this tube? What kind of RPM would you expect to be able to run this setup at?

Delw · Feb 23, 2021

mmurray70 said:
Hi guys I have some 1.75 OD, 1.5" ID aluminum tube that gets threaded on the outside. Parts vary in length up to about 12" long (threaded about 9"). I install a delrin plug in the end of the tube and support with tailstock.

Struggling a little with chatter right next to tailstock center. Which is strange as the middle looks fine and tailstock is nice and solid. Any suggestions on how to improve it? Something I can put inside the tube to dampen it? Needs to be very easy to install and remove.

I tried making a plug that extended well into the tube, and put bunch of o-rings on it. seemed to actually make it worse. Only thing I can figure is my longer plug was heavier and maybe changed the frequency it vibrated at and made it worse. What if I went to the extreme and make a very heavy plug, solid steel or something? Could this help?

What are some good ideas to dampen this tube? What kind of RPM would you expect to be able to run this setup at?

make a piece that will fit in the ID of the tube about .030 diam less. then put 3 to 4 orings in that pcs you made. put some grease on orings and slide it in.
you can even make the piece as an arbor with center hole in it and and od to clamp on.

Delw · Feb 23, 2021

Delw said:
make a piece that will fit in the ID of the tube about .030 diam less. then put 3 to 4 orings in that pcs you made. put some grease on orings and slide it in.
you can even make the piece as an arbor with center hole in it and and od to clamp on.

forgot to add, you need a cap for the center side have that slip fit over the arbor so it press's up against the tube face
so basically you have a arbor with a face that locates on the tube face, then a cap that loacates on the other tube face and center. (squeezes them together so to speak) the orings on the arbor will absorb the chatter.

Scruffy887 · Feb 24, 2021

Can you slit the delrin plug so that it expands under tailstock pressure? Assuming it has a shoulder and would need an inch or 2 in length. Like an expanding collet.

CORONA VIRUS · Feb 24, 2021

Try threading from left to right.

kustomizer · Feb 24, 2021

Roll up some shop towels wet with coolant and shove them inside with a snug fit

mmurray70 · Feb 24, 2021

The plug is pretty tight, cant see that being an issue. And I actually already am threading left to right. This is on an ancient mazak cnc that uses all right side up tooling.

I will try a longer plug that extends all the way to chuck, the tubing flexes so chuck should clamp down on it too.

Also bought some heavy rubber hose, will try cutting some slots in that and letting it expand out against inside of tube.

And finally I bought bunch of steel bearing balls, and some bicycyle tube. Hoping to make a rubber tube filled with steel balls and oil that will expand to fit inside. I just hope the tube is an ok size. Any ideas where i can get specific size thin rubber tube? Cant seem to find anything on mcmaster without belts in it to handle pressure.

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Reducing chatter on threaded tubes. Any tips?

mmurray70

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Delw

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Delw

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Scruffy887

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CORONA VIRUS

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kustomizer

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mmurray70

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