powermatic 3520 question

Re: powermatic 3520 question

Gary in Zirconia,NC

>There is a place to put a 2X12 between the legs. The dementions are 48 7/8 X 11 3/4. You could make it bigger since the legs are wider then that, but that is the space for the base.

Re: powermatic 3520 question

Philip Duffy

>Ken, Suggest you wait on any decision re the leg area. After using my 2035 for two years I loaded up the storage box I had there with 300 # of sand. Makes a great improvement in stability and vibration reduction. Phil

Re: powermatic 3520 question

John Lucas

>Ken

I would wait also. You may find you don't want it as tall or in my case I'm going to build the box so it hangs down a little. I also like having my hips close to the bed of the lathe so I will probably build my box a little off center so I can stand very close to the bed. For now I have 300 lbs of gravel stacked on a board across the bed.

Re: powermatic 3520 question

John, Ohio

>I also would wait. I have 300 pounds of sand on a shelf plus left room on top of the sand for another shelf that holds my chucks, and tail centers etc.

Re: powermatic 3520 question

ken chase

>Phil:

I thought the powermatic was heavy enouth not to require the extra weight. Would you suggest bolting it to the floor? And, if so, what is the best way to do that?

Thanks for the advice. I'll take it and hold off

building storage.

Ken

Re: powermatic 3520 question

John Lucas

>Ken

It depends on what your turning and how fast you like to turn. If you get an off balance piece, even a small one and you spin it fast the lathe will vibrate. The extra weight reduces this. It doesn't walk all over the shop like my last 3 lathes, even without the extra weight.

I've had this problem with wood that is punky on one side. This piece will be unbalanced and cause the lathe to vibrate. It's not a serious problem but you get a cleaner cut when the lathe is rock solid.

Re: powermatic 3520 question

Gary in Zirconia,NC

>It all depends on how much weight you turn. I bolted mine to the floor and it started pulling the bolts out of the anchors. The lathe only weighs 675 lbs. I'd hold off on the tool rack also, as that area will be full of saw dust and chips.

Re: powermatic 3520 question

Chris K in MD

>I didnt put a ballast box on yet as I wantd to make sure that I liked where it is ( I actually moved it once). I have encouneterd a little vibration with unablanced pieces the nice thing is a sliht change in the speed damped it out. Its more of a resonance and the extra mass can change the vibration or a change in speed.

Chris

another vibration option

John K Jordan

>>If you get an off balance piece, even a

>small one and you spin it fast the lathe

>will vibrate. The extra weight reduces this.

There's another option I haven't seen discussed. I know a very good turner who turns large unbalanced pieces on an ancient, relatively lightweight Rockwell/Delta lathe with no ballast weight added. His secret: he clamps the lathe to the wall.

From the geometry/physics, it seems to me that a rigid strut high on the lathe near the headstock (and perpendicular to the axis of rotation, of course) could reduce vibration far more than adding weight down low on the lathe stand.

I believe he fastens the tailstock end to the wall as well. This is essence makes his lathe "weigh" thousands of pounds and the only vibration from out-of-balance spinning would be from any flexing of the steel and cast iron in the lathe itself.

JKJ in East TN

JKJ......

W.C. Turner

>"he clamps lathe to wall"

John,

What does he use for clamps?

W.C.

Re: JKJ......

John K Jordan

>>What does he use for clamps?

In his old shop I think it was 2x4's clamped with C-clamps. I don't think it would matter what kind of clamps or what kind of strut as long as it was strong enough. If the lathe was in a permanent location, wood or steel angle iron could even be fastened to both the lathe and the wall with bolts.

From a structural design point of view (and if the lathe was not too close to the wall), better than a horizontal strut would be a diagonal strut fastened from the top of the lathe to a point near the floor. This would keep the wall itself from flexing from large forces if the wall was not sufficiently rigid. (You can imagine how a large out-of-balance piece could shake the sheetrock off a long wall made from 2x4 studs on 24" centers!)

Even better would be a big "X" - a truss arrangement with 3 or 4 struts: a horizontal strut from the top of the lathe to the wall, a diagonal strut from the top of the lathe to the bottom of the wall, another diagonal from the bottom of the lathe to meet the horizontal strut at the wall, and either a second horizontal member along the floor and/or the lathe bolted to the floor.

I've always thought that a nice permanent installation would be a large torsion box fastened to the floor and/or the wall. The top of the box would be a plywood "shelf" between the lathe and the wall. This would also be easy to clean up and keep things from falling behind the lathe. (I'm always dropping that piece of sand paper or wrench) The interior of the box could provide needed storage. The entire thing would keep the lathe very rigid.

It would also be best to provide some means to dampen the vibrations. If the entire thing is TOO rigid, higher forces will be applied to the lathe bearings and other components in the lathe. I can imagine how this could cause catastrophic mechanical failure, especially in a cheaper lathe with a smaller spindle. Designs for dealing with large vibrations usually incorporate dampers made from springs, rubber blocks, hydraulic cylinders, etc. Look at the motor mounts in any automobile. If the engine were mounted rigidly to the car, it might eventually tear the bolts from the frame.

It would be nice if a mechanical engineer took a look at this problem and designed the ultimate support.

JKJ in East TN