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Lathe shaking

Ray Sprouse

Ray Sprouse

Joined
Jun 27, 2017
Messages
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Location
Gaines, Pennsylvania
I am having a terrible time with vibration and shaking with my lathe. I’ve had it for nearly 10 years and haven’t had any issues with vibration or shaking until now. It used to stand on a concrete slab. I built a new 2 story garage. My workshop is on the second floor. I bolted my Powermatic 3520 to the floor, added diagonal supports from floor joist to floor joist, and added 3 4x4 posts from joists to the concrete floor. With all this added, my lathe still wobbles and shakes like crazy when I’m turning unbalanced bowls.

The floor joists are engineered joists that are 18”. My plan is to add plywood to both sides of the joists that are under my lathe because I think they may be flexing harmonically. Next, I plan on pouring a concrete pad on top of the ¾” tongue and groove plywood, about 10’ square and then bolting my lathe through the concrete and floor. Since the lathe is bolted to the ¾” plywood, I am thinking that the plywood is also flexing.

Would these two additions help to decrease the shaking and vibrations? Any other ideas that might help?
 
The best solution I found, was to brace the head stock against horizontal movement.
I bolted several steel 2x2s to the bed, near the headstock. These run back to the wall.
Threaded rods run through those vertically down to the floor.

I built a small form around the rods, from the floor up to the 2x2s and filled it with concrete, it doesn't take a lot, 3 bags if remember correctly.

That stopped all rocking on mine, for even very large unbalanced pieces.

What it really does is provide massive bracing, and widens the stance.

In your scenario, you may have a remaining issue of the joists flexing, allowing vertical movement or your attachments not getting good grip. On other machines, ive drilled drilled right through the the floor/ceiling and run threaded rod to the other side, the torqued it down, using large washers.

Hope that helps
 
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the other alternative is to make the footprint larger. My friend who turned really out of balance pieces on purpose bolted 1/2" thick x 3" angle iron to the feet of his 3520 so he had a foot print of 6 feet. He did have the top part of the angle iron cut off on the tailstock inboard side so that he wouldn't trip over it when walking up to the lathe. Made an unbelievable difference but he was on a concrete floor. Still I think with extra bracing under the floor and a larger foot print you could reduce the vibration tremendously.
 
Ray Sprouse said:
I built a new 2 story garage. My workshop is on the second floor.
Click to expand...

This could be part of the problem. No matter how secure the lathe is to the floor, the fact that your shop is on the upper floor, could mean you will probably always have some amount of shake. The entire building may be moving with the out of balance at the lathe.

-----odie-----
 
Regardless whether a turner is experienced, has razor sharp tools, has perfect presentation and technique......if there is vibration at all, it will be impossible to have as clean a cut as is possible without the vibration. Sometimes vibration can be reduced further, but the turner goes with it, thinking he can sand out any imperfections.....which is true, but sanding always compromises geometric perfection. Any compromise on that, and the details are never as aesthetically appealing as they would have been without the compromises.

-----odie-----
 
Go back to the basics of construction, your foundation is number one.
Moving your rotating mass to the 2nd floor of a wood structure is a problem.
The wood structure will never be rigid enough to absorb the out of balance loads caused by the lathe.
The mass of the structure and rigidity of the structure are two critical elements in overcoming this problem.
We have a number of large rotating equipment on steel reinforced floors in a steel structure and encountered
problems with harmonic shaking of the building. Adding a concrete slab to your 2nd floor could possibly add
to the problem. Adding the concrete slab to 2nd floor could exacerbate the problem with large blanks.
 
The floor joists are the problem. You can stand in the middle of any room on a second floor and do a little heel bounce, and the floor will move. Either move the lathe down stairs, or put 4 by 4 posts under where the feet are, and they need to brace directly off the foundation or a pony wall under the floor...

robo hippy
 
My house bounces when my 27lb dog walks across the room. I guess it's the perfect rhythm they have because it seems to pick up the vibration after she walks about 5 feet and then it get louder.
 
I have felt vibration in a second floor of a concrete structure may be correct in that the problem is from the structure itself and adding weight may only increase it. If you can add posts to first floor as Reed suggested that may be the best solution. But I see you added 4x4 posts already but only 3. So maybe the posts should be 4 and placed under feet of lathe plus the angle John talked of may be as close as you can get with out restructuring the entire floor with joists closer together,
 
odie said:
This could be part of the problem. No matter how secure the lathe is to the floor, the fact that your shop is on the upper floor, could mean you will probably always have some amount of shake. The entire building may be moving with the out of balance at the lathe.
Click to expand...

I agree. You didn't say what the span of the floor joists, but being over a garage I imagine it's in the neighborhood of twenty feet. The problem isn't just the floor directly beneath the lathe, but the entire floor is flexing up and down somewhat like a trampoline. You could put plywood on both top and bottom sides of the joists and it would stiffen the floor, but the problem won't be completely eliminated. I seriously doubt that you will find a satisfactory solution with the lathe on the second floor.

Mike Johnson said:
... Adding a concrete slab to your 2nd floor could possibly add to the problem....
Click to expand...

I agree and can't imagine anything but even greater problems if you pour a slab on the second floor it might lower the resonant frequency of the floor, but the downside of that is the amplitude of vibrations might increase.

robo hippy said:
The floor joists are the problem. You can stand in the middle of any room on a second floor and do a little heel bounce, and the floor will move. Either move the lathe down stairs, or put 4 by 4 posts under where the feet are, and they need to brace directly off the foundation or a pony wall under the floor...

robo hippy
Click to expand...

If that doesn't interfere with parking a car, the posts might help, but I would go with 8X8 posts cross braced and enclosed in plywood. Even better, move the lathe downstairs and park the car outside. A two story shop would be my dream, but no heavy machinery upstairs.
 
Would it be possible to move the lathe to one side of the room where you could provide
solid bracing from the floor below? You could easily box in a support using the existing
outside wall and make a small storage room or closet down below. This would help in
reducing the bounce of the large unsupported upper floor span.
 
odie said:
This could be part of the problem. No matter how secure the lathe is to the floor, the fact that your shop is on the upper floor, could mean you will probably always have some amount of shake. The entire building may be moving with the out of balance at the lathe.

-----odie-----
Click to expand...

Late to the party. Odie is correct. The building is moving with the shaking of the lathe. The shaking is setting up sympathetic vibrations that almost everything is picking up on.
There are two things you can do that will help if you must keep the lathe on the second floor.
1. Isolate the lathe from the floor. Make alternating layers of hard rubber and lead sheets - a triple + decker sandwich under the legs. Bolt the sandwich to the legs but don't bolt the lathe down to the floor or let any metal come in contact with the floor. Make as big as you can afford for each foot of the legs.

2. Make a metal faceplate for the outboard side shaft. Use magnets to coiunter balance the off-center weight of the piece being turned. Position the magnets around the faceplate until the piece spins freely by hand. These need to be serious well-holding magnets that will stay in position under the rpm's you're turning at. That alone could solve the majority of your problem.
 
I have mounted a very unbalanced mixer (that is the way it had to be designed) that shook the table it was mounted on, on a rubber sheet from McMaster Carr. At that point you could write on the table as the mixer was working.

In another case I told a friend who had mounted an old printing press on the second floor of of a very old building that was shaking, with the press in use, to use the same type of rubber. It stopped the transmission to the building.

I forgot which type of rubber I used but go to <http://www.mcmaster.com/> and look for rubber sheets or vibration mounts.

In both cases there was no need to stick a sharp piece of steel into the shaking machine as you stood on the stable floor,

As for magnets, they will move. If static balance is desired use counterweights bolted to the face plate. This will not give dynamic balance only static balance. Think of the the machine used to balance the tires and wheels on your car. In addition as you remove wood the static balance will change and the weights will have to be moved.

Put the lathe downstairs or in a basement.

<It used to stand on a concrete slab. I built a new 2 story garage.>

Use the old garage.

Stu
 
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My lathe is in a portable 12x16 building. It's elevated and on skids. I've turned some large out of balance blanks before and really not had a problem turning. If I turn the speed up and the lathe starts vibrating then I turn the speed down so it doesn't...lol
Really not sure why this is being over thought! Is it imperative to have the speed up where it vibrates that bad?
 
stu senator said:
As for magnets, they will move. If static balance is desired use counterweights bolted to the face plate. This will not give dynamic balance only static balance. Think of the the machine used to balance the tires and wheels on your car. In addition as you remove wood the static balance will change and the weights will have to be moved.
Stu
Click to expand...

As long as the magnets are strong enough and the RPM's aren't too high, the magnets will hold. If counter-weights are bolted, it would be a pain to move them. Magnets are easier to re-position as the wood changes from turning. Relatively soon the turning should level out. Keeping the object below "walking" speed would be an obvious solution as the previous poster pointed out.

Another simple solution would be to use live tooling in the form of a router or lancelot with fractional rpm's. Any form can be created by turning a hand wheel and shaping with a jig-held router. I use an automated system with a robotic arm, but years ago I used simple jigs.

As for a dynamic system, I refer you to this video on Centramatic wheel balancing systems.
Observe that in the demo, he uses a magnet to throw a wheel off balance and it does not move the way it is placed. A Cenramatic wheel balancer would be an elegant solution to any lathe imbalance issue. These are readily available in different sizes.
Mark

View: https://m.youtube.com/watch?v=ullnFQD4F1I
 
Mark Lindquist said:
As for a dynamic system, I refer you to this video on Centramatic wheel balancing systems.
Observe that in the demo, he uses a magnet to throw a wheel off balance and it does not move the way it is placed. A Cenramatic wheel balancer would be an elegant solution to any lathe imbalance issue.
View: https://m.youtube.com/watch?v=ullnFQD4F1I
Click to expand...

This is very interesting idea that I will have to try out
Especially since the largest one is only $200

I like doing off centre pieces and my main focus had been building the strongest, heaviest lathe.

Thanks!
 
Hi Ray. I had a few additional thoughts to what has already been said.

1. Engineered floor joists are very strong but also prone to deflection (felt as bounce.) You put some big ones in there for sure, but it might be worth calling the manufacturer and seeing if they have any ideas. As a retired contractor, I never put in engineered floor joists. I'm old school, and don't like the feel when I walk on them, even on seriously oversized joists, but I'm very sensitive to that sort of thing being a builder for a couple decades. I've been through some training with manufacturers that talked at great length about deflection. There are ways to minimize it, but usually we think about people walking or occasionally a group dancing...not a heavy piece of machinery at moderately high RPMS.

2. Your wall sheathing could also be contributing. I'm more of a plywood than OSB fan, and it's possible that your wall sheathing wasn't fastened as well as it could be. In short, you could also be getting side to side sway in addition to floor vibration/shaking/oscillation. An engineer might also recommend sheathing the interior downstairs of your garage with plywood, though you surely already put drywall on.

3. I've sure seen many a stubborn building case solved quickly by a very astute structural engineer. I've been lucky to work a little with one engineer who is surely a genius. I would recommend starting in the building trades and ask real world builders who they really respect as a structural engineer.

4. You might try raising your 4X posts a little to pre-load the floor in reverse. I don't know exactly how they're attached top and bottom, but there are some elegant metal brackets built to adjust for log home settling.

I personally think it must be possible to have a rock solid lathe on the second floor, it just presents an added challenge. And don't give up on the concrete idea—I just think you need to have either a professional opinion or be willing to try several different options. On the other hand, it may be more work and/or trial and error than it's worth to make room downstairs.
 
I had a chat yesterday with the folks at King Arthur's Tools (manufacturer of Lancleot). They have several lathes on the second floor of their wood-framed building. The structure is very stout, but most important, I think, the lathes are near the walls and more or less perpendicular to the walls. They also advise placing a rock box on a lower shelf for ballast.

Before investing in a dynamic apparatus, I'd want to try a variation on a so-called "tuned mass damper," used on tall buildings prone to earthquakes and lateral wind forces. I envision a box of weights suspended by chains from the lathe bed, to be "tuned" by varying the amount of weight.
 
Joe Greiner said:
Before investing in a dynamic apparatus, I'd want to try a variation on a so-called "tuned mass damper," used on tall buildings prone to earthquakes and lateral wind forces. I envision a box of weights suspended by chains from the lathe bed, to be "tuned" by varying the amount of weight.
Click to expand...

Joe,

I'm interested in the results (& pics) of what you find. Maybe even some before and after videos.

Rich
 
On my bucket list for now, Rich.

Presently, I have about 100 pounds of railroad spike in a tray on a bottom shelf. For seriously unbalanced pieces, I use a Lancelot in a support contraption to trim them, rotating the work by hand.
 

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I see that this thread is several years old but I wonder if anyone has ever tried a Centramatic Balancer? I contacted the company (which is based in Alvarado, TX) and got some info that might be of interest:
1. The smallest OD that Centramatic makes in ±9" made for motorcycles.
2. The hole pattern in central disk can be customized.
3. The balancers are designed to "kick in" about 20 MPH. One can observe in the video above that some threshold of angular momentum has to be reached before the balancer becomes effective.
4. RPM should not be an issue. A 9" diameter rotating 750 RPM is about 20 MPH circumference speed (if I did the math right).
5. The smaller balancers are designed for a "3 oz." imbalance. I don't know what that means in terms of wood imbalance but may be a limitation.
6. Mounting the balancer could be an issue particularly for lathes where the motor is on the outboard side of the headstock (as opposed to underneath). While I don't have an exact dimension, the central disk of the balancer is thin so it might have to be mounted to a faceplate for stability.
Since I like to do multi-axes turning, I will probably try one of these if I can work out a few more details.
 
It looks like the original poster has not been here since he started this thread in 2017. I hope everything turned out okay for him.

He did not tell us anything about his garage other than it is 2-stories and used an 18" tall floor joist. That's not sawn lumber, and likely not a wood I-joist at that height. That leaves open web wood trusses. Light-frame conventional construction (likely his garage) is nothing more than pivot points restrained by small mechanical fasteners. The forces placed upon the building by his lathe exceeded the capacity of the building to resist those forces.

We don't know enough to provide a viable fix: truss span, max. designed truss deflection, on-center spacing of the trusses, bracing requirements from the truss designer, live load design of the trusses, was the concentrated load of the lathe (lathe, its operator, tools, wood, misc.) built into the design of the floor system, and on and on. Tossing all the suggestions at him as they were, those were nothing more than guesses that may or may not have offered some help to the situation.

My professional advice* to this 7-year-old request would have been to hire a licensed structural engineer who specializes in these sorts of situations (dynamic loads against a building- very little difference here to earthquake resistance), or get the lathe down onto the ground floor on the concrete slab. My guess is that an engineer would have created a structure very different from the garden variety conventional construction that was likely used.

Other than this, I think is worst move was to mechanically attach the lathe to the floor. If the attachment were to the 3/4" plywood only, it will flex no matter what. The floor system, trusses and plywood, were probably spec'ed for uniform loading of 40psf, and he had a really big concentrated load at the lathe location. If he bolted it directly to the top cord of the trusses (2x4s laying flat and connected with sheet metal gusset plates), he's asking the truss to resist forces it was not designed for, and very likely violated the truss manufacturer's design requirements. In retrospect, I bet unbolting the lathe from the floor, along with the mods he made (but no concrete, that's way too much weight on the trusses) in the original message, may have provided 'some' relief.

(*I work as a building inspector.)
 
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