Lathe vibration problems can be fixed by adding mass to the lathe. But this page shows how to get the most out of (the least amount of) mass.
Does your lathe vibrate when you turn an out of round piece? Does it jiggle and dance without music when you want a smoothe cut? Do you have to balance your work with sacrificial weights, or have to chain saw pieces off the work to make the lathe behave? Well here is an idea to overcome these problems without adding several tons of sand to the lathe base or building a massive base to bolt the lathe to. And no you do not have to bolt the lathe to the re-inforced concrete floor of Fort Knox.
Try this simple experiment. Take a brick. Shake the brick back and forth. Easy? Yes. Now hold the brick over your head and shake it. Not quite as easy? Now put the brick on a pole and try to shake it while it is higher up still. Get the idea?
Here is my solution. I made a solid steel tube about two feet long and bolted it to the lathe as near to the headstock as possible. On my lathe there is a piece of lathe bed that sticks out to the left of the headstock, the outboard bed, which I never use. The pole sits on this. On top of the pole is a weight in the form of a bucket of sand. The lathe does not wobble or vibrate since the base is sitting on the floor and the weight on the top is multiplied by the lever action of the pole. (The chains were added if I needed extra mass later, and are not holding anything in the picture.)
Math 101, the basic lever. 50 lb of mass at the base of the lathe holds the lathe down but does little to stop vibration since the effective lever action is all in favour of the headstock. As you raise the mass (attached to the lathe) to the headstock the mass becomes more and more effective in dampeneing vibration till it reaches the spindle itself when it is effectively 50 lb of inertial mass. Raise the mass above the spindle and you can multiply the mass by 10 for every 6 5/8 inches above the spindle. This assumes that the mass is solidly attached and that the legs of the lathe are solid to the ground. Six inches above the spindle the 50 lb mass has the dampening effect of 500 lb (50 X 10) and one foot above the spindle it dampens like 1 000 lb (50 X 20). Great eh?
My lathe has to be portable because I like to turn outside, but in Canada that is simply not practical all year. So by adding a 50 lb mass on a two foot pole bolted to the outboard bed I get an effective 1 500 lb dampening mass, since the mass is levered an effective 18 inches above the spindle. This is roughly equivalent to putting 50 X 70 = 3 500 lb of mass 24 inches below the spindle (in the base). Moving that amount of mass would be out of the question of course, but unbolting the fifty pound bucket and then moving the lathe is quite simple.
Remember to contact me if you use this idea and ket me know how it works for you.
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