DIYbanter - View Single Post - Old desk as bench for South Bend 10K lathe

bob prohaska

wrote:
No matter how straight your lathe was when made it will twist some
when set on a surface that is not true. Then, if fastened down, it

This I absolutely agree with.

will deform more. No matter what surface you are going to attach it to
the lathe will need to be leveled in order for it to cut straight. On

Thus my question: "Why fasten it down?" The only reason I can think of
is to help disspate acoustic energy generated by tool chatter, in an
effort to reduce ringing in the bed.

a wood desk it will change over time with temperature and humidity. So
bolt it to the desk top. Adding the 1/2" sheet of plywood won't
increase the stiffness of the mounting unless it is fastened to the
desk top in such a way as to be essentially part of the desk top.
Gluing it down properly would do this. Then the amount of stiffness
will be increased much more because the stifness goes up by the cube
of the thickness. In other words, a benchtop twice as thick is 8 times
as stiff.

Even then, can the benchtop contribute discernibly to the stiffness of
the cast-iron lathe bed? It looks as if the stiffness of iron is about
ten times the stiffness of wood. The table is 2.5" thick at most, the
lathe bed is nearly a box beam 4 by 4 inches, not counting the ways.

There seems to be an inherent Catch-22: If the wood is thick enough to
contribute to stiffness, its warpage will contribute to distortion.

Thanks for your thoughts!

bob prohaska