Thread: Ice hockey puck machine feet (supplier)

Originally Posted by simonl

Hi Pete. A valid point at that. It doesnt take much of anything to loose the fine level adjustment on a lathe. For most work its of little consequence but every now and again you nay want to turn something long and parallel and thats when you realise that your lathe is no longer as level as it was when you last adjusted it.

Simon

Simon, it is not only when making "something long and parallel" that bed twist matters. It is more often when you make something not that long, but need it to be accurate. Imagine yo want to turn something 20mm diameter and 50mm long that needs to be a good fit. And the micrometer shows it to be 0.02mm thicker at one end. Because the 100mm thick concrete floor has moved. Because the soil under it is reactive clay that swells and shrinks with the seasons changing moisture content. What can you do, short of changing home or the concrete floor?

- keep correcting parallelism by adjusting always the same machine foot. This works very well, but requires you to spend time making one or two test cuts to measure taper error whenever you need an accurate part. Harold Hall describes how he does this with a Myford, in "Lathework a complete course" on page 36.

- if it is a smaller bench type lathe, and the bed does not have an inherent twist, do not mount it rigidly. Let instead the bed find its own stress- and twist free position. This is done by a) putting a hard rubber interface between the lathe bed and the table, and b) only bolting down the headstock side, the bolts at the tailstock side are inserted but left loose. Now your lathe is independent from movements in the floor and bench. The downside is, the bench/cabinet is not contributing anymore to the overall stiffness/rigidity of the machine.


With regard to rubber interfaces (puck) on larger machines, the only reason I am aware of these are used, is to reduce vibrations and noise from the machine onto the building floor and from there to other machines that may not like these vibrations.