A lot of workholding for CNC routers involves putting a downward force on the stock material in order to keep it in place. Vacuum tables, pressure feet, even clamps (with much larger force than the other two). But this normal force is only one of the two factors in the equation. The other factor is the coefficient of static friction between your stock material and the material of the spoilboard. So, has anybody done any experiments on different spoilboard materials to see which ones might have a high coefficient of static friction with which stock materials? Picking the right material for a spoilboard or spoilboard coating could greatly increase the effectiveness of workholding. -Jonathon Duerig
I don't have a problem with a big sheet of stock moving during a cut because I clamp it securely at one end. But I do have minor defects when cutting out small pieces with my pressure foot from time to time. Often enough that I have to inspect each one to make sure it is good. For small pieces, I don't use tabs and instead use a pressure foot. The pressure foot would be more effective if my spoilboard had more friction. -D
tried printer paper? I use it when clamping steel parts in the lathe. the paper is coated with clay particles AFAIK, gives very high friction under pressure
