Distortion Caused By Centrifugal Force?

[Mike Minto]

Often, when taking finish cuts and sanding a bowl, I think its thin walls must be deforming (temporarily) - yes/no? - making finishing problematic. I know bowl steadies exist to help make working such a form easier - but I don't have one for my mini-lathe; what do you guys do?

[Bill Bolen]

That for sure happens Mike. When thin I usually use the fingers on my left hand to support the thin walls while turning. On overly large piecesI made a bowl steady from some glued up plywood in an L shape and attached arms and roller blade wheels. Works like the oneway bowl steady. For NE pieces I finish turn the upper 1/3 of the bowl before removing the solid interior down to the bottom. Once the upper third is turned do not go back to it with a chisel. The flexing of the walls will get you everytime...Bill..

[Reed Gray]

There is always some run out on bowls, especially when turning the inside. There is no mass to support the walls, so the walls can flex. This is because of the different grain orientations and how the wood moves and cuts when going from end grain to side grain. Higher speeds can make this worse. You will get less of this if you turn end grain. This is one reason why when turning the inside of a bowl, you do it in stages, especially if you are turning bigger diameter, and thin. With as many bowls as I turn, a bowl steady would be a waste of time as I would have to adjust it for every bowl I turned. So, kind of like turning thinner spindles, I use my left hand as a steady rest. Apply only as much pressure with your hand as you are applying with the tool, or it will deform the other direction. This is very gentle pressure. Do make sure to round over the rim of the bowl as that edge, if left square will slice you like a small razor saw. This is for finish cuts. When sanding, it is much the same thing. Do turn your lathe speed down for sanding, because if there is any warpage at all, you will skip over the valleys (side grain) and bump off the hills (end grain).

robo hippy