Hi,
Thanks for response. Let me clarify. This happens to me with dry wood only. It also happens when I go back over the profile for a cleaner cut. So the blank starts out perfectly round and little by little I get bounces even when not making a particularly aggressive cut.
OK,
outside and
dry wood.
First, the wood's never really as dry inside as out, so you will normally get a bit of contraction after removing the interior. Fact of life, and usually no more than another turner would notice. It will, however, touch the tool on each endgrain part and pass clear of the long if you check it by hand spinning and holding the tool firmly on the rest. I leave it alone, because it's not really visible.
Second, even on a perfectly circular piece it's easier to cut (or sand) along the grain than cut across, so if the piece is thin enough to recoil a bit (=<3/8), you can cut your way into the same situation as above. You really have to hold the tool without pressing to get it perfectly circular, and that means no steadying on the surface. The scraper guys can do fine, with lightest of touches, though at a cost to the surface left by a gouge. Once again, seldom a factor.
Note that neither of these conditions is even permanent. The bowl will move as it gains or looses moisture throughout its existence. You chase at risk for something which may not exist tomorrow.
If you're caught by excesses in one and two, you sometimes end up with visibly thinner long grain and thicker end. I cheat and use a steady so the walls are of uniform thickness. It also cuts down on chatter from hardness differential and the long/end grain drag difference. Since I sand with a device supported on the toolrest, I can gauge the difference in circularity pretty well, just like the scrapers. It usually isn't there when the rest is employed. Now next week ... 'nother matter.
