Finish Turning bowls - how to recenter?

[Scott Hackler]

I been thinking about your "wobble" comment. Just wanted to check on something. Are you mating the shoulder on the top of the chuck jaws or bottoming the tenon inside the chuck?? The first is the proper method and the latter WILL cause problems. Just checking.

[Prashun Patel]

Yes, I snug up the shoulder. On my next bowl, I'll double check the shoulder.

[Faust M. Ruggiero]

This may sound complicated but here goes. I make a center dent on the inside of my rough outs as well as the outside. Here's why. Some bowls, especially larger bowls, shrink across the grain a lot. I mount my rough outs with the inside against a jam chuck (actually, one of my vacuum chucks without vacuum) and jam it with the tail center. Since the bowl is way out of round, the inside of the rough out will only contact the jam chuck in two opposing spots in long grain. The jam chuck can act as a wedge and the force of the tail stock against it could crack the rough out. Sooooo, to correct this situation, I mount the bowl with the tenon inside the jam chuck and mount a morse taper extension between the tail stock and the live center and let the tail stock make contact with the inside of the bowl on the indent I left. The extension gives me room to reach inside the bowl. Then I true the inside of the bowl just in the area it will contact the jam chuck, dismount it and turn it around and true the tenon. In this manner, the bowl will fit so securely against the jam chuck you will be able to apply enough pressure with the tail stock to completely turn the outside of the bowl. When you are done, mount it in the chuck and finish the inside. This wasn't something I imagined up, a friend of mine with a lot of experience was kind enough to teach me.
faust

[Mark Levitski]

Prashun, just keep it simple as does Bernie--just jamb it up against the chuck and return the tenon to round (be sure to leave enough diameter when you green turn to allow for the piece to still fit in the jaws after re-turning), flip the tenon into the chuck, and finish. When you rough (green) turn the tenon, sure, I would definitely turn the outside too but expect some adjustment when you reverse it to go into the chuck. It's all a gradual process turning to dry and round. To finally finish the bottom is not critical, but centering helps to minimize the transition from turning to sanding in order to blend the finished base into the finished top.

Mark

[Thomas Canfield]

Also ditto what Bernie said. I open my chuck jaws up wide to get the largest contact, and then jam with the live center in a divot or center left intentionally in the tenon when turned green. I mounted a 16+ D piece this way over the weekend. Make sure you maintain pressure on the live center since some wood may give some during the returning.

[skott nielsen]

I thought it would be best to finish turn the outside at the same time one trues the tenon as this way you are turning towards the headstock and can use a push cut almost the entire way. I must admit I frequently have issues when I reverse to do the inside. Yet I find it difficult to get the cleanest of cuts with a pull cut.

[Faust M. Ruggiero]

Skott,
Practice working left handed. Then your push cuts will be pull cuts. It often pays to be a bit ambidextrous at the lathe.
faust

[Steve Harder]

You guys seem to only true up the tenon before flipping to the scroll chuck. Then you turn the inside AND the outside with the opening facing the tail, correct?

Yes. I true just the tenon and small area surrounding it. Then reverse into chuck and turn inside and outside. Then reverse onto vac chuck, or faceplate with duct tape and turn off tenon. Or to remove tenon, pinch between jam chuck in chuck and live center in tailstock, turn away as much tenon as possible, remove to workbench and remove final bit of tenon with Japanese saw and sand away residual.

I like the reverse onto vac and also have very good luck reversing onto very large foam padded faceplate and secure with duct tape or fiber tape.

[Ken Whitney]

I'm thinking I need another chuck that I can mount in the tailstock

I do occasionally use a tailstock adapter (1 1/4 x 8 on a #2 MT) to reverse-mount the scroll chuck (with the bowl attached) to align it with the vacuum chuck for turning the foot, etc.

But for the initial returning, I do what Bernie does.

[Mark Levitski]

Definitely what Steve H. said: After truing the tenon and at the same time re-turning the outside, you will still need to "re-re-turn" the outside after putting the newly trued tenon into the chuck. One is then using the gouge from the headstock side (tight sometimes, yes). However, when you learn some pull cuts it is no problem at all, and of course as suggested some lefty turning for push cuts can happen at a certain distance from the headstock. I use a pull shear cut with the gouge almost vertical. This leaves the cutting edge on a gouge with wings at a 45-50 degree angle. With light cuts one can shape and take out any ridges. You can rotate the axis from a scraper cut to a peeling cut. Because of the cutting edge angle, catches are rare and not so scary.