Thread: Confused

1st question: you can leave either a groove on the inside to expand your chuck jaws into or leave a stub inside to grip. The second is a bit more flexible as far as jaw sizes go.

2nd: don't bother sealing a burl.

Any case, sealer does let some moisture through and for normal rough turned bowls just seal the end grain.

Leave a shallow hole in the bottom to take a scroll chuck to true up the top and finish inside. Rechuck it in a Cole jaw or jam chuck to finish the bottom.
End sealer will allow slow down moisture loss and reduce the risk of cracking. Instead of using end sealer, bury it in a box of shavings. Check the weight each week. When the weight remains steady, finish it off.

Jim

Personally, to finish the bottoms of bowls I use a pair of home-made Cole Jaws. (see: Turning the bottom of the bowl? Help please) They do not hold very firmly, a slight catch can see your piece flying across the room, so light cuts with properly sharpened tools are the order of the day. I also like to bring up the tailstock for extra support (except when I'm finishing the very centre of the bottom... which is the absolute last thing I do!) only, instead of using a live centre I use a Jacob's Chuck with a bit of dowel. This gives me more room to work around the base and although it does tend to "char" a bit, it's easily cleaned up.

Before I made my Cole Jaws, I used to mount a scrap piece on a face plate and turn it to a profile that'd fit fairly loosely inside the bowl. I'd then stick some adhesive foam onto this form, mainly to prevent marking the inside of the bowl but also to provide some grip, then slide the bowl onto this and use the same tailstock method as for the Cole Jaws to hold it all together. Worked for me!

Powderpost is spot on with the info about end-sealer. It's purpose is simply to slow down the drying rate, too fast and the timber splits and warps badly. I guess "sealer" is a bit of a misnomer.

For final cuts on the bottom:
Attach a piece of plywood to a faceplate. Turn to make flat. Turn a groove to mate with the inside edge of the bowl. Somewhat tricky to get exact; you may need to shim with short pieces of duct tape or whatever on the inside of the bowl. Put the bowl on the faceplate, temporarily held in position with the tailstock. Wrap duct tape around the bowl to reach the back of the faceplate, three or four locations. For added security, staple the tape to the back of the faceplate, but I usually don't need this.

Cole jaws or donut chuck also work if you have them.

[Vacuum chuck, too, as long as the wood isn't porous or has through-wall voids.]

Joe

For end-stock support I used the live centre but put a plastic hose fitting over the cone - the part that screws onto your garden tap to take a female click fitting. To avoid marking I add a soft disc of leather or similar. This setup gives another inch or so of clearance.

Thanks guys, just turned my first green burl, what a joy after only doing dry stuff, much easier. Went to about an inch Thick, put end sealer on and buried it in the shavings in a box. Think i might try and make a set a Cole jaws, doesn't look that hard with a bit of ply and some rubber door stops.

Cheers.
Benji.

With some of my bowls when I want to finish the bottom I have a piece of MDF (turned round) that I have screwed a stub on the back to hold in the chuck. On the face of the MDF I have heaps of concentric circles that I have drawn on.

I mount the bowl top rim to the MDF, lined up with one of the circles using Blu tak. You need to adjust the positioning sometimes to make sure it's centered but from there on it is easy. Obviously you need to only use fine cuts and use some caution.

One other advantage with this method is that you can have the bowl finished (except the base of course.) and mount it without damaging the finish.

I have found this method easy and reliable. Using care I have not lost any bowls yet! Famous last words I suppose!

Neat idea Wayne.

Double sided carpet tape could also be used if the surfaces are large enough, or hot melt glue.