Bowl holding options?

[Doug Ladendorf]

Hi all,
Between the cold and snow, trying to insulate my garage and restoring a couple machines I haven't done much woodworking lately. The exception is my son's pinewood derby car, which was fun to do with him and has sparked my desire to start turning again. I have several half rounds that I would like to turn into bowls but haven't done anything with them because I don't have any way to hold the bowl on the final turning of the bottom and foot. I don't have a vacuum chuck, nor is it in the budget right now. I do have a Nova G3 and the cole jaw set but some of the bowls will exceed the capacity. So I'm looking for recommendations of what options I might have. My Delta 1440 has a 14" swing so won't be bigger than that. Any and all input is appreciated.
Thanks
Doug

[Peter Fabricius]

Hi Doug,
You could just open the jaws of your chuck, place a piece of carpet underlay over the jaws and set the bowl on the padding with the live centre holding the bowl in place. This will get your bottom down to just a very small nub that is easy to remove with a chisel and a little sanding with a small sanding disk.
good luck.
Peter F.

[Steve Schlumpf]

Doug, do a Google search for 'donut chuck' and make one. I have a vacuum chuck but still use the donut chuck for a lot of things.

[Thomas Canfield]

My normal procedure is to use a jam chuck (or plate) similar to what Peter said. I have made quite a few out of MDF to fit different size bowls and use the jam chucks with tenon in a chuck or have some threaded to mount direct to drive. I use some of the rubber shelf liner for pad between the sanded inside of the bowl and then have the live center in a dimple left in the original tenon. I can then turn off the tenon down to a small section and sand the bottom. The small section is cut off with a flush cut saw using a plastic protector against the bowl bottom and the little nub then sanded down. That has worked for bowls and pieces up to 20" D. Something similar is done for hollow forms using a shaft with pad to put pressure on the bottom and some support near the top of the hollow form. I also will use my Cole jaws at times or the donut chuck, but those have diameter limits less than the turning limit of my lathe. I do not have a vacuum system, nor plan to get one in the future, but they work well for many.

[Dwight Rutherford]

Here are some options including those mentioned above. http://www.ptwoodturners.org/Tips%20and%20Handouts/Methods%20and%20Jigs%20for%20Reverse%20Turning%20B owls.pdf

[Doug Ladendorf]

Thanks guys, some excellent ideas. I'm reminded that I have a Beall tap for threading wood that I hadn't got to use yet. Do jam chucks need to be on the outside (plate) or would that category include Peter's suggestion of the chuck with carpet overlay, or appropriately shaped wood mount with shelf liner?

Dwight, I had seen John Lucas' PDF a couple years ago but had lost track. Thanks for the link.

Doug

[Dwight Rutherford]

A jam chuck can be an "inie" or an "outie" .

[Brian Tymchak]

Here are some options including those mentioned above. http://www.ptwoodturners.org/Tips%20and%20Handouts/Methods%20and%20Jigs%20for%20Reverse%20Turning%20B owls.pdf

Excellent resource. Thanks for the link.

[Michael Mills]

I typically use a friction chuck similar to what Peter described. The difference is I turned several disc of different diameters.
I just turn the disc between centers and add a tenon or recess for the chuck jaws to grip. I have three diameters and can match the base diameter close enough. The face is either flat or concave so contact is made around the edge giving good support where the heaviest cuts will be made. To cover you can use carpet underlay as Peter suggest, a used mouse pad, scrap leather…. anything that will provide good friction without a lot of pressure from the tailstock.
Unless a bowl is really deep there is plenty of room from the friction chuck end to the headstock. For deep items you may have to glue up several layers of wood to add depth.
When I think of jam chuck I see them the way John Lucas shows in his first pictures. But you have to turn one to fit each bowl.
A friction chuck would be similar to the extension in “Home made adjustable chuck” only mine is held in the chuck jaws. Disc of 3”, 4”, and 5” cover 99% of all needs. Also do not make the end rounded (like the end of a bat) as this provides little friction area and is easy to wobble. If the end is flat or concave it contacts around the circumference giving a firm and wide mating surface.

Another excellent source is Mike Peace’s video on holding methods. Almost everything is covered in the 1.5 hours and is presented very well.

http://www.youtube.com/watch?v=aUXil-5dEeo

[Robert Henrickson]

I use a jam (or friction) chuck for almost everything (plates, bowls, hollow forms) even though I do have a vacuum chuck. I probably have a couple dozen on hand now -- various lengths, diameters, and end profiles (concave to convex) -- left over from specific needs, turned from scrap. I can usually find what I need in the stash quickly, but whatever comes to hand can always be reshaped to need. The majority are concave-ended, with varied diameters and depths of concavity. My usual pad between turning and jam chuck face are disks of foam cut from drink can insulators, but scraps of carpet pad also are good, especially for larger pieces.

[Jeff Gilfor]

+1 for the jam or donut chuck. The jam chuck is easier though.

Also. Once you get the bottom finished down to a small nib, some painters tape will provide sufficient hold to secure the piece to the jam chuck, with slower RPMs, and gentle cuts, to take the last bit off and sand it down.

[Thomas Canfield]

The "innie" jam or friction chuck will work with a natural edge where a "outie" jam or donut chuck will not work. One concern with thin bottoms is the pressure put on unsupported wood and flex of the bottom. I like to get the jam closer to center for the thin pieces or large flat bottoms.

[robert baccus]

These are all good ideas. An easy outie is a 6' wood cone with a tenon rear end in the chuck.. Also a Dowel that will fit into your chuck and 80 grit sandpaper glued to the end is an easy up to a 10-15# blank if well balanced. Add plenty of tailstock pressure.

[Frank Drew]

I packed the head and tailstocks of my Rockwell lathe up to 19" throw, which is beyond the capacity of Cole Jaws. So I extended the reach of the Cole Jaws by adding a larger disk of 5/8" or 3/4" baltic birch cut into four even wedges matching the jaws existing joints and added threaded inserts for fastening the jaw grippers.

[Cut a plywood disk somewhat smaller in diameter than your lathe's throw (my first one was out of 3/4" mdf, and it worked fine); bore a hole in the center of the disk so that it will fit over the Cole Jaws smaller, central jaws; mount the disk on the Cole Jaws, fastening through the existing tapped holes (with appropriately long bolts); true up the perimeter of the disk if necessary; mark concentric rings spaced evenly and about a 1/2" apart out towards the rim, starting about where the Cole Jaws capacity ends; then mark where to cut the disk into 4 pie-shaped wedges, using the joint spaces of the Cole Jaws as guides. Use the Cole Jaws spacing scheme for placing your threaded inserts in the new jaw plates to take the padded grippers. The whole thing takes a couple, two, three hours to make but once it's done you'll have easily placed and removed jaw plates with quick and accurate adjustment to the limits of your machine.]

[John Grace]

While I'm sure someone else has posted this and I've simply missed it, another idea is to make your own set of Cole Jaws out of birch plywood. I saw a YouTube video on it recently and it looks relatively straightforward.

Just another option and thought...good luck.

[Brian Brown]

I described my method in another thread earlier. You can find it here: http://www.sawmillcreek.org/showthread.php?205735-Jam-chuck-versus-Straka-chuck-question (http://www.sawmillcreek.org/showthread.php?214949-Bowl-holding-options) I just used this method again last night for a bowl. I like it because it is fast cheap and secure. I haven't tried to take it off the chuck yet, but I am worried that I used too much glue, and this bowl is thinner than most I turn. I am concerned that it will break when I try to remove it. Good luck.

[robert baccus]

One design feature I insist on for turn-around chucks is that they do not require removing the chuck. There are so many simple and fast methods.

[Doug Ladendorf]

Again, thank you for the insights. I like the idea of an "innie" with a tenon held in the chuck. May try to turn one of those.

Brian, I think you may have grabbed the wrong link?

Doug

[Brian Brown]

Brian, I think you may have grabbed the wrong link?

Doug

Yep! I think it's fixed now.

[robert baccus]

The easiest friction chuck is a piece of pipe(1/2 ID at Lowes) 6" to 16" with a glued on concave wood block on the end. The pipe fits perfectly in the inside jaws of most chucks and provides a strong and straight conection to the chuck. Bring up the tailstock with a 1/4" flat point and turn the bottom. You can do this before you can say colejaws. This fits in the bowl or vase bottom and is very stable. While it's there go ahead and sand/finish the piece and then trim the 1/4" nipple.

[Scott Conners]

I have turned everything from bowls to mostly closed forms using a jam/friction chuck to finish the foot. I typically put a high quality paper towel folded in quarters on my closed chuck jaws and put the inside of the bowl against that. Then I use the live center (sometimes without the center pin) to press against the bottom of the bowl. I turn the foot leaving an inverted cone, and stop when the nub is 1/4" or so. I cut that off and sand it smooth. If my chuck doesn't fit inside the form, I turn a 2" or 3" diameter wood rod held in my chuck and use that against the inside of the bowl.