Hollow Form Reverse Jam Chucks - Which one to buy?

[Glen Blanchard]

I think I'm going to order one of these things and thought I'd check to see if there are any opinions as which one to purchase. I'm leaning towards the Kelton, but can be persuaded. I had decided on Don's offereing but ran across a less than flattering thread here on SMC about shipping, etc.


Craft Supply's Kelton Woodchucker Mandrel - $93.50

http://www.woodturnerscatalog.com/images/prod/275/kel_woo_man.jpg


Rubber Chucky - $84.95

http://www.rubberchucky.com/smallpic.php?reverse%20chucky%20unit.jpg


Don Pencil's Jamchuck - $39.95

http://donpencil.com/images/JC_GOLD.jpg

[Faust M. Ruggiero]

I have the cheap one. It works fine. You have to turn your own cone. I use a 1" sanding pad with a piece of 80 grit on the bottom. Plenty of friction for light cuts.
faust

[Larry Matchett]

I use Don's, very versatile. If I had to do it over I would probably go with the rubber chucky.

[John Keeton]

I made one, but never use it. I just use a wood cone in the chuck with a piece of drawer liner for friction. It works on a variety of form styles.

[Dwight Rutherford]

If you use some all thread ,turn a wooden cone then epoxy a nut into it, a sanding pad at one end, you have one for less than $5.00.

[robert baccus]

I stumbled up on the top pic device years ago. Go buy you some 1/2" plumbing pipe and just play tinkertoys with it. It will chuck up tight in most chucks. Use 2 pieces of pipe and a connection and it can be used for short or long pieces--bowls or deep vases. Sets up in seconds and maybe cost $1.50. Set the cone with pipe clamp of small sizes. Lowe's has pipes already cut to short sizes and threaded--piece of cake.

[Michael Mills]

I do similar to John and use a friction chuck. The Nova live center comes with what they call a threaded insert which has a 2MT which can be taken from the live center and used as a drive center in the headstock. No tapping for thread, just drill a hole for the barrel and hammer in a tee nut. Since the taper on the 2MT is fairly short I use it with smaller items. You can make the center any size/shape you want, on this one I used a firm rubber ball.
Insert in live center and then in headstock.

[Robert Henrickson]

I made one, but never use it. I just use a wood cone in the chuck with a piece of drawer liner for friction. It works on a variety of form styles.

I take the same approach, making my own, though I use domed/rounded profiles rather than conical. I bought the materials for making something like the things illustrated in the original post, for several dollars total, but have yet to find it worth my time (a matter of minutes) to actually assemble the thing, even after doing a couple hundred hollow forms.

[Thom Sturgill]

Glen, All of these require tailstock pressure and presume that the vessel is too weak to bear mild tailstock pressure or that the turner is too ham-fisted and insecure to use light tail-stock pressure.

I have never seen the need, but then again I've never done a form that was mostly air.:eek: Light tailstock pressure, sharp tools and light cuts have always been sufficient. That and remembering to always remove the tenon by reducing its diameter (cutting toward the headstock) rather than reducing its thickness (cutting toward center). Save the radial cuts for v-e-r-y light finishing cuts.

[guy laizure]

I would buy the rubber chucky.I have one and it works great.Customer service is extremely good.

[Glen Blanchard]

I have a vacuum chuck and use it regularly. The reason I am wanting to try a device such as this is for thin stuff that would not likely survive the vacuum. I came close to going home-brew, but ultimately ordered a rubber chucky this afternoon.

[John Spitters]

Just use your vacuum chuck without applying vacuum and bring up the tailstock for support. I've finished the bottoms of a few hundred hollow forms this way, and have a variety of different sized vacuum chucks that I can use.

John

[Glen Blanchard]

Just use your vacuum chuck without applying vacuum and bring up the tailstock for support. I've finished the bottoms of a few hundred hollow forms this way, and have a variety of different sized vacuum chucks that I can use.

John

I question the ability of a thin HF to handle enough tail stock pressure to keep it in place without imploding the darned thing.

[Paul Gilbert]

+1 on the rubber chuckie. I considered the do-it-yourself solution, but the MT2 taper on the shaft has proven to be a great convenience. I also use the base pads on my One Way clone center for things like holding things up against a friction drive. It's a neat solution to a lot of obscure problems that you never knew you had. Highly recommended.

[Thomas Canfield]

I have the Don Pencil (both lengths) and several turned cones that I use along with some rubber shelf liner and a small sanding disk and pad with rubber at end of shaft. The Rubber Chucky looks good but has limited use, and I have made cones up to 12" D to use with some large hollow forms.

[robert baccus]

The device in the first pic gets around the diameter and rim/tailstock pressure problems. I use mine on large bowls and 20" deep vases. The cone has no pressure on it--it's just for keeping a vase straight. Maybe $2.00 homemade.

[Mike Nathal]

I too usually just use a wood cone in the chuck with a piece of drawer liner and tail stock pressure. But I was re-reading Ellsworth's book the other day and he showed using a bowl instead of cone. I tried this on a vase with a ~1 inch opening and like it much better. First, it greatly increases the amount of wood that is bearing the load, as you are going from a 1 inch diameter throat to a 3-5 inch diameter shoulder. Second, it puts the wood in compression rather than tension (the cone is wedging the wood in the throat outward).

[Robert Henrickson]

I too usually just use a wood cone in the chuck with a piece of drawer liner and tail stock pressure. But I was re-reading Ellsworth's book the other day and he showed using a bowl instead of cone. I tried this on a vase with a ~1 inch opening and like it much better. First, it greatly increases the amount of wood that is bearing the load, as you are going from a 1 inch diameter throat to a 3-5 inch diameter shoulder. Second, it puts the wood in compression rather than tension (the cone is wedging the wood in the throat outward).

I took a look at the book. I also have used this method. I have a number of homemade jam chucks of various diameters with concave ends of various depths. They can be used in finishing bowls or plates, in addition to the hollow forms.

[Reed Gray]

On the few hollow forms I do, when I reverse chuck it, I make a recess type chuck, rather than an expansion type one. Don't want to overexpand the opening and split it.

robo hippy

[Thomas Canfield]

One key point is to have the main pressure contact at the foot or end of the jam against the live center, and the cone/bowl or top support just to help prevent bobble. The pad at that point is to protect the surface and should not be a wedge force. The cone gives more flexibility with a smaller piece of wood and also works for a natural or irregular lip on opening. I have to say that I have never tri a "bowl" at top, but it should work well also for most uses.

[John Spitters]

I question the ability of a thin HF to handle enough tail stock pressure to keep it in place without imploding the darned thing.

When you use a vacuum chuck as a jamb chuck ( no different than what Elsworth does with a bowl ) you are holding your hollow form in compression, under compression the form is very strong even with thin walls. Think of this in terms of an egg, perhaps one of natures strongest forms in its simplicity.