Dumb Jam Chuck Question

[Stan Smith]

I'm turning a small lidded box. the inside depth is about 3 5/8". From what I've seen and read, using a jam chuck seems to be the recommended way to secure and part off the bottom tenon. On my box, that tenon is about 3/8" deep. One recommendation is to make the tenon from the 3/8" tenon left in the chuck. I'm wondering if 3/8" is long enough to be a jam chuck support for the box base. I realize that the tail stock will provide support, but eventually I'll have to clean up the bottom. I guess I could get down to a small piece left and saw off the base from the tenon and clean up the bottom with sand paper/flexcut chisels. I also have sets of those chuck plates with the rubber feet that I could use. I was also wondering about spigot jaws on a chuck. I have those also. I'm using a jet 1221vs. This is my first box except for some treen mandrel boxes. The wood is spalted maple and it's fairly hard. I'm concerned about the project being secure on the lathe. Thanks for any comments.

Stan

[Larry Matchett]

When I do boxes I use the chuck in expansion mode. I stretch a bicycle inner tube over the jaws so they do not leave a mark on the inside of the box. You can do the same thing with the lid although I usually finish the top of the lid by placing it on the lower part of the box and finish it jam style. I usually use the 50mm jaws for small boxes and the 70mm jaws for the larger boxes. I have only done a couple that required my 100mm jaws. I also have 120mm jaws but have not turned a box that big.

[Dennis Ford]

I make a jamb chuck to fit the opening, the only issue with having just 3/8" is that you must get it right before using up the block. With a longer piece for a jamb chuck, you can cut it off and try again if the fit is so sloppy that a paper towel will not fill the gap. Use the tail-stock and clean up the small nib off the lathe.

[Thom Sturgill]

I've used the chuck jaws in expansion mode many times. Yes, you can destroy the box by using too much pressure, but you only need enough to make the box spin. A jamb chuck only exerts a small amount of pressure. This is the one case where the held object SHOULD touch the face of the jaws. Tape, foam, paper towel, bicycle inner tube, or whatever is handy can be used to protect the inside of the box from being marked by the chuck.

I have also used the top, hollowed and fit, but not shaped on the outside, as a jamb chuck and then used soft jaws either to hold the box while I used it as a jamb to shape the top or to hold the top itself while I shaped the outside of the top.

In the future, plan a little extra on vessels and save the part with the tenon when you part off the project. They are way useful for jamb chucks and glue blocks.

[Bruce Pratt]

If you are concerned about splitting the box when using the jaws in expansion mode, tightly wrap the outside of the box with duct tape or strapping tape. If the wood is soft enough so that the tape adhesive will lift fibers when it is removed, first wrap the outside of the box with paper or plastic wrap and the over-wrap with the tape.

[robert baccus]

Can you cheat and just grab, with the chuck, one half of the 3/8 tenon with the tailstock(padded) holding pressure and remove the tenon with a thin parting tool? Lidded boxes are brain twisters.

[Thomas Canfield]

I make a jamb chuck to fit the opening, the only issue with having just 3/8" is that you must get it right before using up the block. With a longer piece for a jamb chuck, you can cut it off and try again if the fit is so sloppy that a paper towel will not fill the gap. Use the tail-stock and clean up the small nib off the lathe.

I agree but will add that you can often add some "blue masking tape" to help hold the piece to the jamb block, but still use the live center to apply pressure for doing the majority of bottom clean up, and only remove live center for a small center nub.

[Stan Smith]

Wow! Thanks everyone for all the great suggestions. Right now I have my Vicmarc 100 on the lathe. I do have spigot jaws for it and I'll check to see if they'll work after I'm through hollowing out the box. If I use a jam chuck, I can always make one out of a scrap piece that will be long enough. I've noticed that every time I start changing things around, I always have to bring the project back into round. I do have some non-pointed tips for the live center that I'm thinking of using to help hold the top on the base while I shape the top. I might have to use a tissue between the top and base, too. My fit is a little on the loose side due to me not paying close enough attention, Duh!

I've been using my Harrison round carbide tool, rounded scraper, and Berger tool for the hollowing and that seems to be working fine. I did drill a 1/2" hole to make sure I didn't go too deep inside. Again, mega thanks to all!!!

Stan

[robert baccus]

If using the oneway live center you can use the big cone( reversed and padded) on the box top--takes almost any shape.

[Kyle Iwamoto]

I've noticed that every time I start changing things around, I always have to bring the project back into round.

Mark the tenon on both sides of the #1 jaw (or any that you prefer). That way every time you put the piece back, you will mount it in the same place. Makes re-turning much easier.

For a jam chuck, 3/8 is plenty. Remember that when you cut without the tailstock, you cannot cut toward the center of the lathe, always cut toward the headstock.

[Stan Smith]

Thanks for that very useful info Kyle. I had not heard either of those before.

Have you been able to dodge the storms? We were in Kauai in May and the chickens are everywhere as a result of a past storm. They are a strong memory of our trip there. We even bought a glass rooster as a souvenir. :)

[Kyle Iwamoto]

Well, the hurricane dodged us. Thankfully, at the last minute, she decided to turn away from the islands. The chickens on Kauai is the result of hurricane Iniki. Most of those are escaped imported fighting chickens. They are quite prevalent now. Pretty soon they will be known as the "Chicken" isle vice the "Garden" isle. I was sweating this hurricane, I think it was following the same track as Iniki did.

[Stan Smith]

Glad to hear it passed you by, Kyle.

I just had a neat experience. I have the lid on and taped to the base. The lid still had the tenon on and it was time to turn it off. I got down to just a small tenon and decided to try my small Easy Wood detail tool. It really works well to clean up the top end grain and nibs. I used a very delicate touch after removing the tail stock and it looked like I had sanded when I was done. Yes, I know that other tools can do the same--if you are proficient with them. I didn't want to mess up the top or have it come loose either. I guess some of that "chicken" stuff rubbed off on me when I was in Kauai because when I got down to a 1/4", I turned the lathe off and reached for my fine tooth dozuki saw. The EWT small detailer cleaned up the nib just fine.

I remembered that I had a live center set that had some non-pointed tips so I put one of those on. It's sort of a cheapo set that I've had for a lot of years, but never used it very often. Glad that I still have it. This is continuing to be quite the learning experience for me. Boxes involve more steps than I thought. Again, thanks to all for your advice.

Stan

[Thomas Canfield]

Glad to hear it passed you by, Kyle.


I remembered that I had a live center set that had some non-pointed tips so I put one of those on. It's sort of a cheapo set that I've had for a lot of years, but never used it very often. Glad that I still have it. This is continuing to be quite the learning experience for me. Boxes involve more steps than I thought. Again, thanks to all for your advice.

Stan

Stan - It looks like you made a very valid statement. Some of the items we purchased early on still seem to have some purpose later, and often not for what they were purchased. We do build on our experiences, both good and bad. Keep at it.

[Stan Smith]

Thanks, Thomas.

[Stan Smith]

Looks like the most common way to mount the base, to clean up the bottom, is to turn and fit a jam chuck. I can also use a chuck with spigot jaws. I just remembered that I have a set of rubber expandable jam chucks. The largest size of 2" fits the inside perfectly and is slightly tight without even using the expansion nut. The expandable jam chuck would have to be mounted in my drill chuck. I could also use my talon chuck with spigot jaws. So, this is where I get confused about which is the best way to go when all would work. I will be using the tail stock for support until the very last little bit of clean up. Just wondering if there are any more suggestions. Thanks.

[Stan Smith]

Guess there were no more suggestions. I used my Talon chuck with spigot jaws. Worked quite well. I chose this method thinking that there would be the least amount of wobble or out-of-round issues. There were neither. The spigot jaws have ridges so I was a little worried about them ruining the inside finish, but that was minor. I did use the tailstock with a non-pointed live center. I cut a small piece of the shelf cloth and it worked well also. The main mistake I made was in not making the bottom slightly concave. Duh! It was easy to remount it, turn, and re-sand.

I'm going to be making a communion goblet for our church so many of your suggestions will apply to that as well. I was wondering about the goblet design, but a Google search came up with a lot of pictures to choose from. I really appreciate all of your suggestions and comments. Thanks so much!

Stan