Rechucking Warped Bowls


Collated from newsgroup postings.


I turned a bowl from green wood to a thickness that was approximately 1/10 the bowl diameter. My question is, once I let it dry, how can I rechuck this bowl since it will no longer be round? I was planning on using my four jaw chuck.


I use a jam chuck and the tail stock. The jam chuck is a piece of cylinder shaped wood, either mounted on a face plate or with a tenon to mount in your 4 jaw chuck (what I use). The length depends on the depth of your bowl but I suspect 5 or 6 inches will suffice. Put a rounded but blunt nose on it. You want the rounded 'shoulder' part to touch the inside diameter of the bowl but not to touch the bottom. I have several jam chucks ranging from about 4" diameter up to about 6 inches diameter. Any kind of wood will work. Place a piece of paper towel on the end of the jam chuck and put the open side of your bowl against that. Bring up the tail stock and put the center point into the original center hole or use your best guess. Tighten the tail stock just enough to keep everything in place. You can now true up the outside of the original tenon and even take some truing cuts on the outside of the bowl if you desire. Remount the bowl in the chuck and finish it.


There are many ways to accomplish remounting. I prefer to retrue the boss by using my chuck in a "Drum Chuck" mode. It is fast, easy and does not require removal of the chuck from the spindle.

With the chuck mounted on the spindle, close the jaws to the smallest diameter. Take the untrue bowl and place it over the closed jaws of the chuck. The jaws should rest in the bottom of the untrue bowl. Bring up your tailstock and centre with the previous centre mark. If you do not have, or did not mark the previous centre (where the tailstock penetrated the bottom of the bowl during roughing), you will need to centre the bowl visually. This may take a few mountings to get the bowl near the correct centre.

With the bowl mounted and the tailstock centre brought up, tighten the tailstock. The bowl will be held by the friction (and pressure) between the chuck jaws, the bowl and the tailstock. You can now bring up the toolrest and return the dovetail (or straight boss) with a small skew chisel. Remember to keep your speed low, whilst retruing the tenon boss. I usually keep the revs around 500 or so during this operation.

Once the boss has been retrued, simply remove the bowl and remount it inside your chuck jaws in the usual manner. I typically take a few light passes on the outer bowl wall, to remove some of the warpage on the outer skin before I remove if from the drum chuck mounting. If the untrue bowl is too deep to mount over the closed jaws of your chuck, you can turn a "stubby" tennon that is long enough to clear the bowl rim. Simply take a wide/deep piece of scrap timber and turn a tenon on it. On the end of the tenon, turn a slight concave. Then, mount your untrue bowl in the same manner as above. The extended tenon acts to hold the inner bowl bottom, whilst you retrue the tenon boss.

Remember, when roughing green bowls... Leave an oversize tenon boss on the roughout, so when you retrue the boss after it has dried, it will still fit your chuck. Another way to remount untrue bowls for retruing the tenon boss, is to turn a dovetail boss on the inside of the bowl when you rough it. Although this will also warp a bit, you can usually get a good enough grip on it to quickly retrue the outer (primary) tenon boss.


Another way you might like to try is to start with your blank mounted on a screw chuck from where you work the base and outside to the rough shape you want and form a tenon or recess for your chuck to grip the base.

Remove the bowl from the screw chuck, reverse it and mount on to your chuck jaws. You then remove the bulk of the material from the inside, to the wall thickness you deem appropriate, BUT you leave a pillar of wood in the centre with the screw chuck hole still in it.

Put aside to dry/warp/split/crack, hopefully not all of them, then when you remount just screw your screw chuck back in place and true the base mounting up again for a concentric grip. You can either true it up or make a new one if you've left sufficient thickness. Keep the revs low till you've got everything in balance, the pillar could snap if you have too much vibration going on.

This is less practicable if you are making small diameter bowls as you won't have much room to work between pillar and bowl wall but anything over 8" dia should be okay.


This is where the folks who use pipe flanges as faceplates have an advantage. They attach the pipe flange, rough turn the bowl, set it aside to dry (the screws help hold the bottom together), and it is ready to turn after tightening the screws.


Depending on the depth of the bowl, you can also put in your spur center, bring up the tailstock to original center mark and true the tenon for your four jaw chuck. I also use this method when starting smaller bowls. I rough them to round, cut my tenon and then mount in the chuck.


Another way is to leave a spigot on the inside as well as the outside.

When you resurrect the dried and distorted bowl, remount using the inside spigot so that you can then re-do the outside, and then reverse as you normally would to do the inside.

This works well and the spigot on the inside doesn't seem to afffect the drying.

In fact the additional mass tends to reduce the splitting in the foot area if a particular wood has a tendency to do this.


Aan easy solution which I like to use, especially in a production mode, is to hot glue on a scrap block. Either make a wooden faceplate to fix to your regular faceplate, or turn one to fit your chuck. Disk sand or plane the bowl bottom flat. Hot glue the faceplate to the center of the bowl. Mount and turn. Part off the face plate and finish the bottom. If you are power sanding to finish, you can mount the sanding pad in a drill press and use it to finish sand the bottom so it is concave.

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