Lantern Chuck

I first read about lantern chucks in Tubal Cain's book on workholding. There have been quite a few instances (such as my nut holder) where it would be useful to turn down screws. One option would be to use loose jaws like those described on Mike's Workshop. Another is a lantern chuck like this one.

The left-hand photo above shows the lantern chuck assembled and with an M6 cap-head screw held. The shaft shown at the bottom of the picture is 20 mm diameter and I hold this in an ER32 collet for machining. As can be seen from the right-hand picture, there are a number of components. The body (right-hand side) is 30 mm and the hole in the uppermost side is reamed to 12 mm. It is threaded internally to screw onto the drive piece (bottom of the picture). The hole in the side is 8 mm and is used with a tommy bar to tighten the chuck.

The piece in the top-middle of the right-hand photo is a 1/4" drive socket designed for driving 1/4" AF screwdriver bits like the hex-key bits in the top left of the picture. This is used to push the screw into the body and ensure that it turns with the chuck. The two washers underneath the bit are 15 mm outer diameter with a 12 mm reduced diameter to be a close fit in the reamed hole in the body. The holes in the washers are sized for different size screws.

These images show the drive piece. The left-hand photo shows the drive piece assembled with the screwdriver bit in place. The right hand photo shows the construction of this piece. The 1/4" hex driver on the right of the right-hand photo was made using my milling block with an ER32 collet block.