Tools - Stubby Key for Chuck

• Adjusting a four jaw chuck can be made easier by the use of a second chuck key (chuck wrench), or alternatively by two purpose built short keys. The shorter chuck is easier to manipulate in the small space available, and by using two keys - one to tighten and one to loosen opposing jaws, the job goes a bit faster. Be sure to use the full size chuck key for final tightening.The build I describe here is probably a bit more complex than it really needs to be, but it gave me an opportunity to try some different machining techniques, and made use of the materials I had available. Here is a description of the build procedure:Mill the end of a square (stainless steel) rod down to a size to fit the chuck
• Turn about 1" of the rod (behind the key end) to a cylinder, and thread it with a die
• Knurl a short piece of 0.75" aluminum rod; drill and tap it to fit the key section
• Screw the two pieces together

Now, this could have been made from a single piece of stock, but I didn't have anything handy at the time except aluminum, and I didn't want to make it from pure aluminum as I thought it would be too soft on the key end. Also, using square rod made it very simple to mill the square key, as I could simply mill one side, rotate it in the mill vise, mill the next side, and so on.

I should add here that before I got my mill, I successfully made a full size chuck key by carefully squaring the end of a steel rod on a bench grinder. With that in mind, this entire project could be made with only a lathe and a bench grinder (or even a file, with a little patience).

This build is so simple that it doesn't really need plans, but I went ahead a drew some up anyway. Keep in mind that the key size for your four jaw chuck may well be different from mine, so adapt these plans to fit your chuck. You may also want to make the key stem a little bit longer than I did - if I had it to do over I would probably make the stem 1/2" - 3/4" longer.

• Plans in PDF format : https://docs.google.com/file/d/0Bykt5WZ092aWeWZVZWhKaUVaVms/edit
• Plans in LibreOffice Draw format : https://docs.google.com/file/d/0Bykt5WZ092aWVUlBbVlEbnJpYlE/edit

Note: This build was inspired by a similar project by David Morrow. You can find a link to his build (and others) on the Useful Links page of this website (look for "stubby chuck key" in the Lathe Tools section).

The Build

Start by milling the end of a square stainless steel rod down to a size to fit your chuck. The raw stock doesn't have to be square (though that certainly makes the milling easier), and it doesn't have to be stainless steel. I didn't use aluminum because I didn't think such a soft metal would wear well, but I have seen full size chuck keys made of aluminum, so it might well work.

Chuck the square rod in your lathe and turn a section down to a cylinder.

Cut the piece to length by parting on the lathe, and then partially thread a section of the cylinder (see other picture below).

In the lathe, knurl a short section of aluminum rod, and drill a hole to be tapped to fit the piece above. Chamfer the piece after knurling - chamfer both "ends" by doing a partial parting cut and then chamfering the exposed "end."

In the photo to the left, the rod has been turned smooth, but not yet knurled or drilled.

Here is the finished piece after knurling, drilling, chamfering, parting off a 1/2" section, and tapping.

Here are the two pieces ready to be screwed together. Note that the key section is not fully threaded - it should be threaded just enough so that when the knurled piece is screwed on, the ends of the two pieces are flush.

Before screwing the two pieces together, degrease, apply permanent thread lock and then screw the two pieces tightly together.

Allow the thread lock to set, then chuck the assembled unit in the lathe and face the end to make it perfectly smooth. This is just for cosmetic reasons, so you can skip the final facing if you like.

Here again, the completed stubby keys. I made two so that I could use them on opposing chuck jaws.

Reminder: These are for adjustment only. Be sure to use the full size chuck key for final tightening.

Here is the chuck key in the chuck (chuck removed from lathe for photographing).

Note that there is some limitation on the allowed outward travel of the chuck jaw - make the stem part of the stubby key longer if this is a problem for you.

This photo shows how the stubby keys are used on opposing jaws to make adjustments (chuck removed from lathe for clarity).