A Cheap and Easy to Make Lathe Chuck Spider (Spacer)

A small project that is long overdue for my 7x14 lathe. A Chuck Spider. How often have I battled to turn down a short part that needs a spacer behind so it protrudes beyond the chuck jaws.

A 100 x 150 mm plastic packing shim 10mm thick (or other thickness). Available from hardware store. Our local prices are between $2 and $4 depending on the size and thickness of the shim. Look for shims that are flat - some can be slightly warped. (I've shown a yellow shim in this example purely for the photo. The 100 x 150 x 10 is black)

I see these made in aluminium and I'm sure that's the best material to use. I found the local Bunnings hardware store keeps plastic shims for packing joists etc., so I decided to try them.. They come in a variety of sizes and thicknesses. As I have a 100mm chuck I chose the 100 x 150mm shims and for this one - 10mm in thickness. They can be slightly warped so I looked for ones that are pretty flat. They turn very easily. I faced off both sides of the shim with a final thickness of about 8mm.

It is often necessary to turn down a short part that that doesn't protrude enough from the chuck jaws. It's normal to hold a part in a chuck with the back firmly butted up against the face of the chuck. You can just move the part forward to clamp closer to the jaw ends, but you could then clamp the part off true, particularly when you have a part that has a true and faced off back.. It's far better to have a spacer behind the part which also butts up against the chuck surface. I have sometimes tried placing a large hex nut behind the part but it's always a fiddle to set everything up.

A properly made Spider sits flat against the chuck face and also extends up the sides of the jaws allowing for larger parts to be fitted into the jaws easily.

The spider needs to be made to suit the length of part being turned (thickness of the spider) and the diameter of the chuck. Different Spiders can be made up in various thicknesses to suit the individual need.

I cut the shim down to 100 x 100 using my table saw (cuts easily). Mark out a circle for the chuck diameter and cut the circle using a band saw of coping saw etc.

Now, using the alternate jaws in the 3-jaw chuck, face off both sides in the lathe. My final thickness came to around 8mm.

I made a drawing in SketchUp drawing the one leg with a gap of 15mm to slip over the jaw. Then I did a circular copy of 120 degrees repeated twice. That gives a perfect fit to all three jaws. The printed size wasn't an exact fit so I did some maths to adjust to the correct size on the copier, and it came out perfectly.

I cut this out and using the kids school stick glue fastened the drawing to the shim and hand cut down the lines using a tenon saw and coping saw. I then hand filed the extra recesses in the jaw gaps, and the cleaned up the edges with the file and some fine water paper.

Use a flat file and fine water paper to clean up the surfaces and edges. Plastic tends to leave a fluffy burr on the edges which need to be taken off. The paper and glue comes of instantly in warm water.

Here's the Spider fitted - and a final picture of why a Spider is very useful.

I'll be making some more of these with various thicknesses (and also for the 4-jaw chuck)

If you own a 3D printer this is a project for you too.