Center in a Four-Jaw Chuck
by Using a Silhouette
by Don Peterson

A couple of decades ago my two dial test indicators had failed and I needed to center some round stock in a four-jaw chuck. I found this method works nicely.

First, put a cutoff tool in the tool holder and a piece of white paper on the lathe's apron. Then, shine a light on the paper to illuminate the gap between the work and cutting tool in silhouette. Bring the tool close to the work and you can see the gap width vary when you turn the chuck by hand. Adjust out the variability in the usual way.

I found that with care I could center work so that a .0001” dial indicator wouldn't move – though most of the time the work isn't round enough to do this. I've never bothered getting those test indicators fixed, as I use this silhouette method whenever I need to center something. It's obvious once you see it, but I've never read of anyone doing this. Instead of paper, I use a chunk of white plastic that hangs up on a rod at the back of my lathe.

One side of the plastic is textured and I prefer to use it over the other side, which is specularly reflective. Give it a try – you may prefer this method to using an indicator.

Note: Regarding our LAST TIP, be sure when using a Tool Lanyard that you secure it to a magnet attached to the machine and not yourself. The technique is meant to be used only when the machinery is off. Spinning spindles and lanyards do not mix well!

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