By Don Wiederhold
While this trick has been around for about as long as there have been lathes, some of the readers may be unaware of it. Or perhaps they have heard of this method for setting tool height on a lathe but are unsure as to what is meant by, “Just use a scale to set it.”
In Photo 1, I have exaggerated the angle for illustration purposes, but when the top side of the scale is leaning away from you, it indicates you have the tool set above the centerline. The setup in Photo 2, with the top of the scale leaning towards you, indicates you have the tool too far below centerline.
The ideal position is when the scale is absolutely vertical (Photo 3). If you are going to be off a bit, it’ll be better to be slightly below the center. You will know real quick whether the tool height is correct when you make a face cut. If you leave a little stub, you are too low. If you feel more tool pressure than normal, you are too high. (This is assuming you have a correctly sharpened tool.)
This is a very quick method and is really handy if you are changing a lot of tools. Just make sure to pinch the scale lightly (especially with brazed carbide) so you don’t harm the cutting edge.