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I have a circle cutter that I inherited from my father. The directions are long gone. It's bogging down and I'm sure sharpening it would help but it's kind of unclear which is the cutting edge. enter image description hereTruth be told, I'm not 100% sure which way the "blade" goes in. It is square and pitched from one corner to the opposite and I'm sure that the point need to be nearer the center (otherwise it wouldn't cut clean circles) but that still leaves two possible positions.

Q1. Does the point lead or follow the other side of the blade?

Q2. How do I sharpen it? I'm thinking put it in my vice and file an edge or two but which ones?

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The point leads. Otherwise, the tool will simply skate over the material.

As you indicate, it should be to the inside of the circle to produce a clean disk, or to the outside of the circle to produce a clean hole.

To sharpen, file or grind the entire end, keeping the face at same angle.

I hold mine at an upward angle against my fine grinding wheel with the point corner upwards.

Addendum: I know you didn't ask this, but while we're on the subject of circle cutters, I find that the imbalance of the spinning tool causes the drill to cut sideways with its flutes, enlarging the center hole and losing position. For this reason, I don't use a drill in the center of the cutter. I drill the pilot hole first and then use a smooth shaft of the same size.

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  • I also use a smooth shaft for modern hole saws from 5/8 diameter up to 4 inch. I drill the 1/4 inch pilot hole first, them use the holesaw with a smooth center shaft fitted. For metals, I use a few drops of cutting oil. It gives oily chips but a faster, more accurate hole. – John Canon Jan 27 '19 at 8:30
  • That helped. I don't have a grinder but ran the blade over a sharpening stone until the face was shiny and the edges sharp. I think I got more benefit from switching to a more powerful drill, though. – Chris Nelson Feb 3 '19 at 14:05

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