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Curiosity.diy · Laser bench

Kerf Hole Maker

A grid of test holes stepping around one target size. Push the actual dowel, bolt or bearing into each and find the one it grips — that hole size is the one to draw. Two rows, so it barely costs any board.

What this is for. A laser hole comes out wider than the line you drew, by roughly the beam width — the kerf. Draw a 6 mm hole and a 6 mm dowel rattles in it. This tool cuts your target size plus five smaller and four larger, round or as a 3–8 sided polygon so a hex pencil gets a hex hole. Try the real part in each: for a press fit (dowel, bearing housing) take the smallest hole it seats into by hand; for a clearance fit (bolt or pen you slide in and out) take the smallest hole it passes through cleanly. Draw that size on the real job and it fits first time. Roughly, kerf = part size − drawn hole that grips.

Sheet mode

One test block per sheet.

Target

Sheet

Document—
Holes10
Hole range—
Kerf window—

Download

Same page size, same origin. Engrave the JPG numbers, cut the SVG over the top without moving the board. The 4 mm square at top-left sits at 0,0 in both — line the squares up and the holes land on their labels.

Cut holes — SVG Engraved numbers — JPG Registration square at 0,0 — both files Your target size Pending block (combined mode) — press Add

How to use it

Cut the tester

  1. Engrave the JPG on the board you'll build from, at your usual settings.
  2. Cut the SVG over it without moving the board.
  3. Take the real part and try it in each hole.

Read it

  • Dowel / glue-up: the smallest hole the dowel pushes into snugly by hand. Glue swells timber, so leave it just shy of a hammer fit.
  • Bearing: the smallest hole the outer race seats into with firm thumb pressure or one light tap, no side-to-side wobble.
  • Bolt clearance: the smallest hole the bolt drops through freely. Go one step up if you want the head to self-centre.
  • Pencil / pen holder: for a stand you slide it in and out of, take the smallest hole it moves through easily; for a display grip, the one it holds. Measure a hex pencil across the flats with calipers and match the shape — a hex hole grips a hex pencil far better than a round one, but a round hole suits round barrels.

Why the drawn size isn't the part size

The beam eats a little material all the way round the circle, so the finished hole is larger than the line — usually by 0.1–0.25 mm on the diameter depending on machine, power, speed and board. Read the engraved number under the hole that fit, draw that on the real job, and note it on the wall beside your comb figure. Recut this whenever the board or settings change.