Bevel Bench — tools for people who make things

Find the cuts that won't work — before you cut them

Free stained glass pattern checker. Drop in your pattern and every piece comes back numbered, with the ones that are too small, too narrow, built around an inside curve you'll never grind out, or cut into a corner no score can turn, marked in red. Plus the glass you need per colour, and a printout at true size for the bench.

No sign-up, no install. Works in any browser, Mac and iPad included, and your pattern never leaves your own machine.

or drag an SVG pattern here — it never leaves your computer

Result

Pieces

#AreaNarrowestInside curveVerdict

Thresholds are rules of thumb from hand cutting and grinding. Change them to match how you work — a ring saw handles curves and corners a grinder head can't.

Stained glass pattern — numbered

What this checks

Four things go wrong between a pattern on paper and a panel on the bench, and all four are visible in the drawing long before you cut anything.

Pieces that are too small to hold

A piece under about a square centimetre is hard to grip against a grinder head without taking skin with it. The checker measures true area, not the bounding box, so a long thin triangle is judged on what it actually is.

Pieces that are too narrow to survive

Narrowness is measured as the largest circle that fits inside the piece — the honest measure of how thin the piece gets at its worst point. Below roughly 6 mm a piece tends to snap while you grind it, and it will not sit properly in came.

Inside curves that cannot be cut

An outside curve breaks away. An inside (concave) curve does not — it has to be nibbled and ground out, and below a certain radius the glass runs its own crack instead of yours. The checker finds the tightest inside curve on every piece and marks it on the drawing, so you can split the piece or open the curve while it is still just a line on a screen.

Inside corners that cannot be cut at all

This is the one that catches people out, because on paper it looks no harder than any other line. An inside corner is where the outline turns back on itself and takes a bite out of the piece — the notch in an L-shape, the slot in a border. A score has to run off the edge of the glass, and there is no path through that corner for it to take. A corner of ninety degrees or sharper is not a difficult cut; it is not a cut. Either the piece gets split in two along the corner, or it comes out on a ring saw.

The checker measures the angle of every inside corner and boxes it on the drawing — red where the break cannot be made by hand, amber where it is tight enough to cost you grinding. Smooth concave curves are deliberately left alone here: they are measured as curves, in the section above. Set the limit to match your own kit; drop it well below ninety if you have a saw.

Glass per colour

Every piece is measured and totalled by colour, with a waste allowance, so you can order glass without guessing. Fill colours in your pattern file become the colour groups.

Printing at true size

Print full size gives you the numbered pattern at the real dimensions of your panel, with a 100 mm ruler on the sheet. Measure the ruler after printing: if it reads 100 mm, your print scale is right and every piece on the sheet is exactly the size it will be cut.

Questions

What files can I use?

SVG, from Illustrator, Affinity Designer, Inkscape, Procreate exports, or anything that can save vector shapes. Each closed shape is read as one piece of glass.

Does my pattern get uploaded?

No. Everything is calculated in your browser. The file never leaves your computer, and there is no account to make.

Does it work on an iPad?

Yes. It is a web page, so it runs wherever a browser runs — including the machines the older Windows-only stained glass programs never reached.

Is it really free?

This tool is. Saving projects, exporting cut lists and working across several panels will eventually be a paid layer; the checker itself stays free.