How to cut glass: score, snap and plan the order of the cuts

This guide is about planning the cuts: the order, the allowances and what is left over. How to hold the cutter and run the score is learned at the table, from the cutter’s maker and from somebody who does it every day; this page does not teach it.

1. Score and snap: every cut runs edge to edge

A line is scored on the surface and the glass is snapped along it. The snap does not stop where you would like it to: it runs to the far edge of the piece. A layout with a small piece tucked into a corner, which is fine on a panel saw, cannot be cut on a glass table. That is why a free panel nester promises more pieces per sheet than a glass table can deliver, and why the glass cutting optimiser only lays out guillotine cuts.

2. Take the edge trim off first

The edges of a delivered sheet are not used: the usual edge trim is 10 mm per side, 10 to 15 mm on a delivered sheet. An offcut from your own rack takes none, because it was cut in your shop and its edges are already clean. On a DLF sheet of 3210 × 2250 mm, 10 mm a side leaves 3190 × 2230 mm of usable glass. Between two pieces you also lose the breakout, typically 3 to 5 mm; the optimiser starts at 4 mm. The figures are on the glass reference.

3. Strips, then columns, then panes

A glass layout is cut in three stages. A strip is snapped off the full width of the sheet, as tall as the tallest piece in it. The strip is cut into columns. Each column is cut across into the panes stacked in it. A new strip starts when the next piece will not fit, and each strip is finished before the next one is cut.

Here is the first sheet of the optimiser’s «windows» example, 4 × 1000 × 1200, 6 × 600 × 1200, 4 × 800 × 500 mm, as the optimiser lays it out. The numbers on the drawing are the order of the cuts, and the list under it is the sequence the cutting plan prints for the table, measured from the top left corner.

1. Trim 10 mm off all four edges — leaves 3190 × 2230 of usable glass
2. Strip 1 — cut across at Y = 1210 mm — frees a band 3190 × 1200 mm (from Y = 10). Work on this strip before cutting the next one.
3. Rip at X = 1010 mm — column 1 of strip 1, 1000 mm wide (allow 4 mm breakout)
4. Last piece of the column → A1 — 1000 × 1200 mm
5. Rip at X = 2014 mm — column 2 of strip 1, 1000 mm wide (allow 4 mm breakout)
6. Last piece of the column → A2 — 1000 × 1200 mm
7. Rip at X = 3018 mm — column 3 of strip 1, 1000 mm wide (allow 4 mm breakout)
8. Last piece of the column → A3 — 1000 × 1200 mm
9. Strip 2 — cut across at Y = 2214 mm — frees a band 3190 × 1000 mm (from Y = 1214). Work on this strip before cutting the next one.
10. Rip at X = 1210 mm — column 1 of strip 2, 1200 mm wide (allow 4 mm breakout)
11. Last piece of the column → A4 — 1200 × 1000 mm (rotated)
12. Rip at X = 2414 mm — column 2 of strip 2, 1200 mm wide (allow 4 mm breakout)
13. Cut across at Y = 1814 mm → B1 — 1200 × 600 mm (rotated)
14. Rip at X = 2918 mm — column 3 of strip 2, 500 mm wide (allow 4 mm breakout)
15. Cut across at Y = 2014 mm → C1 — 500 × 800 mm (rotated)

Solid line: the strip cut, across the whole sheet. Long dashes: a column. Short dashes: a pane cut out of its column. Dashed outline: an offcut.

4. The order of the list decides the sheets

Which piece goes first changes the layout. The optimiser runs every list through six orderings and keeps the best. For this order of 14 panes, the orderings need between 2 and 3 sheets:

By hand you try one; on some lists the difference is a whole sheet.

5. Keep the offcuts

Three kinds of rectangle survive this way of cutting: the band above the last strip, the end of a strip past its last column, and the space above the last piece of a column. Anything at least 150 mm on both sides is worth racking; below that it is a sliver. The offcut inventory keeps them, and the optimiser cuts the next order from the rack first, but only when that saves a new sheet.

6. Print the plan and label every pane

The cutting plan prints each sheet with its pieces, the cut sequence with the measurement of every cut and the offcuts to rack, and the cutting labels give every pane its code, size and reference in cutting order. Three worked orders show the whole thing with figures.

Handling

A freshly cut edge is sharp: work with gloves and safety glasses. And weigh the sheet before you lift it: a DLF sheet of 6 mm weighs 108.3 kg, past what two people should lift. The glass weight calculator gives any pane and how many people it takes.

Questions people ask

Why does glass have to be cut edge to edge?

Because glass is scored and snapped, not sawn, and the snap runs the full length of the piece being held. A cut cannot stop halfway, so every cut divides a piece from one edge to the other: a guillotine cut.

In what order do you cut a sheet of glass?

Take the edge trim off, snap a strip off the full width of the sheet, cut the strip into columns, then cut each column across into panes. Finish each strip before cutting the next one.

How much edge trim is taken off a glass sheet?

Usually 10 mm per side, 10 to 15 mm on a delivered sheet, and none on an offcut from your own rack. On a DLF sheet of 3210 × 2250 mm, 10 mm a side leaves 3190 × 2230 mm of usable glass.