What fails when the kerf in the plan does not match the blade

When the kerf in the plan is thinner than the blade on the saw, the layout still fits on screen. But every cut takes more material than the plan left for it, and the shortfall lands on the parts you cut. The saw kerf you enter has to come from the blade mounted on the saw for this job.

One kerf setting becomes the gap between every part

Kerf is the gap the layout leaves for the blade. In CutGrid it is one setting for the whole project. The layout places that gap beside every part, on every cut line. A sheet with five parts across has a kerf gap between each pair, and the same again down each column. The value is the full width of the slot the blade cuts, not half of it.

That is why one wrong number does not stay small. An error of half a millimetre is half a millimetre on a single cut. But it repeats at every gap along a row, and again on every row down the sheet. On a long row, that adds up to several millimetres by the last part. The plan applies the value exactly, so whatever you typed is what every line in the layout assumes.

Trim is a separate margin taken off the stock edge before parts are placed, so it does not cover for a kerf set too thin. Linear jobs work the same way. On bars, pipes, and profiles, the kerf sits between each cut length. The leftover length shown on the bar already has those gaps taken out.

A list that fits without the blade can need an extra sheet

Picture a row of parts laid along the width of a sheet. At zero kerf, the parts sit edge to edge and the last one ends just inside the usable width. Count the blade, and each gap pushes the next part a little further along until the last one no longer fits in the row. The layout moves it elsewhere on the sheet. If no space is left there, it goes onto a new sheet.

Before trusting a row that looks tight, add it up by hand. Take the part widths, add one kerf for each gap between parts, and add the trim taken off the edges. If that total comes within a blade's width of the sheet width, a kerf that is off by a little decides whether the row fits.

The kerf and trim guide shows a worked pair of layouts for the same parts, one without the blade and one with it. Its sheet counts are recomputed from the optimizer, so read them there. On your own job, run the list once at zero kerf and once at the real value. If the sheet count changes, the plan was tight before the blade was counted.

A kerf set too small fails at the saw, not on screen

Which failure you get depends on how you cut. If you saw to the marked line, each part loses the extra blade width and comes out short. If you hold every part to size, the extra comes out of the sheet, and the shortfall waits at the end of the row. Either way, check the first row before cutting the rest. Measure the parts against the plan and the material left for the last one.

A kerf set too wide errs the other way. The plan leaves a little more gap than the blade needs, so each part has a sliver of spare material beside it. That costs some offcut, and on a tight list it can cost a sheet. But the parts you cut still come out at full size. If you are unsure between two values, the wider one is the cheaper mistake.

Measure the saw kerf from the blade that is mounted today

A kerf value typed for the last job says nothing about the blade on the saw today. A thin-kerf rip blade, a crosscut blade, and a blade that has been resharpened can each cut a different slot. The figure printed on the blade is nominal, and the tooth set can differ from it. The check takes a few minutes and uses one strip of scrap. If two saws share the shop, measure each one.

• Cut a slot into scrap from the same stock, at the feed rate you will use for the job.
• Measure the slot width with calipers in two or three places and take the widest reading.
• Write the reading and the blade name on the scrap, or on a label kept by the saw.
• Enter that value as the project kerf before running the layout.

Keep the marked scrap near the saw. Next time the same blade goes on, you have a measured saw kerf to compare against instead of a guess. If the blade has been sharpened or swapped, cut a new slot. On linear jobs, do the same on the chop saw or band saw. That blade has its own kerf, and the bar plan depends on it.

In CutGrid the kerf sits with the project, so a saved project carries the value it was planned with. Before reusing one for a new cut, compare that kerf against the slot you measured today. If they differ, change the setting and run the layout again before any sheet goes on the saw. The new layout may place parts differently, so mark and cut from that one.