Panels, timber and cutting plans

KerfCraft knows two main kinds of part that you cut: panels and timber members. This page explains how each kind is sized, why the grain direction matters, and how the cutting plan uses the saw kerf.

Panels and timber members#

A panel is cut from a sheet material, for example 18 mm plywood or MDF. The sheet sets the thickness of the panel. A timber member is cut from a length of timber with a known section, for example a 47 × 100 mm stud. The section sets its width and thickness.

The cut list gives each part as length × width × thickness. The length is always along the grain. For a panel, the grain direction is a property of the part. For a timber member, the grain is always along its length.

Why the grain direction matters#

Many sheets have a grain or a pattern, for example a veneer. A tall side panel usually has its grain along its height. If the grain matters, the cutting plan keeps the length of the part along the length of the sheet. If the grain does not matter, for example on MDF, the cutting plan can turn the part 90°. This often uses fewer sheets.

To set this for a panel, use Grain matters in Properties. If you clear it, the optimiser can turn the part on the sheet.

Kerf and margins#

The kerf is the width of material that the saw blade removes in each cut. Two parts next to each other on a sheet need the kerf between them. If the kerf in KerfCraft is too small for your saw, the parts come out too small or do not fit.

The sheet optimiser also trims 10 mm from each edge of a sheet, because the factory edges are rarely clean. For timber, the optimiser removes an end trim from each length before it plans the cuts.

To change the kerf and the end trim, select nothing. Then use Saw kerf and End trim under Workshop in Properties. The default kerf is 3 mm, and the default end trim is 5 mm.

How the optimiser plans a sheet#

The sheet optimiser makes guillotine cuts only. Each cut goes from one edge of a piece to the opposite edge, as on a panel saw or a track saw. It tries many orders and cut rules, and keeps the plan that buys the fewest sheets. If two plans buy the same number, it keeps the plan with less waste.

The optimiser also calculates the minimum number of sheets that the area of the parts needs. If its plan uses that number, the plan is the minimum. If not, a better plan can exist, but the optimiser did not find it.

Try it#

The planner below runs the same sheet optimiser as the app, with the same margin. Change the sizes, the kerf or the grain, and look at the sheets. The planner shows only the sheet layout. In the app, the Cutting plan tab also shows the cut order and the timber lengths.

A cutting plan helps you buy and cut. It is not a guarantee. Check every dimension against your own measurements before cutting. Read What KerfCraft checks and what you must check.