What should I enter for Clearance and Border Gap when nesting plywood, and how do I keep the grain running the same way on every part?

How the spacing is calculated

In Nest Parts the minimum gap between two parts is Tool Dia. (D) plus Clearance (C). The official example: a 0.25 inch tool with 0.05 inch clearance gives 0.3 inch between parts. Border Gap is added to the Clearance around the edge of the nesting area, so it sets how far parts stay from the sheet edge.

Numbers production suppliers publish

A tooling supplier's nesting guide recommends:

• Part spacing of roughly twice the tool diameter (about 0.50 inch for a 1/4 inch bit) so chips clear and heat stays down. With a 0.25 inch tool that means a Clearance of about 0.25 inch.
• Border Gap of 0.25 to 0.5 inch on good sheet stock, and 0.75 inch or more on lower grade or warped plywood, to stay clear of damaged factory edges.
• A hold-down buffer of 0.5 to 1 inch for vacuum tables and 2 inches or more where clamps sit.

The minimum the software allows (tool diameter plus a small clearance) packs more parts per sheet, but leaves a thin web between parts. Shops that cut small parts on vacuum report leaving 0.5 to 0.75 inch of material between small parts so a solid frame remains to hold them.

Controlling grain direction

1. Rotate Parts to find best fit decides whether parts may turn. Uncheck it and every part keeps the orientation you drew it in, which is the strict grain lock.
2. If it is checked, the Rotation step angle sets the increments the software may use. A 180 degree step keeps the grain on the same axis while still allowing some flipping end for end.
3. Mirror parts to find best fit flips parts over. The documentation says to check it only when the direction the parts are cut in is not important, so leave it off for sheet goods with one good face.
4. The same supplier guide lists hardwood plywood, veneered panels, solid hardwood and decorative laminates as materials that need restricted rotation, and MDF, HDPE, acrylic and PVC as free to rotate.

Pro tips

• Draw grain-sensitive parts in the correct orientation before nesting. With rotation off, the nest can only keep what you gave it.
• To nest into an offcut or avoid a damaged area, put boundary vectors on their own layer and choose it under Nest boundary. Several vectors can be used, so holes and excluded zones are respected.
• Measure the sheet before you nest. The supplier guide notes that being off by 0.02 inch is enough to cause trouble in production.