Milling know-how
Setting holding tabs correctly: so the part does not fly on the last cut
The most critical moment of a milling job is the last millimetre of the outer contour: as soon as the cutter separates the part from the rest of the sheet, it is loose. Without support it jams against the spinning tool, picks up chatter marks or, in the worst case, flies across the workshop.
Holding tabs solve the problem: at a few spots along the contour, a small bridge of material remains that keeps the part connected to the sheet until the end. After milling, the tabs are cut by hand and sanded flush.
Set holding tabs directly: to the CNC milling tool →
How to do it in step2gcode
- Upload your file and configure the contour operation as usual.
- Enable holding tabs in the settings, selectable separately for outer and inner contours.
- Pick a material preset: tab width, height and angle are pre-filled with sensible values and can be adjusted if needed.
- Check the 3D preview: at each tab the toolpath lifts briefly, so you can see where the tabs sit.
- After milling, cut the tabs with a chisel or utility knife and sand the stubs flush.
Which tab size for which material?
As a rule of thumb: soft materials take tabs 12 to 15 mm wide and 3 to 4 mm high; brittle plastics and metals 8 to 10 mm wide and 2 to 2.5 mm high. step2gcode pre-fills the tab dimensions based on the material preset. The logic behind it: soft materials tolerate wide tabs because they are easy to cut through. For brittle or tough materials, smaller tabs are better, otherwise removal becomes a chore or the part breaks out during separation.
| Material | Tab width | Tab height |
|---|---|---|
| Wood (softwood/MDF) | 12 mm | 3 mm |
| Hardwood | 15 mm | 4 mm |
| Acrylic/plastic | 8 mm | 2 mm |
| Aluminum | 10 mm | 2.5 mm |
When you can skip the tabs
If you work with double-sided tape, a vacuum table or a spoilboard with the stock screwed down, tabs can often be omitted, since the part is held across its whole surface. For aluminum the rule still stands: never cut through without secure fixturing. A loose aluminum part on a spinning cutter is no longer scrap, it is a projectile.