Resource
Hold-down map
Clamp placement map for first CNC cuts.
Who uses a hold-down map and when it matters
Machinists and bench teams at FET colleges, mall sign shops and plant buyers setting up their own in-house CNCs all use a hold-down map. It's a basic but essential reference when you’re starting out, laying out your first workpiece, or swapping new panel shapes on a busy Germiston bench. A hold-down map helps your operator avoid work moving mid-cut, a serious issue when plywood bows on a hot Highveld afternoon, or when humid KZN air warps a signboard. For first-year teams, even a basic MDF job can go wrong fast without a mapped clamp set. Shopfloor supervisors use these maps to train newer hands and double-check clamp coverage before firing up a job.
How a hold-down map works in your shop
You start with a top-down sheet outline, then mark key clamp points around edges and sometimes inside large cut-outs. The map usually shows common clamp types: step clamps or hold-down bolts, spaced for your bed size. On a typical 1250 x 2500 mm aluminium table, you'd see 8 to 12 clamps marked, with focus points at corners and along long edges. The central area often gets one or two shadow clamps, but don't crowd the toolpath. Record the material type on the map, since thinner foams or plastics need closer clamp spacing than thick birch or composite. If your team’s switching between 9 mm and 18 mm MDF, it’s best to keep two different map sheets taped up next to the machine.
- Panel outline and thickness called out
- Clamp types labelled for each spot
- Clear keep-out zones for spindle and toolpath
- Bed size and material written on each map
Worked example: prepping a hold-down for a new job
Let's say you’re setting up a 610 x 1220 mm shutterply sheet for a mall kiosk fitout at Boardwalk. The supervisor pulls out the 610 x 1220 hold-down map. They mark 6 clamp spots: two at each short end, one each side. They adjust two clamps a bit inwards to make room for a zigzag toolpath near the edge. Minimum 70 mm clearance between spindle launch and the nearest clamp. Shadow clamps are placed at 200 mm from either end as a backup. The loader notes the day (Wednesday, after a power-cut delay), clamps down, and waits for a sign-off. It’s easy to miss a step if your team’s on its second big job of the day, so someone always double-checks clearances before spindle up.
Common mistakes South African shops make with hold-down maps
Alot of new teams forget to update their hold-down map when swapping to a different sheet size, leading to under-clamping and ruined panels. Sometimes, people assume more clamps equal better grip, but over-clamping can warp thin plastic on humid coastal days. It’s also common for teams to skip writing the clamp type or material on the map, which causes confusion when switching crews. Missing the keep-out zone for your toolpath is another standard error that risks hitting a clamp at 12000 rpm.
Tell us about your bench
Share the bench you run and the week you are packing for. Sunnyrock replies with a considered shortlist, not a megacatalogue.