Securing the Work Piece on the ShopBot
On the laser cutter we merely set our piece inside the cutter and don’t need to hold it down. The CNC router is a much larger and powerful machine and will knock the workpiece all over the place causing damage and potential injury. We need to firmly secure our material to the router table before using the machine. It is important to make sure that any fasteners used to secure the workpiece do not come in contact with the spinning router bit.
The simplest way to secure the workpiece is with screws attached directly to the cutting surface. It is important to pre-drill holes through the material to avoid splitting the plywood. The pre drilled, or pilot hole, should be large enough that the screw spins freely in the hole but the head of the screw does not fit through. Screws function as clamps. If the screw cannot spin freely in the top piece of material, then it will not create a fully clamping force.
For pieces that would be marred by screw holes, a hold down clamp can be used. This is an L shaped piece of wood that has a rabbet, or L-slot, cut out of it that is shorter than the height of the material being held down. Then screws securely clamp the hold down to the cutting surface, thereby holding down the material.