After moving the ShopBot and rebuilding it, we came to a crossroads for our holddown solution. Up until now we’ve used Raptor polymer nails to secure materials to the spoilboard. This works better/safer than using drywall screws on material you can drive a nail through.
The pro solution would be installing a 3 phase pump and building a vacuum table. We don’t do production work or need to optimize our workflow so that price tag is hard to justify. Our “make it a little better” solution is installing t-tracks, rails of extruded aluminum for attaching fixtures and clamps.
There are many sources for tracks. We have been collecting items made by Woodpeckers who have an engineering eye for precision when using handheld tools. They offer a heavy duty track called the “Super Track” that is compatible with standard 1/4in-20 bolts. (Some track vendors makes systems that aren’t interchangeable.) Super Track has a channel on each side, two on the bottom, and three on the face so it can be configured in any direction and comes in lengths of 6, 12, 24, 36, 48 and 60 inch.
To figure out how to setup our track system, we had to look at what we do the most. As incredibly flexible as a complete grid of Super Track on 24in centers would be it felt like over-engineering before we’ve ever used t-track.
The next projects on our list all deal with plywood. The easiest way to secure plywood with tracks is to run sections the length of the plywood’s edges and use clamps. The dimensions of the ShopBot’s frame gives us 5ft by 10ft so pieces of 60in Super Track fit either orientation. The multiple channels in Super Track will let us attach fixtures to square the materials where a single channel allows an attachment to rotate.
The easy path is installing two pieces of track down each side of the spoilboard. Bolts provide more strength for holding the track where screws can pull out. Bolts can easily be removed if we change our design later. We’re stainless steel 1/4in-20 bolts with flat washers, split washers, and nuts.
After determining the center of the channels on the track’s bottom, we mark locations to drill 1/4in holes through the work table surface. We’re using 6 bolts per track section and see if that provides enough support.
Here are two sections running the length of the X-Axis.
The track sections run beyond the length of the spoilboard and to the edge of the work table surface.
To hold down a sheet of plywood the simple heavier duty clamp should work.
A Knuckle Clamp provides gripping from various angles due to the non-slip hinges and range of pivot points.