Simple CNC Clamp Workholding System

So I wanted in the CNC game, played with the idea of building one but opted against it and went out and bought myself a Probotix Fireball X90.  It's a pretty slick machine, easy to assemble, but not entirely complete in my opinion. One of the major shortfalls to me is the lack of any type of work holding system. Yes, I could have plopped down $259 for an aluminum T-slot board, but daaaang I'm cheap.  Yes, I can do like I've seen others do before and just screw my work in place, but I've done that and was not very happy with the process. Beyond needlessly butchering my spoil board, it took forever.

I've worked on a wooden CNC machine before and it used a basic screw-down system, but I found so many times that I spent as much time hunting down screws and washers and clamping down my work as I did milling simple parts.  I also found screw-down systems caused me to use larger material than needed to accommodate the fasteners and to get clearance for the router. I needed something different.

After long thought I came up with a simple solution.  My favorite tool shop sells these great little aluminum bar clamps for about $10.  I would need two.

I would devise a way to attach these bar clamps to my CNC bed horizontally and these would hold my work.  I would now be able to fasten my material to the table quickly, easily and without getting in the way of the router.  I started by making two sets of plywood braces that would hold the bar clamps as close to the outside edges of the bed as possible.  The rectangular holes in each must provide for a snug hold but still allow for easy movement.  The braces are held to the Fireball's frame with three bolt-and-washer connections.

The vise-action side of the clamp would protrude in the front of the machine attached to the wooden brace in front by two small bolts run through two small holes easily drilled in the aluminum bar clamp base.

To gain a small bit of clearance I ground off the lip on the moveable boot for the clamp. About twenty seconds on the grinder and this step was complete.

Here you can see the bar clamp installed in the braces.  The clamp is simply threaded through the rear brace, not screwed or glued in any way. The only thing permanently affixing the clamp to the brace is the two small bolts mentioned previously. The clamp must be able to slide back and forth through the wooden braces.

With the addition of two wooden braces (painted spiffy black) the clamps can be tightened in seconds holding my material quite firmly for routing.

 

There was about eight or nine inches of excess bar clamp that hung out of the backs of the braces, I just cut that off and used the little butt-end plastic piece in the now custom length bar clamp.  I was worried at first that the addition of the clamps would reduce the working area of the CNC table but in actuality it doesn't since the router bit can't actually get but a few inches from the side of the table anyway. All in all, I'm quite happy with this. 

Enjoy.