Whoa! Hold it down out there!

Keeping your workpiece from moving is gospel to CNCers and there are a million ways to do it. There seems to be no end of commercial hold-downs and clamps for CNC routing. Some are amazingly expensive. They may be clever and well engineered but to me they are all just consumables. I make my own out scrap stock and don't cry when I slice through one. I think it is a rare CNCer that hasn't hit more than a couple of clamps.


Before I show you my approach, what are the characteristics of good a hold-down?

  • First and foremost, it must be able to apply enough pressure to prevent the workpiece from moving.

  • Does not interfere with movement of the spindle or collet/nut.

  • Does not require contact to a lot of the workpiece to work well. This is to minimize waste.

  • Is sacrificial - if the bit hits it, the bit should survive.

  • Is very inexpensive and quick to make.

As you can see in the photo below, my clamps are simple. They consist of the clamp arm, a knob, a T-nut and 1/4-20 hex headed bolt. In some cases I also use a 1/4" washer. The clamp arm has a 1/8" x 1/8" rabbet in the end that allows me minimize the actual clamping area needed on the workpiece. Total cost for one clamp, using McMaster-Carr prices, is $0.20-0.35 depending on how long the 1/4-20 bolt is. Of course, you can find cheaper prices and may just have a few spare lying around in your shop. Since I used scrap wood for the knobs and arms, I price that at 0 because I would have otherwise tossed it out.


I designed my spoil board to incorporate T-Track that accepts 1/4-20 hex head bolts. The T-Track was purchased from Orange Aluminum and was surprisingly inexpensive. It didn't have screw holes but I didn't mind drilling them in order to save more than a hundred bucks. The clamps are easy to position along the track. I use different length bolts depending on the height of the workpiece. Below is an example of how I use them.





I make the clamp arms out of 1/2"/12mm plywood and the knobs out of 3/4"/18mm plywood. My clamp arms are 4" and 5" long. I have found 4" is just a little short with my T-Track spacing. Routing time for a batch of 6 with a 1/4" bit is around 4 minutes so it is pretty fast to make them. I tried making round knobs but found that the style I use allows me to turn them so they are away from the cutting area and do not interfere with the spindle. You can always add a quarter turn after it is tight. This allows me to clamp right up to the cut line even with a really short bit in my ER25 collet. In addition, the two arms give me more leverage when tightening.


Here are the dimensions of the wooden parts.

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