On Thingiverse there are HUNDREDs of items that can be fabricated on a 3D printer, and a few items that can be made on our Zen CNCs. One such item is the CNC Table Clamps project: http://www.thingiverse.com/thing:776
Of course the project only provides a DXF file. I'm a bit of a newbie to working with those files, so no doubt there are better ways to do this. I took the DXF file into HEEKSCAD, eliminated the largest size of the three, scaled the rest down so the clamps would be around 4 inches long, rotated it 90degrees, and double checked that the hole is indeed 5/16" so I could use a wooden dowel to fasten the halves.
I brought THAT DXF file into CAMBAM 0.82 (and let me say that version is rough around the edges but I simply can't afford to spend more on software), and set it up to do the round holes as a machining profile, then a pocketing profile, and then machining profile to cut the clamp itself out. If I had the moolah, I would splurge and get Cut3D by Vectric.com which makes it really easy to add cut-out tabs to hold your part in place; BUT I just cut the whole thing out and the sawdust held the part in place mostly.
OK, from CAMBAM, I created the tooling profiles. I used the 1/8" endmill sold by ZTW for the whole job. For material I used 1/2" plywood (I could have easily used 1/4", just know this G-Code is for 1/2") on my ZTW 12x7x5.
I use EMC2 to control my CNC so I opened the G-code in it and went from there. I pretty much ran 12 inches per minute for the whole thing and it did just fine. It took about thirty minutes to run the whole thing.
EMC2_screenshot by jackspace, on Flickr
Here's the G-Code:
What you get are four pieces: two for a big clamp and two for a small one. Give them a light sanding and glue them together and insert your bolt and knob/nut/wingnut and you have a pair of handy CNC Table Clamps, which you can replace when you run your router over one by accident by just cutting some new ones out:
CNC Table Clamps by jackspace, on Flickr