# Clamping a workpiece to my CNC table



## roli_bark (Jul 17, 2010)

Hi,
I'm planning to attach a sacrificial Plywood board onto my CNC table.
During the process, I'm planning a metal rail-guide (about 5" long) attachment for a De-Sta-Co 225-U clamp (Horizontal Hold-Down Toggle Clamps). The goal is to fine adjust the location of the clamp to the workpiece size, while it is still loose (before clamping).

I'm looking for 8 x metal rail-guide parts similar to the metal rail depicted below.

The rail is going to be assembled in a groove milled at the sacrificial board bottom side, such that the attachment screw head is flush to its surface. 

The Clamp is going to be attached to the sacrificial board top side.

Each of the 4 clamps is attached with 4 screws, 2 per rail, and moveable (while still loose) along 2 rails.

Where can I get this metal-rail guide part similar to the picture ?
Thank you in advance !
Roli


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## Dr.Zook (Sep 10, 2004)

Welcome to the RouterForums Roli. Glad to have you join in.


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## roli_bark (Jul 17, 2010)

I may have found a simple solution in the part below 
(a Chest Drop Door Lid Stay Support), that can be "hacked" to my purposes.

The only problem with this is the lack of these 90 degrees edge bends,
which allow bottom (hidden) HEX screw head fixation when tightening the Clamp.


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## Metalhead781 (Jul 27, 2010)

Have you considered a simple keyhole bit and using your machine to make hold downs? With my machine, my spoilboard gets so chewed up i'm milling off 1/16" every three to four days. For this reason I simply use screws, oak holddowns and blocks to keep my material in place. If you're not going to use your machine as much as i do, using the machine itself with a keyhole router bit making inverted t slots in the spoilboard would probably be the simplest way. Then all you have to do is mill some cam type hold downs with a thru hole. Use a bolt to match the keyhole slot and a knob on top. If your material thickness varies much like mine does, elongate the thru holes. My 2" long oak holddowns can clamp anywhere from 1/8" to 1" material. For anything thicker i use a scrap piece and 1/2" thick maple blocks 1" wide. The screw or in this case, the bolt, goes between the material and the scrap block for the clamping action. 

Best of Luck
Randy


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## roli_bark (Jul 17, 2010)

Thank you Randy for your good tips. 

Some I will adpot. But rather milling keyhole,
I think I'll go with Rockler [3/8" deep] Aluminum T-Tracks mounted on top of the sacrificial board. When it is chewed up, dismount the T-Tracks off it, and re-mount them on a new sacrificial board.

I assume that the the sacrificial board strength [@thickness of 3/4"] will suffice the 3/8" deep grooving for the T-Track thickness.

The clamps will be moving along the T-Tracks on top of small solid wood rectangle pieces.


Metalhead781 said:


> Have you considered a simple keyhole bit and using your machine to make hold downs? With my machine, my spoilboard gets so chewed up i'm milling off 1/16" every three to four days. For this reason I simply use screws, oak holddowns and blocks to keep my material in place. If you're not going to use your machine as much as i do, using the machine itself with a keyhole router bit making inverted t slots in the spoilboard would probably be the simplest way. Then all you have to do is mill some cam type hold downs with a thru hole. Use a bolt to match the keyhole slot and a knob on top. If your material thickness varies much like mine does, elongate the thru holes. My 2" long oak holddowns can clamp anywhere from 1/8" to 1" material. For anything thicker i use a scrap piece and 1/2" thick maple blocks 1" wide. The screw or in this case, the bolt, goes between the material and the scrap block for the clamping action.
> 
> Best of Luck
> Randy


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## nigjoe (Aug 18, 2010)

Don't you have a vacumn table? If not you could make a spoilboard with an air vane recessed 1/4" groove and some rubber gasket material. Hook a shop vac up to hold the part down, may work for small parts with a minimal cut. For small acrylic letters I use double sided carpet tape on a piece of mdf.
Hope this helps,
cheers


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## Mark Sternberg (Jan 16, 2010)

Here is a neat trick that might work for you. I use a piece of 1/4" luan and glue it with a few dots of hot glue to the table then a few dots of hot glue to my work piece. It holds amazingly well and when you are done lightly pry the piece off the luan. The veneer on the luan will give way and come up with your piece then just cut it off or use a sharp chisel on your piece and your table. I use this method more than I use clamps that get in the way.


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## brtech (Jul 2, 2010)

Consider making the spoilboard in two parts. One is full sized to fit your table. On that, mount your T tracks, maybe 8-10" OC. Then put strips of spoilboard between the T track as a second layer. You can replace the strips when they become chewed up, but the T track remains bolted to the bottom part.


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## Metalhead781 (Jul 27, 2010)

brtech said:


> Consider making the spoilboard in two parts. One is full sized to fit your table. On that, mount your T tracks, maybe 8-10" OC. Then put strips of spoilboard between the T track as a second layer. You can replace the strips when they become chewed up, but the T track remains bolted to the bottom part.


Sounds like some great advice. I've since started using thinner material for a spoil board and just discarding it instead of running a surfacing program every few days. My problem is i've only got a small router on the machine so it's not like i'm using a 1 1/4" planing bit. Takes a while. Next chance i get i'm going to try the sectioned spoilboard and the t track. Something else i saw in lowes was a plastic track in the shelving isle that is a bit wide but may work as well. If by chance a bit does run into it you're not dulling it. 

Thanks
MH


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## roli_bark (Jul 17, 2010)

Thanks - that is a NEAT idea !


brtech said:


> Consider making the spoilboard in two parts. One is full sized to fit your table. On that, mount your T tracks, maybe 8-10" OC. Then put strips of spoilboard between the T track as a second layer. You can replace the strips when they become chewed up, but the T track remains bolted to the bottom part.


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## bobbya47 (Aug 4, 2010)

This works for me. Two pieces of 1/2" mdf screwed together from the bottom. Set up a program to cut a grid. I use 2" spacing. When it is done remove it and drill holes at each intersection . Take the two pieces apart and install 1/4" t nuts on the underside of the top piece. Counter sink the t nut heads using a spade bit. Screw them back together and reinstall on the machine. I made my own hold downs using 3/4" oak. Glue a small piece of sand paper to the contact points .I sometimes use just a flat 3/8" piece to give clearance where the router will run. Takes less than a hour to build. If it gets chewed up make another reusing the t nuts.


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## roli_bark (Jul 17, 2010)

bobbya47 said:


> This works for me. Two pieces of 1/2" mdf screwed together from the bottom. Set up a program to cut a grid. I use 2" spacing. When it is done remove it and drill holes at each intersection . Take the two pieces apart and install 1/4" t nuts on the underside of the top piece. Counter sink the t nut heads using a spade bit. Screw them back together and reinstall on the machine. I made my own hold downs using 3/4" oak. Glue a small piece of sand paper to the contact points .I sometimes use just a flat 3/8" piece to give clearance where the router will run. Takes less than a hour to build. If it gets chewed up make another reusing the t nuts.


I appologize for my late response. The idea of _*burried T-Nuts*_ is great !


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## richmad (Jun 1, 2010)

Buy or make a T-slot surface that can be placed on and off your tabbe as needed. Make your own clamps with slots and steps.
And/or you jig tape on a sacraficail surface such as sintra


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