Spoil Board System

Brent Dowell

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So, now that I'm happy with my CNC Router, I wasn't really happy with my work holding. I had created a system a long time ago with 2 t slot tracks crossing the work surface in an X. It looked good, but in reality, all I did was to use some hold downs with it to hold a sacrificial spoil board on it that I would use screws on.

I used the sacrificial board because I didn't want to mess that 'nice' one up. All I ended up doing was robbing myself of 3/4" of z travel, and with my machine, I really didn't have that much to spare.

That worked fine, but it really wasn't all that convenient and constantly putting screws in it creates dimples that needed dealing with.

So I found this video and though, heck, that looks like it's worth a try.

He uses 3/4" copper tubing as a pivot point in pockets drilled in the spoil board to hold some lever action cams with some clever little blocks that give your 4 different clamping ranges that should be able to meet any side clamping needs.


I also went ahead and drilled a bunch of 13/64 holes in the board and tapped, then countersunk, and coated in super thin CA to harden them up a bit. I can use some hold down clamps in those holes to hold things down, if clamping from the side isn't good enough.

I'm using some purchased hold downs here, but I plan on making some that are a little lower profile out of wood that would not hurt the bit, should I make a mistake when planning cuts.

New Spoil Board.jpg
 
If you need to hold a lot of flat pieces to CNC them its a quick system. If you only need to do it from time to time I think it is overkill. Obviously having a CNC machine speeds the making of the cams and the board itself a lot, so that may convince many of those who have one.

Don't get me wrong, I think it is a great aid, but I'd raher use the time to make it in making a project if I will only use it scarcely.
 
I like it, very creative with a lot of basic workholding methods.

Nice system.

Jergens makes a workholding system similar to that to me used on industrial CNC metal working machines, but those systems can be thousands of dollars.

three things I noticed

1) I would not trust putting a piece of copper tubing in a hole and clamping against it. The tubing alone without the support of the wood can easily crush.

2) One of the wonderful things about the CNC is to do a profile cut around the outside, and make everything perfectly aligned

3) When cutting through all those nicely scribed lines will eventually get wiped out.

Other than that - it is awesome.
 
When cutting through all those nicely scribed lines will eventually get wiped out.

This is one thing that I'm researching on how to handle. I see a lot of people use a sacrificial board and 'skim' it from time to time.

What do you do for through cuts Leo?
 
I have a TEE SLOT table. The top has a rubber pad glued on. I do resurface the top every other year or so. It's due to be done. I don't really use it as a sacrificial surface but it does take a beating from everything else I do to it.

For a sacrificial top when I plan to cut through I have strips of 1/4 hardboard (masonite) that I put under the workpiece as needed. They are 4 feet long by 3 inches wide and 1/4 inch thick. If I am not cutting through I don't use them.

On my EX-machine I had a 24 x 24 x 3/4 MDF table with lines scribed into the top. The grooves were painted black and I Polyurethaned the top. They could endure 1 or 2 resurfacings and still keep the lines. After that I needed to rescribe but I had a program for that so it was easy to do. I basically screwed the workpiece down to the MDF. I used a drywall plane to scrape the dimples away.
 
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