Don't wan't to spoil my spoil board

I want to cut parts all the way through MDF but I want to avoid running tracks all over my spoil board. I know there are a few methods but would like to hear some best practices and ideas.

You need to do three things:

  • add a 2nd layer of surface board on top
  • Skim cut that (ensure Z is parallell with your XY plane
  • Use surface as Z reference, say you want to carve 5mm thin stock, use Z reference, jog 6mm up and set total carve depth = 6mm. This will maximize the precision of Z.

Hi there,

Me, I use a 1/8" piece of wood like used for pegboard. Its thin, flexible and easy to cut to size on top of my waist board and have yet to cut into my main waste board.

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While there are lots of people that will cut into their “spoil boards” and or resurface them, I have never been an advocate of doing this.
I have always considered it the “bed” of my machine, and as such it should be completely flat.
However, because of the inherent problems of movement with MDF, I have replaced my bed with aluminum fixture plate.
I ALWAYS use a piece of hard board under whatever I’m cutting to protect the bed. (I did this even before I replaced it)
My Z zero is always from the top of my work piece.

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I use a 1/8 piece of MDF as my pad for my cuts. Then after it has lived its life I use it for cutting stencils.

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Nice setup.

I’m looking to go to the aluminum bed as well. Florida humidity is making it impossible to keep the MDF from changing daily.

Take a look at ATP-5 cast fixture plate.
That is what I used for mine.
It has the same specification as Mic 6 plate but cheaper. (your not paying for the Alcoa name)
My whole machine is within ~.005"

Thank you.

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Jan, What is the price range?

Its been a couple of years but if I remember correctly it was around $250.00 ish.
I don’t know what size machine you have, but mine is a 750 and I still have the machine print with all the hole locations.
If anyone is interested I will gladly share it.


What thickness did you get?


I use Mr. Lonningdal’s method to zero my mill on the spoil board then jog Z up to a nominal thickness rather than trying to measure the actual thickness of the workpiece. I also use a sacrificial sheet of 1/4 MDF over the factory spoil board. I do not skimcut the sacrificial spoil boards for flattness because my machines are all three on mobile bases. Skimcutting them would be futile and because I make them oversized, skim cutting would eliminate the ability to cut oversized work pieces. I do have the machines on torsion box tables, so they stay pretty flat but I teach my middle school students to allow for about .030 out of plane over a 24" cut.

I’ve bolted my sacrificial spoil boards down with carriage bolts outside the carvable area. The bolts run through the spoil board and through MDF filler blocks thicknessed to fill the “frame space”, then through the tabletops that support the machines. They are secured from beneath with wingnuts treated with purple loctite so I don’t have to torque them down enough to distort the surface of the spoil board.

Once the sacrificial board is secured I run a carve routine that drills 1/2" holes to match the clamping locations on the factory spoil board, and runs a shallow grid pattern to give the kids an easy reference to the x and y axes to line up their work pieces.

What is skim cutting?
Can you explain this

can you please explain this as though I’m a complete idiot?
Also what is skim cutting?


Skim cut is an operation where you use your machine (with a large flat bit) to surface your wasteboard flat.
This ensure surface is parallell with Z as any minute height deviations are “skimmed” off.

As for my workflow when using surface of my wasteboard as Z-reference:

  • Jog my bit down to the surface, then jog it up the intended material thickness plus a little extra.
  • Use this raised elevation as Z zero
  • Set carved depth to same value (raised elevation)

This make a full depth carve to bottom out just at the surface of your wasteboard.

If you take 1/2" MDF for instance, and zero off the top of that - and carve 1/2" down you dont have full control of how deep it will bottom out/cut through as the MDF is never exact 1/2" thick.

I as well, like my spoil board to NOT be spoiled. Before I came across this, I found some real cheap obsolete color/design hard Pergo style flooring (planks) at Home Depot. An entire box of 9 pieces (9" x 48") sealed up in the packaging was like $12.00 I cut up a bunch of pieces/sizes to match the size of the project being cut. Simple and cheap.


thank you!