Vacuum Hold Down on a CNC: Cutting a Birch Plywood Footstool.

October 7, 2026

I made this footstool as a gift, and it turned out to be a good excuse to show how I hold plywood down with vacuum instead of clamps. Everything was cut on my Onefinity CNC.

If you've wondered what vacuum workholding looks like on a small home machine, this is a pretty typical day in my shop.

Why vacuum instead of clamps?

Clamps work, and I still use them. But on a job like this one, vacuum makes a few things easier.

Nothing sits in the toolpath. With clamps, I have to plan around them so the bit doesn't run into one. With vacuum, the whole top of the sheet is open, so I can cut right up to the edges.
Setup is quick. I set the plywood down, find my corner, and I'm ready to run. There's no tightening, no checking that each clamp is square, and no worrying about one working loose.
The hold is even. A clamp grips in one spot. Vacuum holds the whole underside of the board against the table, which helps keep a sheet flat while you cut it.
It's gentler on the wood. There are no clamp marks, and no pressure that can bow a thin or already-cut piece.

There are trade-offs though. Vacuum works best with material that's flat and fairly nonporous, like this birch plywood. It also needs a pump and some kind of gasket or spoilboard setup, so it's more to buy up front than a handful of clamps.

If you're not sure it's right for you, I'd start by thinking about what you cut most. If it's a lot of sheet goods and flat parts, vacuum is worth a look. Here are the AirWeights vacuum panels I use.

The footstool design

The footstool is a product made by Brandy, who goes by @HandyDandyBrandy in Instagram. She sells finished stools, and she also offers the design files for personal use.

If you'd like to buy one or make your own, I'd encourage you to head over and support her work.

I made a few changes to the design. The main one was adding dogbones to the pockets, which are small corner reliefs that make the parts go together more easily, but the original design goes together great as well. It also includes a pattern for socks, which you can add if you'd like.

The material

I used scrap 3/4" birch plywood left over from another project. I set it on the vacuum table and found the corner of the stock to set my starting point.

Birch plywood works well for vacuum because it's flat and fairly nonporous. Both Really important for a vacuum setup.

How the vacuum setup works

I didn't use fixture clamps. Instead, I use an MDF panel with a sheet of tile gasket on top, which mounts to my AirWeights vacuum panels.

The gasket is covered in small holes, and each one acts as a little vacuum pocket. As long as your material is flat and fairly nonporous, it grips firmly with no extra clamping.

I'm running two 5 CFM AirWeights pumps for this project. One is usually plenty for my work, but the second gives me extra holding power for a job with this many cuts.

Covering the unused gasket

Once I moved on to the smaller wood panels, they didn't cover the whole gasket plate. I laid a piece of acrylic over the exposed area.

You want all of your vacuum working on your stock, not leaking out where nothing is sitting.

The bit and the cutting strategy

I cut in three step downs. That means the machine takes the depth in three passes instead of one, which keeps the sideways force on the material low.

For the endmill, I used a Cadence Manufacturing 1/4" compression bit. It's a good fit for plywood because the tip cuts upward and the rest of the flutes cut downward. That gives you a clean edge on both the top and the bottom.

Leaving an onion skin

I leave a thin layer of wood at the bottom of each cut, called an onion skin. Mine is only 0.02".

It keeps the pieces connected to the sheet, and it keeps the full area of the part under vacuum so the hold doesn't drop as the cuts open up. It snaps off cleanly, and it sands smooth.

From there, it's rinse and repeat for the remaining pieces.