I recently made this 14” x 11” plaque for my daughter and while it turned out OK, it did have some issues. If you look closely, you can see some marks made by the end mill when the center of the stock bowed up a little during the engraving operation.

To solve the bowing stock problem, I decided to make a vacuum fixture to hold the 14” x 11” stock.

Here the fixture is mounted on the KRMx02.

Here the same fixture is mounted on one of my CNCCS machines.

The fixture is composed of two components with the bottom portion of the fixture shown here.

On the bottom component, all the features are 1/4” deep forming vacuum channel.

The small holes along the outside are pilots for the screws that will be used later to attach the top component to the bottom.

The top component shown here consists of several 3/8” pockets 1/4” deep with a small hole in the center going all the way through.

There are also some smaller 1/4” pockets along the left and lower edges. The can be used to insert some wooden pegs to help align the stock.

The pilot holes along the outside edge have countersunk pockets to keep the mounting screws away from the surface of the fixture.

Bottom Drawing File

The small holes are .126 in diameter so you can use a 1/8” end mill to mill the holes without having to peck drill. Much easier on the bit this way.

The vacuum channels are 1/4” deep and will line up with the holes in the top component.

Top Drawing File

The pilots along the outside are .126 in diameter and go all the way through.

The countersunk pockets should be milled first to make these small holes easier on the bit.

The vacuum holes and pockets are done the same way.

The shop vacuum port should be sized to fit an elbow to use with your shop vacuum.

I insert 1/2” tabs and leave them untrimmed to keep the elbo from moving into the lower component pocket.

I have a complete set of drawing files available for purchase. The set includes AI, DXF, and EPS formats for three different sized fixtures.

15” x 16”

14” x 18”

15” x 26”

29” x 26”

Get the set here:

Full Set of Vacuum Fixture Files

or here:

Full Set of Vacuum Fixture Files

I make the bottom fixture first using a 1/8” spiral bit.

I used these:

set of 10 1/8” Carbide End Mills

I cut these at 100IPM with a DOC of .0625. I also used a .1” plunge ramp at the same speed.

The top comonent is completed with the same end mill and again a light sanding is done to clean the small frayed edges of the MDF.

Place the fixture top component on top of the fixture bottom component. Secure the top to the bottom using 16, 1/2” #8 wood screws.

The mounting holes should self align the fixture components.

I recommend using a clamp next to the screw holes to make sure the top is tight against the bottom. Don’t over tighten.

When you add the four center screws, press firmly on the center as you tighten the screws.

If you want to add an easy reference for the stock, insert some 3/8” dowels into the 1/4” holes along the left and bottom edge of the fixture.

These are not glued so that they can be easily replaced as needed. The dowels will place the stock exactly 1/2” from the left and bottom of the fixture.

With homing switches, and a fence, just set the X and Y DRO’s to .5 and your stock will be all set and ready to engrave.

Notice how I left the holding tabs on the top component vacuum port hole. This will keep the shop vacuum elbow from bottoming out on the bottom of the bottom component.

With the fixture assembled, you may want to surface the top of the fixture, thus ensuring it will be perfectly flat. This is important if you will be machining the stock over some sort of gasket material.

With the elbow inserted into the vacuum port, the fixture is ready to use.

I have used the fixture to make a couple small engravings and even with smaller parts like these, it has enough holding power, even with my vacuum set at its lowest suction setting.

When engraving smaller stock, you will need to block the unused holes. Here I am using some scrap craft foam for this.

Here I am holding a piece of aluminum stock in place. I would have no problem machining this stock with only the vacuum holding the part.

With the shop vacuum at full power, I think the clamps holding the fixture would give out before the vacuum failed.

Here the fixture is holding sheet of gasket material for drag knife use.

MDF is porous and will allow some air to flow through it. This air does not seem to affect the performance of the fixture. On lower end shop vacuums (shop vacuums without separate cooling ports) you will need this extra air movement to keep from burning up your vacuum.

If you want to seal the MDF I recommend adding contact paper to the bottom of the fixture.

Most of the time when I am working on a project like this, i will take videos in hopes of creating some content that will help folks out.

Here is the video I made from this project.