Leveling Insert Plates

I wasn't satisfied with the way the sacrificial insert plates sat in the recess on my drill table. My original plan was to use 3/4" MDF plates, the same width as the top layer of the table. As I later discovered, not all 3/4" MDF is the same thickness. I'm not sure if it's variation between sheets, or that the smaller pieces of the MDF are less stable with temperature and humidity variations. No matter the cause, I couldn't get new plates flush with the surface of the table without a lot of material removal -- even then it wasn't perfect.

I decided that the only way I'd get the plate level was to build some sort of leveling system into the table. After weighing the options I decided to use screws and jam nuts.

The first thing I had to deal with was that I didn't leave much room for any adjustment mechanism when I built the table. The opening in the bottom sheet is just smaller then the plate opening by a 1/4" or so. That means I had to use some pretty small hardware. I decided on using 6-32 screws and inserts because they were the smallest I could find locally.

Rather than using threaded-inserts that you drive into the surface, I found some hex drive inserts that you screw in with an Allen wrench. I drilled holes that where slightly larger than the barrel of the insert so the threads would have something to grab. Several of the holes were so close to the edge that the sides were open. There was still enough material so the inserts stayed in place.

 

I placed a nut on top of the threaded inserts before screwing in the flathead 6-32 screws. The nut acts like a jam nut so the screw won't turn except with a screwdriver.

 

 


This is just a better view of the screw and nut assembly. The plate sits on top of the flathead screw. If the plate is too high, you just tighten one or more of the screws. If it sits too low, loosen one or more screw.

 

With the height adjustment hardware in place, I can no longer use a 3/4" plate, so I cut one out of a sheet of 1/2" recycled plastic I had lying around. It's soft and consistent. It also shouldn't change with the ambient conditions. One advantage of this material is that I'll be able to see when I've drilled through, because black plastic will start coming out of the drill flutes.

 

With my table top completely flat, I just need to figure out how to get the table to stop flexing when I have to apply moderate to high pressure on the quill and maybe I'll be able to drill straight into the end of a dowel.

Tools: drill press

Tags: jam nut, leveling

Materials: MDF