When I purchased my wing kit, I went with the upgraded locking fuel caps, however, I didn’t have Van’s leave out the factory original non-locking fuel caps. One day I was talking planes with Kevin Faris and he had an extra Tru-Trak autopilot servo mount (and for the wing I wanted to put the mount in). So we worked out a trade, my factory fuel caps for the servo wing mount.

In the meantime, I got a CNC mill and decided that it would be nice to engrave these caps prior to giving them to Kevin.

I made a jig to install the cap into and hold during the engraving process. I used the test indicator to measure the corners of the fuel cap release in order to set my zero reference for “X” and “Y”. I also used the recess in the fuel cap release to ensure that the fuel cap was straight with the mill table so it didn’t look like the text was running up or down hill.

Just another shot prior to starting the engraving.

My spindle speed isn’t real fast, so my feed speeds are very slow. I used the mist coolant just to assist in chip removal. This was a learning experience for me to try and get the mill to center the engraving with respect to the fuel cap. Since it isn’t square, it took a different approach.

I think that these fuel caps are cast when they are made. If you look at the text, the text on the right is deeper than the text on the left. The “S” looks very shallow. The tops are not perfectly flat and the engraving is only around 0.010” deep, so any variation of the top surface makes a big difference when looking at the depth of the letters.

I tweaked the G-code by manually adjusting the depth of the engraver by 0.001” for each letter until I got a consistent look (depth) of cut for each of the letters.

Here is how the finished fuel caps turned out. When I was done engraving them, I polished them with an aluminum polish and stuck them in a vibratory tumbler for about 12 hours. This made a significant improvement in the look of the caps.

Fuel caps installed on N426KF.

The wive’s taking a break from poking fun at us plane geeks.