Finished final/match drilling both tanks and completed the countersinking portion of the tank skins. No pics, because everything looks pretty much the same as it did earlier. Then we got started on the painful deburring process. Actually, we're putting off deburring most of the holes because we had a good friend and fellow RV-10 builder recommend a new tool I had somehow previously never heard of... something called an EZ-Burr (or competing brand Burr-away). The brand names sure sound promising! Basically, they are smooth pin-shaped bits about the diameter of the hole you're deburring, with a single spring-loaded blade protruding out from the shaft. The blade has a 45-degree edge on both the top and bottom ends. The way it works is, you run the drill down through the hole until the blade makes contact with the edge of the hole, and the bottom end of the blade deburrs the top side of the hole. As you continue into the hole, the blade compresses into the bit and allows the drill to go all the way through the hole to the other side, and then the blade pops back out. Then, with the drill still running, you can pull the bit back through the hole, this time deburring the bottom side of the hole with the top side of the blade. Brilliant!
Stock photo of the EZ-Burr bit I ordered
Between the EZ-Burr brand and the Cogsdill brand Burr-away, I decided on the EZ-Burr because it seemed to get better reviews about the design and ability to change the blades (allen screw vs. micro-size roll pin). Lots of options exist for diameter, blade angle, and rake angle, but I found an older post in the forums from an EZ-Burr rep who stated positive rake and 45/45 angles are ideal for the aluminum sheet we deal with. Also, 3/32" is a little too small for #40, but they also make a 2.5mm (0.0984") model that is best suited for #40. All of this research ended up with me ordering EZ-Burr models #EZL0098-02 for #40 holes, and #EZL0125-02 for #30 holes, along with a 6-pack of replacement blades that are compatible with both bit sizes. These things were NOT cheap, so hopefully they are the correct ones and work as advertised! If they do, I think they'll be well worth the cost in terms of time saved.
Anyway, other than that we're just slowly chunking away at the fuel tanks. Maybe we'll be ready for Proseal this weekend!