Description
Here is the situation. You have drilled out an existing 1/8″ rivet, replaced the material underneath and now you need to match the existing rivet hole into the new piece. Especially on thin top skins such as .025 or thinner, the point of a 135 degree split point #30 drill touches the new part underneath before the edges of the drill touch the sides of the existing hole. So now you start drilling and realize you are not quite centered. The only way to get this hole back on center is to angle the drill to work the hole back, but now it does touch the edge of the existing skin and you have a mess in development.
The only option is to drill the hole larger yet to get the proper fit. This is not only ugly, but potentially dangerous as each rivet needs an accurately sized hole to carry its shear load.
We have developed a tool that allows a precise alignment of a pilot hole. We take a normal #40 drill bushing and precision grind the last 1/8 inch of length to a .125 diameter. This fits perfectly in a 1/8″ rivet hole, even on a .016″ skin.
We mount the modified drill bushing into a piece of precision machined, super tough clear polycarbonate so you can see the tip to accurately place it in the hole without the possibility of scratching the surface by moving the tool around until it drops into the hole. We secure the drill guide in the polycarbonate handle with a soft tip set screw to hold it in place so you can have the 1/8″ end sticking out just enough to engage the top layer of skin, while holding it perpendicular. Now that a #40 pilot hole is accurately placed, the final #30 drill can drill it to size.
