Breaking 6-32 Taps

Breaking 6-32 Taps

I decided to use a total of 9 6-32 screws to hold the spider legs to the diagonal holder. I used the vertical mill to very accurately drill the holes--and then I broke two 6-32 taps trying to tap the holes. Maybe I didn't use enough thread cutting oil when doing this, or maybe tapping 6-32 holes in aluminum is just asking for trouble. Anyway, since I now had two pieces of aluminum with broken taps in them, I gave up, and made the next piece of Delrin. It machines easier, and is still adequately stiff and strong. I also switched to 8-32 screws on this one because I had run out of 6-32 taps.

Since there will be three legs on the spider, how do you get the holes exactly 120 degrees apart on a cylinder without a rotary table on your mill? Since I have a 1/4"-20 hex head bolt going through the length of the cylinder, this was pretty easy. I used a right angle against the hex head bolt's edge. Each rotation of the face moved the cylinder 60 degrees.