Finished the casing today. It is 1780mm long and will hold 12 BATES grains. Important factor in long rockets is that all parts being properly aligned. To facilitate this all the tubes (casing, airframe & nose cone) rest on square faces. As I didn’t want to rely on the squareness of the band saw cut I had to square off the ends of the casing. However I don’t have a steady rest which can accommodate the 86mm tube and didn’t want to spent the time (yet) on a DIY steady rest. Therefore I outsourced this to the machine shop at my work. They had a lathe with a 100mm ID spindle to directly clamp the tube it in and machined it to length. Now it is perfectly square.
For indexing the countersunk M5 bolts I reverted to my indexing technique by fixing a small indexing head to my lathe and an expandable mandrel clamped into the hollow spindle of my lathe. I have a laser cut custom tool, made out of 10mm steel plate, for an electric drill with a 43mm collet which mounts to my quick change tool holder. On the the lathe:
- Center drill,
- 4mm tapping drill (approx. M5)
On the column drilling machine on the slowest speed possible the counter sinking was done, lubricated with plenty of ethanol.