Not Model Engineering as we know it!
Have just reinstalled the air compressor for the church door opener.
Last week it started "tinkling" instead of delivering air. Since replacement would be circa £800, a pal and I thought we had nothing to lose, and opened it up. Looks like a fridge compressor, but top is clamped on, rather than welded. The bolt holding a sort of welsh washer in place had broken; flush with the bottom of relatively small, deep, bore. To make matters worse, the bolt head was stamped "12.9". And it was HARD.
Turned up a tight fitting bush ready to start trying to drill out the remains. Disconnect compressor pipe and mains cable. Clamp to table of Mill/Drill and after two broken drills, (one a carbide tipped one!) finally removed the debris, at the cost of some damage to the casting. Once eventually out, progressively drilled the casting until it could be tapped 1/2" x 40 tpi ME, interspersed with repeated use of magnet and vacuum cleaner to remove the swarf. Turned a piece of BMS to 0.500" diameter and used a die to give about 0.300" thread length. (would have liked more, but frightened of breaking through casting). Trial fit and mark top of bore. Part off to 0.250" less, face, drill and tap for 1/4 UNF, (to match existing hardware)
Trial fit to check that the blanking washer will be clamped. Clean rust and dirt off all everywhere. Loctite 1/2 x 40 thread, and screw hard into place with long 1/4UNF setscrew and nut. Remove the improvised stud box. Hylomar sealing face of plate and underside of head of new short setscrew, and tighten down. Test before connecting to reservoir, and it delivers compressed air! Reconnect to reservoir, and return to the church door.
After correcting a minor leak, it will open the door four times on the contents of the small reservoir before cutting in again, for just under 10 seconds. Then find GRP cover is squashing the nylon delivery pipe; so butchered to make a slot for the pipe, and now the mains lead.
Come home and search for CDM to award myself! Still looking; but a satisfying end to two days of slow work.
Howard
Edited By Howard Lewis on 27/01/2018 17:43:09