This is an old revision of the document!
IH: Engine Mechanicals - Sub-01A
Sprocket Cover Dowel Hole (Case) Repair
- This is a bit of an obscure one but a real pain to fix, requiring several special tools. This was also done with the cases assembled. If had split the cases I could have put them on my mate's milling machine and precision machined them. But because I was too lazy to split the cases and disturb that nice tight, factory original bottom end, I did it the hard way. 1)
- When it came back from the aircraft welder it looked like the pics below.
- Amazingly, there was no big blob of weld but two tiny little rings, still with the (rough) hole in the middle. His TIG welder can weld aluminum .010“ thick.
- The gearbox shafts and bearings were left in place during welding to help stop distortion of the cases.
- He pre-heated the cases gently with a torch and then he would put a ring of weld on, let it cool off, repeat, repeat repeat etc.
- Notice how he welded around the screw next to the top hole but did not go over it. And the 1/4” threaded hole in the middle was still useable.
 |  |
- Now all I had to do was re-machine those two 7/16“ dowel holes back where they should be within app. .001”.
- First thing was to file the flat surfaces back on again, using the sprocket cover with bearing blue on it as a guide. A couple of hours with a pair of 10“ bastard file and millsaw file did that.
| Here's a drill jig made from a half-inch steel plate to guide the drill |
 |
1)
Hopper of the XLFORUM http://xlforum.net/forums/showthread.php?t=395586
