Broken headbolt

[StarTech]

Yes having a centering jig works best which would be great if I work on the same bolt pattern but I don't. Or if I did multiple engines with the same bolt pattern but again it more like one here and one there problem. If the screw is simply broken off from over torquing then a good left hand drill bit spins them out. It is those that are fused (galled) in place from excessive heat that are the hardest for me to get out and there is no easy way to save the threads either as that is what that is fused. I have seen screws so heat harden that only a carbide bit can cut them out especially when an extractor breaks off. Which I have quit trying to used as I broken several trying to remove screws; hence, that when the carbide bits comes out of the tool box as they are the only bit I know that cut those extractor bits.

Lately it has been the Kohler valve cover screws that are a pain which I just drill out the M6 screw and retap to M7 as there is enough metal to work with. It is not just head screws either as I have done exhaust studs and screws too.

I supposed I could take 1/2 a day making an one time use jig on the drill press but most likely I lose it before the next job a few years later. Also for the head jig it would be a lot easier if I had a spare to use while making the jig but normally I don't have a spare just laying either.

Just wait until you break off a tap as they shatter. I have tried those broken tap extractors but my luck they all broke instead removing the broken tap. I now know the secret of keeping a tap from binding in aluminum and it is not using cutting oil as that is just a bad as trying to tap dry.

I do however do a few jigs that I designed for mower work. I just design one for double D electric clutch retainers that is recessed. Just got to see if the aluminum holds or if got to make in steel. I am hoping that 65 ft-lbs don't destroy the aluminum version as a 2" steel blank is more expensive and a lot harder to mill.

 

[Hammermechanicman]

My jig is not bolt pattern dependent. It is a piece 1 inch square about 6 inches long with the holes in one end. I just lay it across the head with the hole i need centered over the broken bolt and i use another piece of metal across it and use two head bolts with it as a clamp. My farher was a millwright and taught me how to use a tap and die. I still have some taps he used when he was in the WPA. As he said " you gotta have the feel for it".
Of course there is the old trick to bolt the head on and use the bolt hole as a guide.

 

[PTmowerMech]

I finally got the broken stud out but there wasn’t enough material left in the case to chase up the old threads. I noticed that the headbolts actually terminates outside of the cylinder finns so I drilled the threads out and used a long grade 8 bolt and nut on it. So far, so good. A much better alternative than scrapping the engine. John

This would be a good one for this thread. "Happiness is."