Re: John's 1935 1201 Coupe for Two or Four Passengers, RHD in Tasmania

Posted by DavidM On 2018/5/10 4:22:52

John,
In order to drill out those broken studs you will need to centre punch each one exactly on centre and that is extremely difficult . In addition you will have your drill exactly square to the face, that is easy providing you make a simple drill jig.
You can make the drill jig using a piece of say 1/2" round with a 1/4" or 3/8" thick flat welded about square to the end. Then fit the round in a lathe, face off the flat and drill the round to the diameter of the drill you intend using. This is then clamped to the face of the block to align the drill squate to the face. The drill will be smaller than the 1/4" diameter of those broken threads. You may need to drill increasingly larger drill sizes and you can enlarge the drill jig to suit as you go. If you have drilled on centre, with a bit of luck you will get the stud out. Don't try to get it out with one of those tapered left hand thread stud extractors or you may end up with a broken stud extractor which is a whole new problem.

Before using this approach I would get a nut the size of the broken stud and weld it to the end of the stud, not easy with such small threads but it can be done. There is an excellent chance that the heat will loosen the broken stud and you will be able to unscrew it out with the nut.

On one of my cars all of those threads were in such poor condition I heli-coiled the lot.

.