drilling out a stud in an engine 31 October 2007 at 5:11PM in Motoring 8 replies 710 views

fatblokexl

what is the best way to do this as to not damage the engine?

hartcjhart

more info please,where,what size,access etc

fatblokexl

its on a scooter, direct access (if i can get the bike high enough off the ground).

its the exhaust manifold stud, sheared in the engine block.
approx 5ml diameter

Wig

The best way, as it is a scooter would be to remove the engine mount it in some form of frame which will render it unmoveable, use a pedastal drill with tungsten carbide drill bits. Start with a bit 1mm diameter, to make the first hole in the centre. Try to be bang on in the centre, if you can't becuse of the way it sheared attack the centre point at an angle for the first 0.5mm then straighten up and attack in the same hole from a vertical position.

when you have made the first 2 - 3 mm of hole you can change to a 2mm bit and go a bit deeper, change to a 3mm bit and best to use a left hand drill bit.

Now you can try a reverse thread screw extractor, but be very careful don't exert too much force or you could snap the screw extractor and you might not get it out the hole, and there's no way you will be drilling any further.

I don't think you will be able to move it because it snapped off in the first place meaning it is well and truly stuck in there. So ultimately you will have to drill the whole stud out. Check the other studs/stud holes for length, so you know how deep you have to drill and keep increasing the drill size (and trying a larger screw extractor) until you are just inside the thread on the cylinderhead, then you can pick at the shavings of metal in the thread grooves and you are done.

If you did not get the drill absolutely vertical you may find you drill into the thread walls. You will probably have to cut yourself a new thread using a thread tapping set.

hartcjhart

exactly what I would have said,

Wig said
Now you can try a reverse thread screw extractor, but be very careful don't exert too much force or you could snap the screw extractor and you might not get it out the hole, and there's no way you will be drilling any further

very true:mad: I did it myself once ended up having to take engine to a machine shop

slowly slowly little by little is the way

Wig

Or if your screw extractor is snapped off, you give up and leave that stud in there, and hope that the exhaust doesn't blow.

But on a scooter he probably has only got 2 or 3 studs, so leaving one missing is not going to work.

steveo3002

can you push it to a engineering shop at all?

they'l be used to doing this kinda stuff all day long and will stand less chance of messing it up, prob cost the same as a good drill bit and the easy outs etc...i.e under £20

goldspanners

im guessing you cant get it with a hammer and chisel?
i get this problem a lot,soak it with wd40 (or similar) leave it for a bit,and then try taping it witha small sharp chisel,this has got me out of a few holes in the past.
other wise try the drilling as the others said from 1 mm up,you may find if you get to the 3 mm drill bit you can then get it out with the hammer and chisel as it will have heat up a good bit by then.

good luck.

epninety

Northern Tool sells a set of left handed drill bits for about £25. They aren't great quality, but they are a bargain at that price. It's amazing how often a seized bolt or screw will unscrew while you're drilling it out.

If the break is fairly flush, I'd try 'puddle' welding a nut or a flat bit of bar (with a hole drilled in it) onto the broken stud. Often the heat of welding will break the corrosion which stick the stud in place, and you can just unscrew it after welding.