removing broken studs

I'm taking apart, before reassembling, a MKIII Roadster. I have encountered two problems, both being broken off bolts/studs - below where I can grab them with a vise grip or cut a slot in them.

One is in the right side (non-disc) fork leg, it's one of the two studs that would be used to mount a fender.

The other is for the points cover.

I would like to try and repair myself before going to a machine shop. Looking for helpful hints.

Steel bolt in aluminum housing obviously means I need to be careful. I found on here a suggestion to use a dowel fitted into the hole to keep a drill bit centered. What sort of bit should I be looking for to drill out a steel stud/bolt? Should I oil it as I drill, or ???

Regardless of the type of extractor used, get your self some Corrosion Block and put it on the screws. Then heat the area with a heat gun. The alloy expands at a faster rate than the steel and this help pull the fluid into the threads. On alloy cases that have been negected for a number of years. I do this on all the screws before attempting removal. It has proven to be worth the effort.

I really like the extractors that have a reverse drill bit built into the extractor. Often after the above operation, the drill will back out the screw without having to bite. You can repeate the lube and heat until you have success, and heat it while trying to remove the screw too.

Good luck,
Russ

When one of my screws in the timing side was broken, I didn't even have to heat anything up. All I did was WD40 the hole, then I used an ice pick to try and spin the screw out. Worked, as they say in England, like a treat.

Above suggestions should work 90% of the time, Ie: pentarating oil/wax, heat cycles and tiny extractors or dental tool lock picking. If stud is over 1/4" dia. I've have shop put a nut over the sunken stud and weld fill hole then wait 30 sec and twist it right out, while Al still greatly expanded locally. But If jammed in d/t the shearing that initially broke them, or rust so expansive, its not free to turn even after some turning grip gotten on it, then might consider dissolving the steel away from the Al via nitric acid or other faster acting strong inorganic acid or longer acting weaker organic acids, acetic/vinegar for instance but also in molasses. Steel turns to redish-mushy-paste, to flush out and repeat until jammed parts gone or stud a nubbing that just falls out. Hard steel broken off extractor bits may need chemical assist. There are electro ablative methods that hi end shops offer. Strong alkaline detergents can dissolve off head fins in one wash cycle, but not strong acid attack.

Once the holes are free of broken fasternes and/or the steel extractor parts, the thread may be trashed, so I've had success with fairly strained TS case screw repair using the epoxy thread re-creating repair kits. Specs are higher than the Al threads.

Get yourself a set of left handed drill bits and stud extractors like these.
http://www.ebay.com.au/itm/10pc-SCREW-E ... 1560wt_698
If you are any good with a drill, used in reverse, you should be able to get a hole started in the center of the broken stud. After center punching first preferably. Apply lots of lube and quite often the left handed drill bit will pull the broken stud out.

in small dia. shallow holes you better use a drill press or milling machine as no way can hand held keep the drill bit from wondering into removing threads as much or more than steel stud. Remember about the epoxy thread repair kits...

for smaller screws I've had variable results with tapered spiral extractors, but I seem to do OK with cheap Torx bits hammered in.
The tapered extractors can expand the screw into the alloy making the job more difficult.
Over the years I've found that anything will move once hot enough :wink:

Thanks all.

The idea of a guide for the bit in the fork leg is very valuable as the broken surface is not flat. Well all the ideas deserve thanks, so THANKS :!: :!: :!:

I'm slightly ashamed to admit on the timing cover my memory was bad. It seems the lower pillar bolt slips in and out of the timing case - perhaps the PO overtightened the bolt? Anyway, the problems are not the same as I inadvertently led you all to believe.

So, one stud to be extracted (heat, something to break up any corrosion bond, and a bit guide block with some left hand bits). I know nitric acid has essentially no effect on pure aluminum, but I'm more than a little worried about the alloy composition to try anything too exotic.

Timing case I expect to now remove and investigate methods of restoring threads - anybody care to comment on the Permatex two-part epoxy thread repair kit? Since the load is so low I don't see why this wouldn't work, but then again I've never used this sort of product, so...

As I remember that timing cover is a 2BA, so it should not be hard to find a 10/32 helicoil insert to put in it. If you did one, I'd do the other. If you use Allen heads, I doubt if anyone could tell the difference. But if you're a purist, maybe you could find a 2BA helicoil. I know Steve loves JBWeld, but I've never had good luck with it except for bedding receivers in stocks.

Dave
69S

I'm not a machinist, just a hand driller bench grinder level but sleep in cheap motels or on the ground so depend on these now and then to get going again.

http://paint-and-supplies.hardwarestore ... 13340.aspx


Rockler Woodworking Accurate Drilling Without a Drill Press
http://www.rockler.com/blog/index.cfm?m ... 7D26277FE0

A few years ago I low-sided my Interstate and ripped off the points cover. I tried the permatext thread restorer, but the vibration seemed to cause it to break up. I have never had great luck with using a 10-32 helicoil for a 2BA bolt so I tried a 2BA helicoil (Australian made) but it stripped the threads on the soft pillar bolts. I finally gave up and drilled and tapped the cover and turned an aluminum dowel, threaded the outside the correct oversize for the hole and loc-tited it in. I then cut off the dowel flush and drilled the dowel in the cover and tapped a new hole the correct 2BA size. It took less time than screwing around with the helicoils and thread restorer.