More with the broken bolts already !

Charles in Aus. · Jun 21, 2016

There must be a virus going about

A friend's 17 year old son has an off road motorcycle with a broken rocker cover bolt . The shank is only 5mm and of course it is a few mm below the surface , it is surrounded by alloy castings and is stuck in the alloy head .
Heat is out of the question for fear of ruining the alloy , 5mm seems a little too small for a screw extractor and then there is the problem of just how to get the hole drilled into the exact centre .
A left handed drill comes to mind but I have never seen let alone used one , any tips for using one ? Any other suggestions gratefully received .
This is a good' hard working and deserving boy and I would like to help him out if I can .

Geo-TH,In · Jun 21, 2016

I bought a set of left handed drill bits, form Wal-mart in the as seen on TV isle. Never used them yet, so can't tell you anything about them.

Bob Bancroft · Jun 21, 2016

40 years ago I spent day after day in a corner working on chainsaws. I can't remember the details, but this sounds like a similar problem.

What I recall-

I would make absolutely sure I was drilling in the center. Start with a puncture wound/center punch. Drill a little and look at it. Angle the drill as necessary to push the hole to center. Use a small bit, and drill all the way down through the broken piece, before going to a bigger bit. Then sometimes you could get a "bite" with a bigger, left hand bit, and back the piece out, but that was rare. Seems like I usually ended up just drilling the piece out, and tapping the hole. As I recall, I was usually successful. But "Heli-coils" were a must have the rest of the time!

Jaden · Jun 21, 2016

If drilling them out, and they are broken off below the surface, a transfer punch will help center the drill. Mark it with the transfer punch, use a regular center punch, and then drill. Left hand drills, transfer punches, are available at good old Harbor Freight.

chuck2015 · Jun 21, 2016

(quoted from post at 03:41:27 06/21/16) There must be a virus going about

A friend's 17 year old son has an off road motorcycle with a broken rocker cover bolt . The shank is only 5mm and of course it is a few mm below the surface , it is surrounded by alloy castings and is stuck in the alloy head .
Heat is out of the question for fear of ruining the alloy , 5mm seems a little too small for a screw extractor and then there is the problem of just how to get the hole drilled into the exact centre .
A left handed drill comes to mind but I have never seen let alone used one , any tips for using one ? Any other suggestions gratefully received .
This is a good' hard working and deserving boy and I would like to help him out if I can .

My opinion but a good machine shop should be able to remove the 5mm bolt without too much problem. JMHO

Dick2 · Jun 21, 2016

They don't have Harbor Freight in AU.

jon f mn · Jun 21, 2016

Most left hand bits are cobalt or at least very hard so be very careful not to break it off. That makes
for a mess. I'm sure the aluminum or magnesium has corroded to sieze the bolt. Before you center punch
it give it a couple whacks with a punch to try to break it loose.

Steve@Advance · Jun 21, 2016

A lot depends on why it broke. If it was over tightened, or sheared off, it might can be "picked" out with a small punch. a left hand drill might spin it out, or an ez out, but be careful not to break it off.

If the threads are seized, or the bolt is bottomed in the hole, it will have to be drilled out. Best done in a mill if the part is removable. Hand drilling a bolt that small is difficult, but can be done if it's accessible.

When looking at the end of the broken bolt, what appears to be the center really is not! Take in consideration you are actually viewing the peak of the thread on one side, the root on the other. That needs to be considered, especially on a small bolt, it's that critical to find the center!

A drill guide can help keep the drill straight. Drill a known straight hole through a thick steel block, secure it to the flat surface with an adjoining bolt, locate the hole over the broken bolt.

Dick L · Jun 21, 2016

Exactly as what Steve said:

Dick L · Jun 21, 2016

Exactly what Bob and Steve said: Nothing I could add.

dr sportster · Jun 21, 2016

Snap-On has a good extractor kit for that but I don't have a link. One weird way I have done that is drill all around the broken stud with tiny drill then pull out piece and heli-arc in the whole hole for heli-coil. Depends how much the engine is worth on how much time you want to spend. Sometimes if you can drill all around and get the piece out no welding is required as the heli-coil drill bit is slightly larger than the original tap drill . The extra diameter allowing for the thickness of the heli-coil.

IA Roy · Jun 21, 2016

First I would try using abundant amounts of Black Silicone Caulk between the cover and the head. With the remaining bolts, that might take care of things. Unless there is more pressure (crankcase) behind it than I think. An inexpensive and quick fix if it would work. Of course clean the mating parts completely and give it at least a day to cure.

bison · Jun 21, 2016

(quoted from post at 03:41:27 06/21/16) There must be a virus going about

A friend's 17 year old son has an off road motorcycle with a broken rocker cover bolt . The shank is only 5mm and of course it is a few mm below the surface , it is surrounded by alloy castings and is stuck in the alloy head .
Heat is out of the question for fear of ruining the alloy , 5mm seems a little too small for a screw extractor and then there is the problem of just how to get the hole drilled into the exact centre .
A left handed drill comes to mind but I have never seen let alone used one , any tips for using one ? Any other suggestions gratefully received .
This is a good' hard working and deserving boy and I would like to help him out if I can .

f that bolt is broke of below the surface then good luck in trying to extract it as the top treads are probably ripped up. If there is enough meat for a slightly thicker bolt then i would drill it out with help of a guide to keep the drill straight and centered over the hole and tap for the next size like a 1/4" standard allen head bolt

Charles in Aus. · Jun 22, 2016

Thank you all for the suggestions . We don't know how it actually broke , it was that way when it was given to him , he is going to remove the engine for me so that we can get to the bolt without interference.
Once it's in the workshop I'll let you know how it goes .
Am I right in thinking that left handed drill bits are used with the drill in reverse ?

Traditional Farmer · Jun 22, 2016

Yes you use the drill in reverse to use a Left hand bit.The real trick to getting a sunken broken bolt out is to be able to center punch a hole exactly in the center of the
bolt then,I usually drill a hole about 1/2 the diameter of the bolt in the center of the bolt then drill out a larger hole with a left hand bit usually the 2nd drilling
backs the bolt out.Probably because of the heat from the 1st drilling and the relieved pressure on the threads.If it doesn't come out then I drill a hole just where I think its barely inside the threads and go to work on it with a bottom tap and maybe very carefully with a small sharp chisel.

tx68 · Jun 22, 2016

Would the alum method work.
Here is a utube video showing one way to do it.
Untitled URL Link

Charles in Aus. · Jun 22, 2016

Some photos of the offending bolt ,

I tried filing the shank of the broken one and it appears to be very hard .
I was greeted by idiot stares from the young man when I asked for a left handed drill at the local tool supplier . I might as well have asked for a bubble level , a long weight or a left handed screwdriver .
I told him he was an idiot just before the manager came and gave him a figurative boot up the bum .
It does turn out that they are quite a rare thing here and cost $65 Aus each for small sizes !
I am going to try the punch first , a small brass ferrule will fit into the hole and might centre it correctly . A dremel with a diamond tip might just be able to bore into it , especially if it is only case hardened .
Other than that it might have to be a job for an expert . The trouble is since almost everything in Australia is made in China there are just no small engineers or jobbing workshops left .

Charles in Aus. · Jun 22, 2016

That truly is amazing TX , is it for real or some You tube trick ?

bison · Jun 24, 2016

(quoted from post at 20:10:35 06/22/16) Some photos of the offending bolt ,

I tried filing the shank of the broken one and it appears to be very hard .
I was greeted by idiot stares from the young man when I asked for a left handed drill at the local tool supplier . I might as well have asked for a bubble level , a long weight or a left handed screwdriver .
I told him he was an idiot just before the manager came and gave him a figurative boot up the bum .
It does turn out that they are quite a rare thing here and cost $65 Aus each for small sizes !
I am going to try the punch first , a small brass ferrule will fit into the hole and might centre it correctly . A dremel with a diamond tip might just be able to bore into it , especially if it is only case hardened .
Other than that it might have to be a job for an expert . The trouble is since almost everything in Australia is made in China there are just no small engineers or jobbing workshops left .

would take the cylinder head off the engine or you get all the chips in the engine.
That way you can clamp the head in the vice in the drill press and might not need a drill guide. The bolt is probably metric 10.9( similar to grade 8 standard) The bolt was most likely over tightened and stretched before it broke, if that is the case then the stub could be hard to extract as the top treads of the stub are also stretched and seized in the aluminum treads. As i suggested in a former post your best bet is to drill the stub out with a drill seized for 1/4' standard tap.I would start with a drill bit that fits snug in the exposed bore to get a centered start on the stub and then drill to dept with a 1/8" bit, use a slow speed(or stop and go, stop and go) as the bolt may be hard to drill and speed will just burn the bit and case harden the stub even more(use cutting fluid) drill the hole bigger in increments, don't try to take a big bite at once. You have only one go at it so do not screw up by hurrying,..easy does it.

Charles in Aus. · Jun 24, 2016

A big thank you for all of the helpful and informative comments .
The bolt is now out ! What a little B@$t@rD .
I first used a brass collet that fitted snugly into the hole , mindful of the warning to get the dimple in the exact centre of the stub .
With the collet as a guide a carbide burr put a small hole close enough to be able to follow it up slowly with a 2mm drill .
Slow and steady as I was warned to I used cutting oil and care . Denso tape covered the exposed engine parts to stop chips getting into parts they shouldn't , another timely warning .
An easy out used gingerly at first got it moving as far as the top of the hole where it started to tighten up due to the torn threads . Once more a warning well made , a small punch as suggested got it moving again . I did this five times in all gaining a thread or two at a time . Out it came , no thread damage and little sign that there was a problem at all .
My friend's son is ecstatic , straight off to the shed to reassemble it . I decided to buy him the new bolts and a gasket set so he won't be tempted to over tighten it to stop leaks .
Thanks again all .

bison · Jun 25, 2016

Congrats,..job well done.

More with the broken bolts already !

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