Help - rounded Allen bolt

[voodoorider]

Okay, so I'm finally disassembling my fisher CR7 to be powder coated.... For those that don't know the frame the Steel rear triangle is bolted to the front al triangle.

I've got 3 of the 4 bolts out... Of course the 4th decides it won't budge and then then rounds the Allen bolt. This is the one In the bb which only has a hole to access it, looking for suggestions on a plan of attack.

Is it best to just drill the head out that should release the rear end of the frame and then i can go at to get the remainder of the bolt out...suggestions... With some 20 yo loctite it's in there pretty good.

 

[Woz]

Drive in torx bit with a lump hammer.

 

[mattr]

Then use some heat on the shaft to soften the loctite, and loosen the bolt.

If that doesn't work. It's drill time.

 

[voodoorider]

Hmmm I'd seen that online, the challenge I have is that the only access to the bolt is from a hole in the bb directly across from that is maybe 10 or 15mm diameter, let me see if I can attach a pic to my original post.

 

[voodoorider]

Photo added, you can see the access I have.... Either through that hole in the bb or through the bb itself.

 

[daugs]

Drive in torx bit with a lump hammer.

trouble with that is if the torx bit breaks.......

not bike related but if this helps..........I am rebuilding an old v6 engine at the moment where the bolts attaching the exhaust manifolds to cylinder heads had been replaced with allen key bolts - I had 3 (out of 12) that rounded off including one where torx bit then broke. Plus 4th one where the bolt snapped. These were 5.5mm bolts.

One came free after heating with oxy-acetylene torch - probably not an option ?

The other 2 we cut the heads off so the manifold could be removed. This then took the tension off the bolts, one just then unscrewed by hand having been previously rock solid, one (which had snapped) had to heat and a mole wrench on the stud and a lot of back and forth freed it off, the final one we still had to drill out, and I am still in process of picking out remaining thread with a tap.....

if you are drilling out then would use a left hand thread drill bit with drill in "reverse" so drilling action is unscrewing bolt rather than tightening it up further

 

[voodoorider]

Thanks.. Yep just spoke with my Dad, he taught mechanics for like 30 years after RAE and cranfield institute... So what he doesn't know....

He agreed with the drill/heat/mole grips.... I wonder where I can source some left handed drill bits in Dallas.... Off to google I go.

 

[marc two tone]

Worst case scenario....

How essential is it that the two triangles are separated?

I think, going by the pic that there are two colours.? Some powder coaters can/will find a way to mask or shield one colour application from another.

This may save you some stress and that 'oh crumbs#' the bolt has sheered, now it's a drill/tap situation.

#add expletives as necessary.

 

[cherrybomb]

Alternative option to a LH drill bit (which will be tough to find at best) is to drill the head off so the parts can be separated.

This should allow you access to put the part with the remains of the bolt onto a vice so you can use a pillar drill to drill a hole down in to the centre of the bolt shaft.

Then use a little jobbie called an 'easy out' They look like a cross between a screw and drill tap. These have a LH cutting thread and the idea is that you screw them down into the hole in the remains of the bolt and as they grip they'll wind the bolt out.

Careful how you use them though because if it breaks off in the bolt there's not a drill bit readily available that will touch it as its hardened cutting steel.

 

[racer x]

Could try and spot weld tacking a Allen key to the bolt if possible that would work only if you can get in to weld the bolt key to the bolt head