Help! Rounded off Allen bolt stuck!
- Thread starter wookiee
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visual speaks a thousand words :?
Re: Re:
look at the bolt you see the on the left around the 7/ 8 oclock postion atlot of the head is exposed use a very small chisel to make a indent / groove in the edge of the bolt a 6mm wood chisel would be ideal
then use a center punch to punch the indent anticlock wise an keep sharping the punch with a grinder when the point goes dull
very important use a very small hammer an take your time
this will work but it takes time
wookiee":2pp95nfo said:
look at the bolt you see the on the left around the 7/ 8 oclock postion atlot of the head is exposed use a very small chisel to make a indent / groove in the edge of the bolt a 6mm wood chisel would be ideal
then use a center punch to punch the indent anticlock wise an keep sharping the punch with a grinder when the point goes dull
very important use a very small hammer an take your time
this will work but it takes time
weeman_mtb
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Just to confuse you further, a method that I've had a lot of success with, both at work and home is using a left handed or reverse drill bit. It basically works like a normal drill but in reverse so that when it bites it will undo the broken/rounded bolt. Best case scenario ; it screws the bolt out, worst case scenario ; you drill a hole and move onto the the stud extractor.
This video explains it best https://www.youtube.com/watch?v=FYvaPbX1sT4
The good news is that you don't actually need a left handed drill bit, I've never owned one either. Just grind the clearance on a standard drill backwards so that it now cuts on the opposite faces ie. the angle "B" has to slope in the opposite direction. As with the left handed drill bit, the modded drill bit must also be run anticlockwise in the drill.
Just to confuse you further, a method that I've had a lot of success with, both at work and home is using a left handed or reverse drill bit. It basically works like a normal drill but in reverse so that when it bites it will undo the broken/rounded bolt. Best case scenario ; it screws the bolt out, worst case scenario ; you drill a hole and move onto the the stud extractor.
This video explains it best https://www.youtube.com/watch?v=FYvaPbX1sT4
The good news is that you don't actually need a left handed drill bit, I've never owned one either. Just grind the clearance on a standard drill backwards so that it now cuts on the opposite faces ie. the angle "B" has to slope in the opposite direction. As with the left handed drill bit, the modded drill bit must also be run anticlockwise in the drill.
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If you plan to do this yourself then do up the other bolt before drilling it - that releases some of the yension on the one you want out,
What is the bolt made of? Looks like stainless steel which will make it harder.
Is the gap wide enough for a junior hacksaw blade? If yes, then try to saw the bolt ( obviously without the other one fitted). There may be a bkt of plastic in the gap, this has a pin to prevent the arm from dropping off, sacrifice thay if nevrssary, it is not needed.
If you can get the crank arm off, this will increase massively your chances of removing it as you can clamp the arm down and use a drill press. A pilot hole of 2 mm icreased to 4.0 mm or whatever is the tapping drill size for m5. Dont usr 5 mm as that will drill into the crank threads!! This will leave the bolt threads that can be picked out either by hand or using a m5 tap.
If you were planning to use a hand held drill, the chances are you will snap the drill in the bolt making it even harder so dont.
Forget screw extractors too.
You could try using a dremel with small diamond tips to make a slot in the head, itll take time but try that before drilling.
What is the bolt made of? Looks like stainless steel which will make it harder.
Is the gap wide enough for a junior hacksaw blade? If yes, then try to saw the bolt ( obviously without the other one fitted). There may be a bkt of plastic in the gap, this has a pin to prevent the arm from dropping off, sacrifice thay if nevrssary, it is not needed.
If you can get the crank arm off, this will increase massively your chances of removing it as you can clamp the arm down and use a drill press. A pilot hole of 2 mm icreased to 4.0 mm or whatever is the tapping drill size for m5. Dont usr 5 mm as that will drill into the crank threads!! This will leave the bolt threads that can be picked out either by hand or using a m5 tap.
If you were planning to use a hand held drill, the chances are you will snap the drill in the bolt making it even harder so dont.
Forget screw extractors too.
You could try using a dremel with small diamond tips to make a slot in the head, itll take time but try that before drilling.
Re diamond dremel bits, see 271607090538 on ebay.
And if you do manage to get a slot, support the underside and use an impact screw driver to undo. That is less likely to slip.
If you were heading my way or were able to get the crank arm off to post to me, id have a go as i got a drill press. Not saying id succeed but more likely than someone without a drill press.
Ps take your time over this as it is easy to make the matter worse. :facepalm:
And you can buy replacement crank arms..
Onr more thing, the plastic preload adjuster is expendable but if you do cut into that, it should still be usable,
And if you do manage to get a slot, support the underside and use an impact screw driver to undo. That is less likely to slip.
If you were heading my way or were able to get the crank arm off to post to me, id have a go as i got a drill press. Not saying id succeed but more likely than someone without a drill press.
Ps take your time over this as it is easy to make the matter worse. :facepalm:
And you can buy replacement crank arms..
Onr more thing, the plastic preload adjuster is expendable but if you do cut into that, it should still be usable,
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