Drilling out a sheared bolt

Padowan

Padowan

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In a now regretful and ham-fisted moment, while trying to remove the front ABS sensor and clean it to eliminate possible causes of spurious ABS errors, I managed to shear off one of the mounting bolts.

The sensor is still held firmly in place with the other bolt, but for piece of mind I want to eventually remove the bolt and fit another.

Any tips on drilling out and extracting a sheared, smaller bolt (think it's an M5), considering how delicate the cast webbing that it attaches to on the leg, I'm reluctant to even centre-punch it too hard, for fear of bending/shearing the web.

Please tell me I don't have to to take the leg off, and drill it out using a drill-press in order to be accurate and true-enough - in which case I might just leave it alone! An in-situ repair would be much appreciated!
 
If you have someone hold a hammer or some other heavy item behind the casting then that will support the casting and absorb the shock. You will be able to centre punch it.
You say you have 2 bolts holding it on. You could find out what size the clearance hole is on the sensor itself remount it with the single bolt and use that as a guide to dimple the end of the bolt. Take off the sensor, then use the tapping size to drill the bolt. Couldn't say without seeing it though.
Is the hole a blind hole or a through hole?
If it's a through hole and you are careful when drilling it, then as you drill it, it will tend to screw itself on through the casting and out the other side.
If it's a blind hole you could buy a left hand flute drill which tends to unscrew the thread as you drill into the bolt. Tapping size for M5 is 4.2mm. (Metric threads you take off the pitch from the dia to obtain tapping size) I would stay clear of stud extractors. I have had people bring in stuff to the workshop with broken extractors in the bolt which makes it even harder to get the dam things out.
I am assuming you have sheared off flush with the top of the casting and have nothing left of the bolt to grip?
You could try tapping gently with a fine centre punch to see if it rotates and possibly back it out that way.
If Loctite has been used heat the casting gingerly with a blowtorch and this softens and/or melts the Loctite. Keep an eye on where the flame is pointing and don't burn yourself nor the bike wiring etc.
It also would be useful to heat the casting gently anyway, as this may ease the thread. Aluminim expands quicker than the steel and may break any slight bond there is twixt bolt and casting.
You need to take it slowly with the revs on the drill too and try to keep the drill square when drilling. A mate sighting the line the drill is taking is useful so that it doesn't wander into the Aluminium, which it will inevitably want to.
Failing all that, if it does transpire that the drill wanders into the Aluminium and buggers up the thread, it can be drilled out to 5mm and then a Helicoil inserted. Helicoiling requires a special oversize tap and a stainless wire insert putting in and is a workshop job, but should be doable on the bike.
 
Nobbyspiles said:
If you have someone hold a hammer or some other heavy item behind the casting then that will support the casting and absorb the shock. You will be able to centre punch it.
You say you have 2 bolts holding it on. You could find out what size the clearance hole is on the sensor itself remount it with the single bolt and use that as a guide to dimple the end of the bolt. Take off the sensor, then use the tapping size to drill the bolt. Couldn't say without seeing it though.
Is the hole a blind hole or a through hole?
If it's a through hole and you are careful when drilling it, then as you drill it, it will tend to screw itself on through the casting and out the other side.
If it's a blind hole you could buy a left hand flute drill which tends to unscrew the thread as you drill into the bolt. Tapping size for M5 is 4.2mm. (Metric threads you take off the pitch from the dia to obtain tapping size) I would stay clear of stud extractors. I have had people bring in stuff to the workshop with broken extractors in the bolt which makes it even harder to get the dam things out.
I am assuming you have sheared off flush with the top of the casting and have nothing left of the bolt to grip?
You could try tapping gently with a fine centre punch to see if it rotates and possibly back it out that way.
If Loctite has been used heat the casting gingerly with a blowtorch and this softens and/or melts the Loctite. Keep an eye on where the flame is pointing and don't burn yourself nor the bike wiring etc.
It also would be useful to heat the casting gently anyway, as this may ease the thread. Aluminim expands quicker than the steel and may break any slight bond there is twixt bolt and casting.
You need to take it slowly with the revs on the drill too and try to keep the drill square when drilling. A mate sighting the line the drill is taking is useful so that it doesn't wander into the Aluminium, which it will inevitably want to.
Failing all that, if it does transpire that the drill wanders into the Aluminium and buggers up the thread, it can be drilled out to 5mm and then a Helicoil inserted. Helicoiling requires a special oversize tap and a stainless wire insert putting in and is a workshop job, but should be doable on the bike.
Click to expand...

This guy knows his stuff:thumb
 
was given a little tip.
If you grind the tip of your punch on 4 sides to i little pyramid the drill picks up centrally on the hole easier.
I tried it , it works:thumb2
 
abrasion said:
was given a little tip.
If you grind the tip of your punch on 4 sides to i little pyramid the drill picks up centrally on the hole easier.
I tried it , it works:thumb2
Click to expand...

Cheers for that one mate, I will file away for future use. Never heard of that one in me puff....:D
 
I was helping a friend a who broke his collar bone falling off a ladder. The bike has been parked up for a month and it would not start and is parked in a public garage with no charger. When we removed the battery one of the battery terminal bolts sheered off. Waiting to see if the battery will take a charge but assume its the same course of action drilling out with a dremel or is there an easier way? Many thanks.
 
Nobbyspiles said:
If you have someone hold a hammer or some other heavy item behind the casting then that will support the casting and absorb the shock. You will be able to centre punch it.
You say you have 2 bolts holding it on. You could find out what size the clearance hole is on the sensor itself remount it with the single bolt and use that as a guide to dimple the end of the bolt. Take off the sensor, then use the tapping size to drill the bolt. Couldn't say without seeing it though.
Is the hole a blind hole or a through hole?
If it's a through hole and you are careful when drilling it, then as you drill it, it will tend to screw itself on through the casting and out the other side.
If it's a blind hole you could buy a left hand flute drill which tends to unscrew the thread as you drill into the bolt. Tapping size for M5 is 4.2mm. (Metric threads you take off the pitch from the dia to obtain tapping size) I would stay clear of stud extractors. I have had people bring in stuff to the workshop with broken extractors in the bolt which makes it even harder to get the dam things out.
I am assuming you have sheared off flush with the top of the casting and have nothing left of the bolt to grip?
You could try tapping gently with a fine centre punch to see if it rotates and possibly back it out that way.
If Loctite has been used heat the casting gingerly with a blowtorch and this softens and/or melts the Loctite. Keep an eye on where the flame is pointing and don't burn yourself nor the bike wiring etc.
It also would be useful to heat the casting gently anyway, as this may ease the thread. Aluminim expands quicker than the steel and may break any slight bond there is twixt bolt and casting.
You need to take it slowly with the revs on the drill too and try to keep the drill square when drilling. A mate sighting the line the drill is taking is useful so that it doesn't wander into the Aluminium, which it will inevitably want to.
Failing all that, if it does transpire that the drill wanders into the Aluminium and buggers up the thread, it can be drilled out to 5mm and then a Helicoil inserted. Helicoiling requires a special oversize tap and a stainless wire insert putting in and is a workshop job, but should be doable on the bike.
Click to expand...

very useful:thumb
 
You could try these... http://www.quikcenter.com/

They can take forever to get from the US though. I brought a set back in my hand luggage last time I was in the US. That caused some consternation with airport secturity in Indianapolis airport.....:augie
 
Some great advise there, plenty for me to have a go with. Thanks everyone, I'll let you know how I get on (hopefully not with a wanted:LH fork leg post!)
 
Schtum said:
You could try these... http://www.quikcenter.com/

They can take forever to get from the US though. I brought a set back in my hand luggage last time I was in the US. That caused some consternation with airport secturity in Indianapolis airport.....:augie
Click to expand...

Looks interesting but I guess in order for the tool to work part of the bolt still needs to be visible. In my case the bolt has sheared off flush with the battery casing.
 
No, you can configure it to go against a face where the bolt has broken off flush.
The idea is then that it is stuck with some superglue that'll hold the tool till you get the centre drill in.
All good in theory (see it on YouTube) but often there's not enough space to fit the thing.
Cue Dremel...
 
NorthLondonCookie said:
I was helping a friend a who broke his collar bone falling off a ladder. The bike has been parked up for a month and it would not start and is parked in a public garage with no charger. When we removed the battery one of the battery terminal bolts sheared off. Waiting to see if the battery will take a charge but assume its the same course of action drilling out with a dremel or is there an easier way? Many thanks.
Click to expand...

Yep this would be the same technique as described previously and should be a lot easier cos you will be able to remove the battery and clamp it gently in a drill press in a vice. The terminals will be Lead which is very soft so usually are not threaded. If you look carefully there should be a captive nut in the terminal so you should not have to worry as much about it being off centre. After checking that things are as I say, (never assume anything........) you should be able to use a 6 or 6.2mm drill and as soon as you drill deep enough then just poke out the nut with the sheared bolt in it and replace the nut. Off the top of my head, I think that the battery terminals will be 6mm thread. Usually its an M10 spanner takes them off.
 
+1 for left hand drill bit , if it doesn't unscrew it then you have already started the next step,

Don't go with the stud extractors/easyouts etc.

Oh, and be very carefull, if you snap a drill bit or tap off, it's a trp to get it spark eroded

good luck
 
Before you pick up the drill, is there any of the stud protruding from the casting? A stud extractor that grips the outside of the stud would be a better bet. And if it's only M5 a good pair of Molegrips should suffice. Plenty of heat will help as the alloy of the casting and the steel of the stud will expand and contract at different rates.
 
Nobbyspiles said:
Yep this would be the same technique as described previously and should be a lot easier cos you will be able to remove the battery and clamp it gently in a drill press in a vice. The terminals will be Lead which is very soft so usually are not threaded. If you look carefully there should be a captive nut in the terminal so you should not have to worry as much about it being off centre. After checking that things are as I say, (never assume anything........) you should be able to use a 6 or 6.2mm drill and as soon as you drill deep enough then just poke out the nut with the sheared bolt in it and replace the nut. Off the top of my head, I think that the battery terminals will be 6mm thread. Usually its an M10 spanner takes them off.
Click to expand...

Cheers M8. We'll first see if the battery takes a charge but didn't realise the terminals were lead so should be easy.
 
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