Snapped wheel bolt, tapping new thread

[sgking]

Hi i bought a car recently with a snapped wheel bolt. It came as a surprise but no big deal i thought. However im struggling as it was cross threaded and proper stuck in there!

Its a BMW so is a wheel bolt, which screws into the hub.

There was not enough bolt sitting proud to get the mole grips on, but i got some heat on it, tried chiseling it round etc etc but no joy.

I drilled it out with 8mm bit thinking the 'easy out' would then work its magic, but nope its stuck fast in there and not budging at all.

So my next port of call is to drill it all out and tap the hole to m14 x 1.25 which is the thread it was originally. Is the correct approach?

My questions as follows...

What size do I drill it? 13mm and then tap it?

If i do this, im guessing perfection is picking up the old thread and restoring it, removing the remains of the snapped bolt as i go? But what if my tapping creates a whole new thread... wont that be weak as its a mish mash of old thread and slivers of damaged snapped bolt, if you get what i mean?

Thanks

 

[Erie Fred]

Farm machinery uses wheel bolts, I loath working with them.....such a PIA trying to hold a wheel up
and getting the first bolt in.

You'll need to drill out everything, and tap larger, and source a larger wheel bolt.

 

[Nederlands]

Are you sure it has treads there?

I only saw push in with some sort of teeth

M14-1.25 is 12.75 i would drill 12.7 with this tread

 

[BrokenBiker]

be quicker and easier to just change the hub?

 

[BrokenBiker]

Farm machinery uses wheel bolts, I loath working with them.....such a PIA trying to hold a wheel up
and getting the first bolt in.

You'll need to drill out everything, and tap larger, and source a larger wheel bolt.

and also have to find wheels that match the new bolts?

 

[Dozzer]

I know this is a random thing to suggest on a Welding forum, but maybe weld an old wheel nut on the remains of the bolt then slowly work it out?
Otherwise im with @BrokenBiker get a new wheel hub, if the thread is really FUBAR, then a new bolt will not hold that well.
and a lot of the German stuff uses stupidly small pitch stuff like M14 x 1. and some BMW, Audi etc use LH thread on one side on the bigger stuff.

 

[BrokenBiker]

I know this is a random thing to suggest on a Welding forum, but maybe weld an old wheel nut on the remains of the bolt then slowly work it out?

we dont do that here

 

[harveyp6]

I'd find a specialist BMW breaker and buy a used hub c/w bolts.

 

[Melvyn Best]

I know this is a random thing to suggest on a Welding forum, but maybe weld an old wheel nut on the remains of the bolt then slowly work it out?
Otherwise im with @BrokenBiker get a new wheel hub, if the thread is really FUBAR, then a new bolt will not hold that well.
and a lot of the German stuff uses stupidly small pitch stuff like M14 x 1. and some BMW, Audi etc use LH thread on one side on the bigger stuff.

What? You mean actually do a bit of welding? Whatever next? Seriously that would be my approach to get the old bolt out but if the threads are damaged it might be safer to replace the hub

 

[hotponyshoes]

Grind the existing stump flush with the hub.
You'll then be able to see if the existing hole is still roundish or completely mullered.

If it looks ok make a jig to locate the center (3d printer is ideal) and drill it out working upto a 12mm.
The outside edge should then be thin enough to punch in until you have a Vee then break both halves out with a pair of long nose pliers.
If you can get the old one out hit the hole lightly with a countersink, clean out with a tap and see what it looks like.

If you can't get the old one out intact I'd be a bit worried about just retapping it as you could potentially tap at 180⁰ to the old start and cut the existing thread in half and leave it 50% weaker.
Having said that, if it's got 4 other good volts and it torques up ok I'd happily drive it myself..

Otherwise drill the whole lot out to clean metal (16mm+) and fit a solid type thread insert.

 

[Pete.]

I'd grind it flat, make a drilling guide located on an adjacent bolt and drill it out starting with a 5 or 6mm drill and then following with something like a 12.5. Then take a M14 x 1.25 taper or second tap, drill the previous drilling guide out to 14mm and run the tap through. You might get lucky and save enough thread to it's specced torque or you might up with a loose wobbly mess that required a repair with a wire insert.

 

[droopsnoot]

Farm machinery uses wheel bolts, I loath working with them.....such a PIA trying to hold a wheel up
and getting the first bolt in.

You'll need to drill out everything, and tap larger, and source a larger wheel bolt.

My old Audi coupe had the same issue, compounded by the fact that the brake discs are only held in place by the wheel bolts so can rotate freely when the wheel is off and, crucially, while you're holding a wheel and tyre up, turning it to try to make the holes all line up to get the first bolt in. That's annoying on a 14" wheel and tyre, so must be much more so on something with bigger wheels.

On the ur-quattro, which had larger and heavier wheels, Audi supplied a long stud that screwed into one of the bolt holes. That had the effect of fixing the brake disc in place, and also providing a place to hang the wheel while getting the other bolts in. If the stuff you're working with has a limited range of thread sizes you could knock up a few of those.

 

[Craig-SM]

My old Audi coupe had the same issue, compounded by the fact that the brake discs are only held in place by the wheel bolts so can rotate freely when the wheel is off and, crucially, while you're holding a wheel and tyre up, turning it to try to make the holes all line up to get the first bolt in. That's annoying on a 14" wheel and tyre, so must be much more so on something with bigger wheels.

On the ur-quattro, which had larger and heavier wheels, Audi supplied a long stud that screwed into one of the bolt holes. That had the effect of fixing the brake disc in place, and also providing a place to hang the wheel while getting the other bolts in. If the stuff you're working with has a limited range of thread sizes you could knock up a few of those.

You can buy these which I've used on Citroen and now on BMW, still a pain when the hub rotates but a lot less frustrating

https://www.amazon.co.uk/Alignment-Positioning-Fitting-Removal-Universal/dp/B08F5JHJ7F/ref=asc_df_B08F5JHJ7F?mcid=329eb580ed9c344fa10dfcc4996b6c53&tag=googshopuk-21&linkCode=df0&hvadid=697277611174&hvpos=&hvnetw=g&hvrand=14560988222040690332&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9217899&hvtargid=pla-1655678782764&hvocijid=14560988222040690332-B08F5JHJ7F-&hvexpln=0&gad_source=1&th=1

 

[droopsnoot]

^ Yes, that's the kind of thing. I made one for the coupe, ready for when it goes back on the road, by sawing the head off an old wheel bolt and welding a bit of bar (probably an old bolt, cut down) onto the end of it. The TT has discs that are fixed in place, so they're not as difficult to swap a wheel on, though it might be handy to take the weight.

 

[Melvyn Best]

^ Yes, that's the kind of thing. I made one for the coupe, ready for when it goes back on the road, by sawing the head off an old wheel bolt and welding a bit of bar (probably an old bolt, cut down) onto the end of it. The TT has discs that are fixed in place, so they're not as difficult to swap a wheel on, though it might be handy to take the weight.

I made one using an old track rod that I use a lot . Mercedes often have one in the tool kit

 

[daedalusminos]

Sounds like you've already drilled to 8mm... Gradually work up drill sizes until you just break into the old thread. You'll probably see this first as blueing inside the hole adjacent to the area closest to the thread before actually breaking through - at this point increase in fractions of mm drill size. If you've drilled close to centre the remnants will come out like a spring....if not you need to get them out as @hotponyshoes states. If the threads are damaged, try helicoil or if too bad an E-Z LOK insert or similar.

 

[sgking]

Thanks for your replies, you are confirming my thoughts that a new hub (and bearing) might be needed. I just thought id have a go, but seems its a tough one and probably beyond my capabilities.

As i have nothing to loose i will have a shot driling it as hot pony and peter suggest. Its sorned so not in use.

It seems like a good opportunity to ask about drill bits, ive never had much luck with the usual drill bits, but recently bought dewalt cobalt bits and they are incredible. What brand / type drill bits do you guys use?

Thanks

 

[addjunkie]

Good quality sharp drill bits do make a huge difference, I tend to buy Dormer. But any half decent HSS drills will do what you want, the secrets is to drill at the right sort of speed for the drill size and lubricate/ cool the bit.

The “cobalt” is just the higher percentage of cobalt in the steel used to make the drill bit, makes them harder wearing in theory. But if you over heat them the still blunt quickly.

 

[droopsnoot]

I mainly use what started out as a Halford set, though the 4mm that I use to drill pilot holes has been replaced with something else. The thing that made the most difference for me (as someone with no training, formal or otherwise, or background in metalwork) was when I bought a drill bit and the packaging told me what speed to use it at. Once I realised that the larger the bit, the slower it needs to turn, my drill bits last longer.

ETA - clashed with the above post.

 

[8ob]

Thanks for your replies, you are confirming my thoughts that a new hub (and bearing) might be needed. I just thought id have a go, but seems its a tough one and probably beyond my capabilities.

As i have nothing to loose i will have a shot driling it as hot pony and peter suggest. Its sorned so not in use.

It seems like a good opportunity to ask about drill bits, ive never had much luck with the usual drill bits, but recently bought dewalt cobalt bits and they are incredible. What brand / type drill bits do you guys use?

Thanks

If it’s not going well remove the hub before you destroy it and take it somewhere that has spark eroding kit. It’s a sort of nothing job if you have the kit.

Bob