Sheared Hub Bolt - Drive Flange to Hub Bolt

[tweetyduck]

One of my rear hub bolts is sheared off. ( i didn't do it ) Its now time to change/fix it.

The drive flange is back on and this obviously reveals a lovely guide hole (the one in the flange) in exactly the correct place for the hub bolt.

Should i just get a 10mm drill and use the drive flange hole as a guide and drill the hole as 10mm? Or am i going mad? What size hole do you drill before you tap M10? This will let me know what size drill to use. Should i use a smaller drill or just use the flange as a guide and go for it?

Advice Welcomed.

[Les Henson]

If you drill out 10mm, then you would have to fit a bigger bolt, as you won't be accounting for the thread depth, so 12mm would be the next size up. I think the thread depth is 1.25mm, so you would have to drill out with a 8.75mm drill, remove the remains of the thread, then the original bolt can be used. Not sure about this so, hopefully someone will say for definite. The usual way I do it is to drill from small - getting bigger until the remains of the thread can be removed. It takes a lot of accuracy to drill dead centre and get the old thread out without damaging the hub thread.

Les.

[tweetyduck]

Thanks Les, i was googling and had settled on 8.5mm which according to (some) tables is the drill size for M10 before tapping.

As for the accuracy i know what you mean. It needs to be bang on .

I'm wondering if the flange is the key here, as surely thats lined up prefectly as the other bolts are all tightened up. Its either this way or to try a guide hole and a remover tool. Someone else might have some previous experience and i'm in no rush to try this madness

[Simon119]

Could you use a 10mm drill bit through the drive flange just to start the hole you need to drill (just the very tip of the drill needs to make a hole). This would show you where the centre of the bolt is. then you can drill up to 8.5mm before tapping.

Hope this makes sense.

Simon

[TSD]

Thanks Les, i was googling and had settled on 8.5mm which according to (some) tables is the drill size for M10 before tapping.

As for the accuracy i know what you mean. It needs to be bang on .

I'm wondering if the flange is the key here, as surely thats lined up prefectly as the other bolts are all tightened up. Its either this way or to try a guide hole and a remover tool. Someone else might have some previous experience and i'm in no rush to try this madness

Left handed drill bits are ideal for this job (with a reversible drill of course!). Chances are, it won't matter if you arent perfectly in the centre because as you move up to larger drill sizes, the stud will usually unscrew itself.

[tweetyduck]

Thanks guys. I'll give it a try with a large one and then start smaller as Simon said

If i had some lefty handed i'd try that but not got any. I'll try machine mart.

Thanks,,,will let you know how it goes.

[crwoody]

The last time I had to do this (on a Disco 1) I used a smaller drill, about 5.5mm I think, and a stud extractor.

To keep the drill centred, I used the same drill bit to drill through the centre of the head of an M6 cap head (allen) bolt, until the head separated from the bolt, this left a nice centring guide which is a decent fit in the hole in the flange.

[Aragorn]

Be careful with stud extractors. More often than not they will shear off, leaving an impenetrable plug in your hole.

I have a spare hub with the same problem, but i've never made any efforts to remove it.

[tweetyduck]

done...drilled 10mm using the flange as a guide to countersink the head of the bolt. Then 4mm using the countersink mark to get it central. It wasn't central but the MachineMart special "Clarke CHT123 Screw Extractor & Wrench Set" did the trick.

Super. Thanks for all the help everyone.