Broken crank bolt

[JGuy07]

I'm actually thinking of trying to find a carbide bit and just removing everything with the bit and then re-threading. Ram is right it would be easier and I would've been done by now if I just did that from the start. Only question now, what actual bit do I use to redrill/widen the hole when the bolt is finally removed? A reamer or just a normal like carbide bit?

[guppymech]

Trying to save the threads is preferable to me but if that is not possible you could heli-coil the hole. There are Tap and Drill charts that specify what size drill and taps to use for each size of bolt. You need to understand bolt thread nomenclature, ex: minor and major thread diameter. Search the web for information to learn these things so you don't ruin your crankshaft.

[JGuy07]

Threads can't be saved, my awesome noob like status with the drill caught them a few times. So, what size drill bit would I need in order to drill the new hole in order to use an insert to bring it back to the normal 7/16?

I have drilled out all but maybe 1/16 of the bolt and its thread locked and seated so it won't budge. I'll drill a completely new hole like ram mentioned. So what size drill bit do I need now? If I enlarge the hole I would also have to redrill the center hole in the hub wouldn't I? (This being without the insert and just rethreading to use bigger bolt)

If insert is used, I am completely lost at exactly what to get. Been reading on helicoils, timesert, threaded inserts etc and they all have pros and cons that come with precise drilling size and installation. I found a price for timeserts and the kit would be over $100 or so for the simplest kit I found online. Kit contains drill bit, counter bore, tap, install tool and inserts. That price is still out of my range for now after buying all the bits earlier used for drilling. I know what I need to do, and then I know what I CAN do or have funds for and they are different. Whats the best route now guys?

[JGuy07]

What about this, not sure about the brand though...? "Helical"? Something like this would be what I need?
http://www.grainger.com/Grainger/Hel...pair-Kit-5WE94

Was told to use a drill bit that is 1/64 larger then the size I actually want when using inserts. So, I want a 7/16-20 then my drill bit or new hole size would be 29/64, is that how it is done or is that wrong? Drill the new hole, rethread the hole with same thread count desired (20) and then install the insert. I haven't read up on the process yet that's just what I was told.

*****Had longer post with details prior to this but not showing up until 'approval'

[z28cam70]

that kit looks like a generic helicoil. time serts are much stronger than helicoils. most gm dealerships use timeserts as it is the method that GM uses to repair damaged threads. i have used timeserts in numerous applications including repairing stripped rocker arm studs with great results. save your money and do the job right the first time it will save you time and money in the end. the only other way i would repair this would be is to rethread the hole for a bigger bolt but it is easy to break a tap off in the hole and then you would be in a worse situation than you originally started.

[JGuy07]

Yea, rethreading a completely new hole for a bigger bolt was on my mind too. It would also ease the mind knowing the new bolt has a firm hold throughout the entire threads rather then just a small section of where the insert is. But, I would also have to drill the hub center hole larger. I have a tap set already, would just need the larger drill size and make sure I have enough cutting fluid.

(Finally found them) Oreilly sells the helicoil kits which have the inserts, tap, and install tool for under $30 though. People have good luck with helicoils as well. Would just need to make sure the hole is straight and be careful with drilling again. I think I got some good practice while drilling out the bolt o.0

[Chris]

Reading through this, sounds like a perfect reason for a stroker crank

[JGuy07]

If this wasn't my DD now and I had time and the cash...oh the possibilities that have crossed my mind

Inserts are out, new bolt size is in. Jumping up to a 1/2" and grabbed a 1/2" cobalt & tungsten bit with carbide tip. Will drill out the snout to hold the new 1/2" bolt. Will also use a drill press to help with drilling the hub. Grabbed plenty more cutting and rethreading fluid as well as a bulkier t-wrench for the tap. I've been working with the rad and condenser still in so I'm probably going to have to take those out in order to get enough room with this larger bit and the drill I have. Hope this goes well. Any other advice to give for enlargening the hole and rethreading?

[guppymech]

You better STOP and read how to drill and tap holes. You do not use a .500 size drill to make a hole for a 1/2 size bolt. Look at the link for the tap and drill chart below.

http://buydrillsuk.co.uk/wp-content/...rill-Sizes.jpg

[JGuy07]

Was under the impression the imprints on the taps indicated what size drill bit required. My 1/2 tap in the set I have has a separate set of stamped numbers reading 1/2" so I figured that was the drill size. I know there are different taps which require different things, but just made an assumption and guess I was wrong. So would I use the 29/64 bit to drill the new hole in order to use the 1/2" bolt? Can't seem to find that size anywhere around here since that was the size I was looking for when considering the inserts.

The tap I have is 1/2-20, and I guess I'll have to search more for the new bit.