The old 'broken bolt' question

[jrt]

Hi Folks,
I broke an M6 bolt off in the shock mount of an EV.  My own fault, but I still curse bolts made from cheese or cheese-food-product.
Anyhow, I shocked it, drilled it out some, tried an ez out, tried a left hand drill bit, tried a different style of ez out but it won't budge.  There is not enough bolt left to weld anything to it and it is flush or recessed in the shock mount.   For such a soft bolt (stainless? maybe)I am surprised.  Maybe it galled into the mount?
So- drill it all the way to the back and use a tap?  I think it is about 1/2 drilled out now- roughly center but not exact.  I would be delighted to hear any other options. 
Thanks,
jrt

[fotoguzzi]

Heat cycles and penetrating oil?

[Dirk_S]

That’s what I had to do when one of my rear shock mount bolts got stuck. Drilled all the way through (wasn’t 100% center, but thankfully good enough). Kept drilling through with bigger bits until the remaining slivers of bolt came out. Then re-tapped the hole with a heli-coil.

[jrt]

Heat cycles and penetrating oil?

Tried one heat cycle but no penetrating oil.  The bolt and receiver (what is it called where a bolt goes into a receptacle?) was not rusty at all.  I just overtightened and it sheared.

[jrt]

That’s what I had to do when one of my rear shock mount bolts got stuck. Drilled all the way through (wasn’t 100% center, but thankfully good enough). Kept drilling through with bigger bits until the remaining slivers of bolt came out. Then re-tapped the hole with a heli-coil.

Yep, I'm very close to center so not that worried about losing material from the walls.  Good to hear that someone else has re-tapped the fitting.

[pehayes]

Make sure you use good quality LEFT HAND drill bits.  With heat, the bit might grab and spin out the residual of the bolt.

Patrick Hayes
Fremont CA

[jrt]

Make sure you use good quality LEFT HAND drill bits.  With heat, the bit might grab and spin out the residual of the bolt.

Patrick Hayes
Fremont CA

Thanks Pat-  I can try some heat on what is left (ha), but there ain't much.  I used a smaller, then a larger left-hand bit but now I am close to being out of material to grab.

[tris]

Drilling out works (twice now on step sons vehicle), but take your time and small steps checking regularly

if you're lucky it will just break through and with a pick and some needle nose pliers you will be able to grab the remainder of the bolt and wind it out like a helicoil

[Stevex]

If it is stainless steel and has galled, I doubt you'll get it moving.
I use a lot of stainless and have only ever had one nut gall on a bolt; it's like a cold weld.
I reckon you'll have to drill and tap.

[Chuck in Indiana]

*If* you have a wire welder, you can weld a nut on it..by far the best way. If not.. yep, keep going with progressively larger drills.

[jrt]

And it is out....mostly.  Enough to put in a helicoil anyway.

[Chuck in Indiana]

Attaboy. Perseverance wins the day..

[pehayes]

Is that the broken piece we see in the center of the pic?  Round?
Why do you need a helicoil?  Were original threads damaged?  Why not just run a tap in the original hole and clean up the threads and use as is?
Can you post a picture of the mount in question?
There was a terrible problem with 98EV and the mounting of side luggage racks.  The factory made an internally thread lug, drilled hole in the frame, mounted the lug over the hole and welded it up.  Unfortunately, lots of welding slag in the bottom of the threaded hole.  Put in a bolt and tear it up.  Had to run a tap in brand new bikes in order to properly mount luggage racks.

Patrick Hayes
Fremont CA

[jrt]

Ya, thanks Chuck.  Slow and steady.  Thanks for your advice.
Pat- the reason I had to use a helicoil is that when I drilled it out there were two issues- one is that the dang remainder of the bolt wouldn't let loose- I used a dental pick, but just couldn't get any of it to budge.  The second (and likely more important) reason is that the hole I drilled was just a tiny bit off center.  Oh- the third reason is that it was super-difficult to even get in far enough to put a helicoil in.  I don't know what happened, but that cheesy bolt turned into something super-hard.  OK, it probably work-hardened.  I broke a small carbide mill and two cheap drill bits. Eventually got deep enough with a 1/4" cobalt drill (starting smaller, then worked up) that I just tapped it with the helicoil thingy. 

[Dirk_S]

I’m not sure one would t want a heli-coil. It allows you to continue using the same size bolt, which means not having to worry about remembering that it’s a different bolt now. Plus, it’s an easy enough job once it’s tapped, and Heli-coils are shown to make for even stronger fastening than original.

Since I re-tapped the shock mount on mine, I haven’t needed to worry about it.I’m using extra long bolts in mine due to the modified pannier rack setup I’m rolling with.

[John A]

Good job! It just holds the shock on the post and if anyone ever even notices ( doubtful) that it’s not zackly on center, tell them it’s to counteract engine torque 

[jrt]

Good job! It just holds the shock on the post and if anyone ever even notices ( doubtful) that it’s not zackly on center, tell them it’s to counteract engine torque 

lol.  That's the spirit.

I used a center punch initially- just eyeballed it for the first drill bit.  Next time, I'll be even more careful and not assume it is going to come out easily.  I'll make a jig on the lathe to ensure my punch or drill is centered.  That's my lesson from this, in case anyone reads this thread at the appropriate time.