Stripped 6mm Allen bolt

[Philoprof]

I stripped the topmost of the 2 6mm Allen bolts that fasten the front of the AC compressor bracket to the engine of my 380sl, and as the attached picture shows, I tried sawing a slit in the head, and using a socket with a flat head screwdriver tip to get it out.

But that didn't work, and I don't have a welder. So I guess I’m going to have to drill it out, and tap a new hole.

However, as I’ve never done that, I was wondering if someone here could tell me how difficult it is, and what size drill bit, tap, and replacement bolt I should use, if I do decide to do it.

As you can see from the picture, I’ll have to go through a hole in the bracket to get to the bolt. So I’ll have to use a long drill bit and a tap extension to get to it. But I don’t see that as being a problem, as both seem to be readily accessible.

OTOH, I’m a little afraid of the tap stripping the aluminum, and having to use a helicoil or other insert to get a new bolt to hold.

So, I would greatly appreciate any advice from anybody who’s done this before.

Thanks in advance.

Bill

[97 SL320]

If possible, unbolt the rest of the bracket and rotate it counterclockwise to assist bolt removal.

If can get a straight shot at the bolt head, use a flat nose punch and hit the bolt head, this will compress the metal and relieve tension. ( if this is going into a hollow aluminum cover don't hit too hard, if it goes through the cover into the block, hitting won't hurt it.)

Drilling can turn into a big mess.

[Sugar Bear]

Sockets that are designed to grab the outer part of rounded bolt heads are available, this may be an option. They are fluted/twisted on the inside to grab the bolt while you turn it out. Some general tips be patient and persistent and wear eye protection when drilling, hammering, chiseling spraying penetrating oils etc. and/or grinding.

If you can afford the time, spray an industrial grade penetrating oil on the bolt, strike it with a center punch and walk away. Repeat this multiple times several hours apart.

Can you grind the head off of the bolt, remove the bracket and then grab the remaining stud with pliers?

If you have to drill, try to get reverse drill bits it may just turn it out. If not, be absolutely certain not to drill too deeply, measure and mark the bit with something so you know when to stop. Have someone watch as you drill so that you do not drill on angle.

Had success once with this type of situation by epoxying the hex bit into the bolt head and turned the bolt out the next day after the epoxy cured.

[DRACO A5OG]

Carefully use a good vise grip and break it loose then remove it.

[Philoprof]

I’m ‘static, guys! “ ‘Static!” I got up early this morning and hammered a ½" socket on to the bolt head. But that didn’t work. So I went over to Harbor Freight at 8 A.M., and got their bolt extractor set for $15.99 with a 20% off coupon.

As you can see in the photo, each socket has teeth going counter clockwise. So when you hammer them on to a bolt head, they bite in, and grip it when you turn the bolt counter clockwise.

The ½" socket fit snugly on the 6mm Allen Bolt head even though I had cut a slot into it and deformed it. However, in retrospect, that may have actually helped the socket grip the head.

In any case, I pounded the socket down on to the bolt head, heated the block around the bolt, and turned the socket with a long extension.
Voila! It loosened the bolt in a few seconds, and not very much torque. It’s the greatest feeling in the world. Maybe better than sex, even, because it eliminated the need to drill that sucker out, or have it towed back and forth to an Indy.

In fact, as you can see in the photos, the bolt is a two inch long, steel lag bolt. So, to get it out, I would have had to drill all the way down to the end, then tap in new threads.

Now I can go away for the weekend, and get drunk without having to worry about it.

Take care, and thanks again for the ideas !

Bill