W123 Sheared Off Lower Sock Bolt Head Drill Out - PeachParts Mercedes-Benz Forum

Diesel911 · #1 04-14-2014, 05:00 PM

Change out a rear Shock Absorber on a W123 and I sheared/broke one of the Bolt Heads off.
I decided to try to drill it out with the Trailing Arm still on the Car.

I center punched what was left of the Bolt OK but I have always had trouble drilling a staright hole even when what I am drilling is on a Bench and I continued My tradition and got the Hole off center and likely at some Angle.

I only had 2 choices of Easy Outs (see pic) that I already have and as the M10x1.5 Bolt is not much larger in diameter than an 3/8" Bolt the Easy Outs in that size are not very sturdy.

So I one of the Easy Outs and it did not work and I stopped before I broke it.
I drilled the hole out larger and tried the larger Easy Out and it jus sort of reamed out the metal.

I tried drilling a hole on the outside of the Threads to see if that would relieve it a bit and tried the larger Easy Out but no luck.

Diesel911 · #2 04-14-2014, 05:10 PM

Since neither Easy Out worked My next plan was to drill out the hole using the Tap Drill (8.5mm) and Tap M10x1.5 I had bought at PepBoys for another Job that I never did.

Well the Drill was too soft and did not get Far.
I decided to use other Drill Bits that I had to gradually enlarge the Hole.

I did that until there was a sleeve threaded Meatal left inside the Hole.

The threaded Metal Sleeve was pried out and I chased the threads of the Hole with the Tap.

The problem now is that due to my crooked drilling there is only about 50% if the threads left.
That leaves Me with the choice of using it as it is and see how long it will last or installing a Helicoil or drilling it oversized and using an oversized Bolt.

I am going to try to go with the oversized Bolt because that is cheaper than a Helicoil and I already have a Tap and Tap Drill for that. 7/16" is the closest US size that is just a bit larger than the M10 Bolt is.

First I need to see if the Local Industrial Hardware Store has the 7/16" in a suitable Grade first.
So until My Wife gets Home I have no way to get to the Store.

If that does not work all that is left is to get a Bolt long enough to go though that hole and allow acseparate Nut to be put on it.

Stretch · #3 04-14-2014, 05:11 PM

Drilling a straight hole under the car like that is difficult.

If you can get the hole to be the same size as the bolt needed to attach the shock (what is it M10?) you can use a longer bolt and a stiff nut on the other side of the nadgered threaded portion of the trailing arm. It is tricky to do this but I have managed to hold a nut in place with bent needle nose pliers stuffed through the coils of the spring.

The best option however is to remove the trailing arm and grind off the square threaded block and weld on a new piece.

Stretch · #4 04-14-2014, 05:12 PM

Ahhh we're posting at the same time - if you can't drill a straight hole you'll have trouble with helicoils.

Diesel911 · #5 04-14-2014, 05:31 PM

Quote:

Originally Posted by Stretch

Ahhh we're posting at the same time - if you can't drill a straight hole you'll have trouble with helicoils.

It will be the same issue with me drilling out for 7/16" although I suppose I could get lucky and the last Hole could be straighter.

For this particular purpose since the Bolt (one of 2 Blolts) only holds the Shock absorber in place even if the Hole is cocked/not straight as long as it has all a full set of threads it is better off than with 50% of the original Threads.

Diesel911 · #6 04-14-2014, 05:39 PM

Quote:

Originally Posted by Stretch

Drilling a straight hole under the car like that is difficult.

If you can get the hole to be the same size as the bolt needed to attach the shock (what is it M10?) you can use a longer bolt and a stiff nut on the other side of the nadgered threaded portion of the trailing arm. It is tricky to do this but I have managed to hold a nut in place with bent needle nose pliers stuffed through the coils of the spring.

The best option however is to remove the trailing arm and grind off the square threaded block and weld on a new piece.

M10 = 10mm

Even though I have another Trailing Arm (buried I My Grage somwhere) I did not want to remove the Arm unless I have to.

Diesel911 · #7 04-14-2014, 08:08 PM

So the Hardware Store had the 7/16" Bolts and I did the drill and tapping and it turned out fine.
I am not going to install the Shock absorber till tomarrow.

Stretch · #8 04-15-2014, 01:46 AM

Ahhh you now have a metr-inch Mercedes!

dude99 · #9 04-15-2014, 02:31 AM

When I did the rears on my 79 I had the same problem, snapped one bottom bolt on each side. Laying underneath the car made it near imposable for me to drill a nice straight hole (dull drill bits didn't help either), so I ended up just drilling the bolt out and replacing it with a nut and bolt. I added some locktite to the threads to make sure it didn't come undone.