Drilling subframe Bolts

[Bowie69]

I get very mixed results with them, and in that video the stud was loose, not rusted in as in this case.

I would like to try a LH drill bit though, these are apparently quite successful.

[newsh]

If a bolt snaps because of over tightening an easyout may work. If a bolt has snapped because it's rusted in then it's very unlikely.

[S2central.net]

In my "career" I have snapped about 10 so called easy-outs ... And maybe succeeded twice with the crappy things
- They are not easy at all for such a rusted bolt.

[Nuvo]

Here's a quick summary of things as they stand. The subframe bolt was recessed in the longitudinal member so I had nothing to grab on too.

As per post #12 I was able drill the core of the bolt out with with a ¼" cobalt drill bit using an angle drill. Since I was able to remove the remaining three bolts easily with no evidence of corrosion I was confident I would be able remove it using a good quality screw extractor.

I echo your experiences and concerns with so-called "easy-outs" having had one snap on me and I vowed never to use them again. This time I was happy to use them. If I felt any turning resistance I would have resorted to drilling out the entire bolt core and used a tap to remove the bolt threads from the hole.

The snapped bolt screwed out with ease. It seems a bit odd that the high pressure and slow speed drilling didn't screw it inside the longitudinal member. Having seen this, I doubt using left-hand drill bits would have screwed it out on this occasion.

The challenge I had was finding a way to accurately guide the ½" drill bit into the hole to remove the damaged threads ready for tapping to fit a keensert.
Pasbogdan's suggestion of welding a nut to the chassis to act as a drilling and tapping guide would have been absolutely perfect had I had access to a welder at the time. I'll do this next time. Thank you Pasbogdan.


Here is a blurry picture of the machined drill and tap guide I was unable to fit flush to the chassis leg.


Here is a pic of the chassis leg bolt hole and captive nut in its present state. Sorry for the quality of the images.

I'm starting to wonder if there are enough threads remaining on the captive nut to use it in its current state. What do you think?

Does anyone have a picture of a captive nut and can they tell me its dimensions please?

[Kieron20V]

If it screwed out fine with the easy out, id give the threads a clean up with the right size tap and you should be good to go. You havent removed any threads have you?

[Nuvo]

No, I haven't removed any threads, but I think the first few were stripped when the bolt snapped.
Since the part of the car was raised ~20" above the floor it was difficult to throughly inspect the condition of the threads.

Because there is doubt, I should probably play it safe and fit the keensert when I next get the chance to work on it.
I'd like to know the thickness of the the captive nut as the keensert is 14mm deep.

[newsh]

Yes, if it unscrewed it should be fine. From memory that looks normal. Well done Easy-Out!

Have you tried a bolt in there with some copper grease on?

[Nuvo]

Hi Newsh, yes a subframe bolt engages the 1.5 pitch threads easily enough.

[caterpillar]

remember its only those 4 bolts holding together the front end, with engine, tranny, steering struts( ok strut does have a nut in the top).. and the older verson does have only 10mm bolts ( to 91 mod; then 12mm) and a short little nut in the frame.. so i will have those threads done wery vell...( i will change those nuts to 12mm; but thats not easy, from the side of the frame, not from the underside) and i will use the long nuts, those you have to extent the threaded bar together.. they are 3-5 nuts height in one peace) and in 12mm...

[newsh]

Right so no need to use a tap anyway..

Caterpillar is saying to cut a window in the side of the chassis rail and replace the nut with a stud joiner nut, that would certainly be very strong!

http://www.ebay.co.uk/itm/BZP-Stud-C...item3f2594bbe8

[Nuvo]

Using a stud joiner nut is certainly a very good idea in principle, why Audi didn't use something like this in the first place I don't know, but as caterpillar says it would be a lot of extra work and expense.
I'll have a chat with a friendly mechanic I know and ask what he thinks.

[Kieron20V]

I see no problem with the captive nut. Good enough for a plane to fly at 45000ft, good enough for the road.

Only 4 bolts? Big deal, most jets I work on have the engines held in by 3 bolts.

The subframe bolts are only really taking a shear load, so no need for massive amounts of thread engagement.

[caterpillar]

subframe bolt and NUT issue

Right so no need to use a tap anyway..

Caterpillar is saying to cut a window in the side of the chassis rail and replace the nut with a stud joiner nut, that would certainly be very strong!

http://www.ebay.co.uk/itm/BZP-Stud-C...item3f2594bbe8

thats correckt... and if you weld this item in a solid peace of steel 60x 90x6 mm, and put tis in the fram; from the side, and fixure this with som weldin inside.. its MUTCH stronger the audis verson... then weld the sidesteel in the frame again... have some paint ... all are goodies... ( remember to fixer the subframe correct)... i will do this with my 32b quantum.... same ****, new wrappin