Drill guide Tool for removing top suspension bolt

[rhencullen1989]

Hi there,

As it looks like I will be replacing all of my control arms in the near future, I am obviously dreading the removal of this stubborn bolt that holds the upper arms to the hub carrier (upright). I have successfully done the B5 ones before, but the upright leg on the B5 is made from steel and the bolts came out without too much fuss.

Now these B6 legs of the finest aluminium seem to be a bit of a mare to say the least (corrosion between two dissimilar metals)

The best solution would seem to be to drill these pesky little blighters out, but what if the drill wanders, you will mess up your upright, right!

I am looking at machining up some drill guides, these will be approx 80mm long stainless steel (allowing approx 30mm for tapped M10 hole, means a drill guide of approx 50mm). One end will have a 10mm thread to screw onto the bolt thread once the nut is removed (guessing at about 30mm or so in length) they will be approx 25mm diameter, the depth of thread will be the same as the length of thread stuck out from the upright. they will have a through hole of 5mm diameter and 8mm diameter ( I am going to make 2).

The idea is to screw the 5mm diameter one on first and drill as far as possible with a 5mm drill, remove that drill guide and screw on the 8mm guide and drill 8mm as deep as possible. Obviously as the tapping drill size for M10X1.5 is 8.5mm anything over 8mm would have to be done using the 8mm hole as the guide hole, so a 9.9mm drill could be used to clean out the remainder of the bolt.

I think this will work, the idea I had was to remove the whole assembly and do it in the garage, where you are not so restricted with room.

What do you think?? will it work well?

Let me know your thoughts.

By the way this will be for my use only and I have no interest to sell them.

Cheers, Rhencullen.

[Crasher]

There is a proper removal tool made by Klann but it is daft money and slips off and whacks you on the hand and it hurts! What we do is use an induction heater with an induction wire wrapped around the area. Don't use a naked flame though, the ally does not take kindly to it. We did this on a 3B Passat with the steel uprights yesterday and it worked far more easily than the extractor tool (a different one) which can break itself or bend the bolt. Drilling a 105mm long bolt straight is not my idea of fun.

[rhencullen1989]

We use Guhring drills at work on the CNC lathes and you don't even need to centre drill with them. I think as long as there is a drill guide that is the same size as the drill and screws onto the thread of the bolt nice and squarely it should work pretty well. When the time comes I will let you know how it goes. Probably not till next year now when the weather gets better again.

[VAG-Abound]

I'd be cautious of the ability of the 8mm guide to stay true after the bit of bolt it has been screwed into has been drilled out. Even for the smaller drills I'd be wondering if the tip was staying coaxial with the guided part.

After drilling with the smaller bits I'd see if a sharp twist with an impact driver would free the now more tubular rather than solid bolt.

Has anyone tried putting a high current source like spare battery with suitable resistance load on each end of the bolt to heat it up? Should have a similar effect to induction heater I'd have thought.

[rhencullen1989]

Mmm, heating the bolt up will expand it, which is the opposite of what you want. If heat is used to expand the aluminium leg, then great care needs to be taken. As Crasher has stated above, they certainly don’t like naked flames. A decent hot air gun can get to 300 odd degrees. I like the idea of drilling out most of the guts of the bolt and putting some torque behind it. A tube is stronger than a solid under torque. I just don’t like the idea of whacking the sh%@ out of it to get it out, if it does not move after half an hour of penetrating fluid and moderate heat, then I am going for the drilling option with my drill guides/bushes.

[VAG-Abound]

The steel bolt would expand, but so would the alloy by about twice as much. That should crack and separate (by a very small amount) the corrosion.

Putting a high current through it would somewhat risky unless some thought was put into it. I'd think some of the DIY spot welder timers could be repurposed to put enough energy in, with some form of failsafe MCB or fuse in the circuit to prevent runaway red hot bolt / boiling battery event.

My initial calc is that 12V through the bolt would give a ~20A current, and leaving it in place for 30 seconds or so land enough energy to would raise its temperature by 200C if there were no heat loss. That's off on a few points though. Some current and heat will head into the alloy, so current draw on battery would be higher and end temperature lower. A 24V / 40A / 10s blast might be better...

[Crasher]

Yes, the ally expands faster and more than the steel, the induction heater gets one moving in about five minutes and using the air gun the bolt can be spun and it comes out. These induction coil wires are getting expensive though, you can only use one about four times and it burns out and they are £20 each.