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Removing stuck grub screws from Steering Wheel


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I have an adjustable wheel on my TR3a which is currently fitted with a wooden Mota Lita steering wheel. Alec very kindly gave me an original wheel on the basis I swap mine out with him so I went to look at "whipping off the old wheel" today. It's never as simple as you think is it.................

 

First problem encountered about 2 minutes into the "refurb". The grub screws have welded themselves in the wheel and only one of them has the screw head left. The other two have been chewed up.

 

Any suggestions how best to get these out. I have heard of them being spark eroded out but this sounds a) expensive B) time consuming sending it away etc. Is there something I can try before I resort to professional help? I am keen not to knacker what turns out to be a difficult/impossible part to replace.

 

Thanks

 

Richard

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Richard - If its the same as my Moto-lita installation, the grub screws are there to hold the indicator switch in place. Until you have undone those you can't withdraw the indicator mechanism to get at the wheel mounting nut, is that right?.

 

Personally I would be very wary of using a blowtorch near cockpit trim materials and if you have retained the original indicator switch, heat may not do it any favours either.

 

I think I would try to drill out the grub screws. If you have the standard Moto-Lita aluminium wheel boss the worst that can happen is that you damage the boss but that is easily replaced. The problem is that the screws are high-tensile steel which is much harder than the aluminium they are threaded into. You need to take it carefully with a small drill first following the hole in the grub screw, then open it out with successively larger drills until the thread is just cut through. Try not to drill too deep as otherwise you may hit the switch mechanism which is difficult to replace. If I recall correctly the wall thickness of the boss is less than 10mm. The screws in mine are M4 so if you start off with a 2.5mm drill and work up to 4mm that should do the trick.

 

(Don't be tempted to try those useless cheap left-hand-thread 'screw extractors' as they are liable to just break off in the hole and ,being hardened, are all but impossible to remove if they do.)

 

Good luck.

 

Rob

Edited by RobH
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Hi guys,

 

Thanks for this, but just to confirm the stuck grub screws are in the original adjustable wheel rather than the Mota Lita boss. I need to remove the boss to fit the original wheel (and fortunately, all the grub screws came out of this fine as they are hex heads), but it seemed pointless to continue refurbishing the original wheel until I get the grub screws out.

 

However Rob, I think your suggestion to drill the screws out might be the only way out of this. Two of the grub screws have no discernable screw head left that I can see so getting hold of them with anything looks difficult (although that screw grab looks good stuff - wish I had some of that earlier today trying to get the ground out crossheads out of the garage wall).

 

If I drill them out, is it likely that you expose the threads and then you can pull what's left of the screws out leaving the threads undamaged? The last thing I want to do is wreck the threads

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Ok Richard - sorry I misunderstood.

 

If the screws are 10-32 as Peter says, the thread core diameter is 4.1mm, so a 4mm drill should just nip the base of the thread allowing for a bit of wobble. With luck the screw will be cut through without damaging the thread itself too much. The remains of the screw thread can then be picked out of the threaded hole, or better run a tap through to clean it up. BUT in reality you probably won't get the hole dead central with a hand-held drill.

 

It might not be too big a deal if the thread is slightly damaged as you can always have it re-tapped a slightly larger size.

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Before reaching for the drill given these are high tensile grub screws, is a product called "Reducteur H72" available over there ?

 

It's a new generation super release agent (bolt buster) that works in about 30 seconds. Good stuff for car restoration work.

 

Or try what's colloquially known in America as Weasel's P1ss (technical term !). Equal parts acetone and auto transmission fluid. Much better than WD40 or the like.

 

A 5mm screwdriver head from a hex set allows more turning force on the grub screws that an ordinary small screwdriver.

 

Viv

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Hi Richard,

| am surprised that you have anything other than slot head grub screws but no matter. My suggestion is that you clean the inside of the wheel where the grubscrews trap the indicator unit.

Make a plasticene cup for each hole and fill with the freeing agent of choice, diesel would be mine, just enough to cover the hole and thread, leave it overnight.

Even if the lugs for a slot head are broken off there's usually enough to get purchase and screw in as far as you can, if it will turn at all turn it backwards and forward a little more each time. screw it in not out, as that was the point it broke. Once you have some thread out use a fine wire brush, (find suede brush works) work the screw backwards and forward till you can get enough to cut a new slot.

Don't be tempted to start drilling anything at the moment till exhausted all possibilities

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Hi Richard,

 

sorry about this little saga - I hadn't tried dismantling the wheel I gave you . . . . .

 

I do have a small amount remaining of an old-fashioned red penetrating oil - the stuff that blows your head off if you're silly enough to sniff it, which is why it isn't available any more.

 

Derusto loosens most things, if necessary I can put some in the post to you, along with some phosphoric which will also help break initial corrosion.

 

Otherwise Gus will have something in the University engineering workshop that will get the blighters out.

 

Give me a bell or email .. . . .

 

Cheers

 

Alec

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The devil with drilling them out is that without lots of care it is easy for the drill to wander into the nice soft aluminium.

Is the tip of the screw visible in the boss where the horn push goes? Is there enough meat to grip with pliers or vise grips? Warm with blow lamp soak with suitable fluid, try to undo, just to get moving in hole using grips.

Could also try plumbers pipe freezing spray if heat is bothering. Thermal shock may free the little tinkers.

 

Cheers

Peter W

 

PS screw grab is terrific but beware of shearing the head off a seized fastener. I keep a bottle in my electric drill driver box.

Edited by BlueTR3A-5EKT
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Of course its sensible to try all other simple avenues before drilling. Its even possible to dissolve steel without harming the aluminium, using a saturated solution of ALUM - an old machine-shop trick used to remove broken taps. It might be difficult to do in this case as you need to immerse the parts in the solution and warm it up for a while.

 

Alan - you don't need a carbide drill for HT screws, ordinary HSS is quite sufficient. They are not hardened - just a bit tougher than mild steel that is all. In fact if Richards screws have (had?) a slot head they probably are not HT anyway.

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I've had very good luck with two of the products sold over here for loosening rusted fasteners. PB Blaster and/or Kroil. Both work well -- the former easily found and the latter maybe a slightly better product but a lot harder to find. And there's always the ATF/acetone mix noted by vivdownunder. Time is your friend here -- weeks of soak time can help on a tough nut in no hurry.

 

I'd give every chance for chemistry to work before attempting to drill the grub screws out.

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If you are going to attempt to drill out the old screw then it is important to start the drill exactly in the centre of the screw.

To help with this, find someone with a small lathe and use it to pre-drill a pilot hole in a new screw of the same thread as the old grub screw.

Insert the pre-drilled screw into your steering boss on top of the old grub screw and use the hole to guide the drill.

 

Bryan

NZ

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...The allan key replacements I use come in high tensile (or stainless) and have the taper on the bottom that secures the control head.Viv

Stainless steel Allen key replacements for those grub screws (or set screws in American) sounds like a super upgrade, Viv. This is one of those areas where authenticity makes no sense.

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leave em be,redrill and tap 3 new holes ,fill and refinish original holes.

If the control head has already been removed, this would be the option I would go for. I would clean off any protruding bits with a Dremel and fill with JB weld (or similar) and refinish with black enamel.

 

Rgds Ian

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Just to clarify, Richard has an alloy wheel and boss, with control head, currently fitted to his car - it has the adjustable steering column.

 

I gave him an original adjustable wheel, complete with grub screws but without control head.

 

It's the grub screws in the adjustable wheel that are the problem, and the wheel is not on the car !

 

Cheers

 

Alec

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leave em be,redrill and tap 3 new holes ,fill and refinish original holes.

You can't do that, the original threaded holes are in a special place with more meat in the wheel hub, any other place and they don't have enough ally to go through

Edited by TR24178
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