Ideas wanted fo unseizing grub screws in aluminium

[Chris Green]

I have some (boat) windows that I'm refurbishing. They are secured to the boat superstructure with little aluminium wedges with grub screws through them. Absolutely ridiculaous steel (not even stainless) grub screws in aluminium but I have to deal with what's there.

I removed one window a few weeks ago by angle-grinding through some of the grub screws and simply knocking out other wedges with a hammer. For that window I drilled out all of the grub screws, cleaned up the holes with a tap and put new stainless steel grub screws in (still not ideal but I can see no obvious alternative).

So, I'm starting on the next window and wondering if there's a better approach than drilling and re-tapping all the holes. I can knock the wedges out OK and I'm wondering if there's some obvious sort of chemical bath that I can soak the wedge plus grub screw in so that I might be able to get the grub screws out. They're quite small, maybe

1" long by 1/2" square section (they're not actually square) so don't need a big 'bath'. I can get a vice onto the projecting end of the grub screw so I can apply a fair amount of force but I need some help before they'll move I think. The grub screws are M8.

Any bright ideas anyone? Or should I simply give up and drill them all?

[Tim Lamb]

In message [e-mail]>, Chris Green [e-mail] writes

Can you apply local heat to the screws? Not easy when fitted but bit of red hot bar might cause enough local expansion for WD40 etc. to penetrate when cool.

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[Clive Arthur]

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I've no idea if this would work, but desperate times...

Connect a car battery, one lead to the aluminium frame and the other lead to your screwdriver/allen key - probably limit the current via a headlight bulb in series at least to start (well, you wanted a bright idea). Wear goggles and keep a swear box handy.

[Fredxx]

I'm trying to picture "aluminium wedges with grub screws through them" and how that would hold windows.

I would expect the aluminium to corrode and swell to keep the grub-screw captive. I'm not sure if stainless would fare much better.

If you are successful in removing the grub scree in soft aluminium then I might continue with doing that. I don't think anything will dissolve the grub screw that won't make a mess of the aluminium.

If the wedges are out of sight then Aluminium oxide is dissolved with most alkalis and acids. People have mentioned citric acid but not something I have ever used.

Tim's idea of heat might work relying on the different expansion of steel and aluminium. Best use penetrating oil after or you'll add carbon to the mix of oxides.

[RJH]

FWIW, I faced something similar and drilling was the only way for most of the screws - so a couple of good quality cobalt bits of varying size.

A couple I multitooled flats to the head of the screw and that gave just enough purchase to shift them with a hammer/sacrificial chisel.

[N_Cook]

Find a reverse action hand drill and maybe some lefhand drill bits , rare as hens teeth, and their housing has to be marked LEFT HAND in very big letters. Failing that some ordinary drill bits and grind a reverse rake angle at the tips. Often just the reverse action itself will shift them without having to drill into the grubs

[The Natural Philosopher]

There are simpler ways

these are not things that are falling off the shelves for £20 in LIDL...

In your case reverse drills and a reverse thread stud extractor, or drill the whole lot out and re tap is probably best cost-benefit approach.

Mild steel screws in aluminium threads are a disaster waiting to happen in a marine environment.

If these wedges can come out and onto the bench, then it will be easier to totally refurbish the whole shebang properly.

Or you can make new ones. I am not clear (picture would help) onm exactly how this all hangs together

[The Natural Philosopher]

Common as muck on Amazon Ebay etc. He is not the first person with this exact problem

The hardest part is drilling centrally - clamping on a pillar drill is top way.

[alan_m]

Impact driver?

Alternatively

First gently tap it in using a hammer at the end of the tool you use to undo the screw

[alan_m]

If it's not required to torque down the grub screws perhaps a good coating with grease (or an anti-seize compound) in the threads would prevent further seizure.

[The Natural Philosopher]

Even torqued down something that seals the gap against moisture but without gluing it all together would be excellent. That is what anti seize is, of course...

[Chris Green]

It would be easy enough to heat the lump of aluminium (with the grub screw in it) as I have removed them from the window/boat. I guess that might help a bit.

[Chris Green]

This is essentially what I did with the first few, I was just looking for a better/easier way! :-)

Absolutely! I fail to understand why a 'professional' business making windows for boats would do such a thing, but there you are. They've been in business since at least 1976 (when my boat was built)!

As I said, using brute force (a hammer) I can get them out without serious damage to anything, just a few minor deformations of the aluminium.

Here's a picture, end on, of a clean, new one:-

...and this is a rather poor picture of them in my boat:-

I think you can probably make out how they work.

[Chris Green]

It is rather an odd set-up, but amazingly I found the company that makes them is still in business.

As regards seeing how they work see the pictures I've posted:-

I think in reality with steel and aluminium together it's the steel that corrodes.

[Chris Green]

They have to be fairly tight to hold the window in tight enough to squish the seals to waterproofness.

[Chris Green]

So what anti-seize should one use on steel/aluminium threads?

[Chris Green]

None of the first lot I drilled out came out even when I had drilled a

6.5mm hole down the middle of the M8 grub screw. In many cases I had to use a punch to knock out the remains.

[Chris Green]

Fortunately I can get them off the window so I can take them home and I do have a pillar drill. It's quite laborious though and there's probably a hundred or more to deal with.

[Colin Bignell]

Would nylon do the job? If not you can get alumina ceramic set screws, but they are a bit more expensive.

[Tim Lamb]

Have you tried a hammer type impact driver? My 60 year old set still get some use:-)

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