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vinrads 20th Mar 2021 10:18 am

Rusted in grub screw.
I had two small knobs both with rusted in grub screws, I filled the hole that the shaft fits into with wd 40 left it for an hour or so ,applied heat to the screw with my soldering iron tip , inserted a good fitting screw driver, managed to to turn it a little then with a rocking motion whilst giving it a squirt of wd got it free, this worked well on both knobs , Mick.

Julesomega 20th Mar 2021 12:12 pm

Re: Rusted in grub screw.
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I rely on penetrating oil for almost every mechanical job: must be about a decade since it inexplicably disappeared from the hardware shops and market stalls, but I found it is now exclusively sold online as Omega 636.
For jobs like grub screws, a squirt is far too much so I pick up a minute drop with fine tweezers

merlinmaxwell 20th Mar 2021 1:32 pm

Re: Rusted in grub screw.
After a bit of soaking I use a left hand drill bit, worst case it drills out the screw, best case it jams and unscrews it.

emeritus 20th Mar 2021 3:48 pm

Re: Rusted in grub screw.
Petrol lighter fluid is almost as good as penetrating oils like Plus Gas and easier to buy.

Mike Phelan 22nd Mar 2021 4:39 pm

Re: Rusted in grub screw.
A mixture of diesel fuel and white spirit is what I use.

DonaldStott 22nd Mar 2021 9:08 pm

Re: Rusted in grub screw.
Thanks to this Forum I am now a convert to PlusGas for any job of this kind.

G6Tanuki 23rd Mar 2021 1:30 pm

Re: Rusted in grub screw.
PlusGas has been my 'go-to' for the last 45 years - the biggest problem I find with it is the tendency of the solvent-component to evaporate from the can whilst in storage. I never seem to use-up a can of the stuff, it escapes into the wild when my back is turned.

The heated-screwdriver-tip is another technique worth remembering: I've got a couple of old screwdrivers here whose tips I'm happy to heat until red-hot in order to put some heat into a tight grubscrew.

Bazz4CQJ 24th Mar 2021 8:20 pm

Re: Rusted in grub screw.
Hee Hee - Our periodic "let's bash" WD40" thread ;D. The reality is that the best releasing agent is time-dependent. If you only have 10 minutes, product A is best, but if you have 3 days, product B is best. I find my hand goes to the WD40 can, but there are always quite a few alternatives on the same shelf.


Mark1960 28th Mar 2021 6:56 am

Re: Rusted in grub screw.
WD40 is great as a water dispersant, but plus gas is better for penetrating rust.

Did it really take 40 attempts to come up with the best formulation?

David G4EBT 28th Mar 2021 9:06 am

Re: Rusted in grub screw.
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The main shortcoming of WD40 as a release agent is that as a water dispersant (it's original purpose) it has high surface tension - the opposite of what is needed for freeing stuck screws and nuts, which is capillary action to penetrate. WD40 (the company), have tacitly accepted that whilst WD40 has for decades been seen as a 'toolkit in a can' for everything from stuck screws to oiling hinges - even for arthritic knees, it doesn't do most of the tasks for which it's pressed into service all that well. That's why they introduced their 'Specialist' range of nine products, one of which is their 'Fast Release Penetrant Spray', about which WD40 says:


Our Specialist Fast Release Penetrant spray specifically targets corroded or rusted components and mechanisms. Its [sic] formula loosens stuck or seized parts quickly and easily. The penetrant has an extremely low surface tension, meaning it can cut through rust, seams and tightly-bonded threads to easily saturate and lubricate seized fixings. The Smart Straw and 360 valve allows it to be used precisely at all angles, and the capillary action of the formula means it can reach tight and hard to reach spaces. Highly water resistant, Fast Release Penetrant can also displace moisture that may be disrupting smooth movement and can be used as a preventative to prohibit the build-up of rust and corrosion in the future. Use in temperatures ranging from -20C to +90C, on materials such as metal, rubber, plastics, alloys and most paints.

End quote.

If they had a proof-reader to check the above text, they overlooked the 'Grocers' Apostrophe on the first line 'It's formula'. (There's a lot of it about!).

The Specialist range of WD40 products (as well as their Motorbike and Bike Ranges), can be found on their website, here:

I guess most of us use WD40 for all sorts of things, myself included - removing labels, degreasing, oiling locks, whatever. About the only thing I don't use it for is freeing stuck grub screws or anything else to do with radio restoration. Why would I want to use WD40 on grub screws when a can of Plus Gas lasts for a decade or more?

For those who prefer WD40 products, their Specialist 'Fast Release Penetrant' is widely available and not all that expensive. EG:

Pic 1) Why not? It gets used for everything else!
Pic 2) Engineering Flow Chart.
Pic 3) I even use a can as a radio!

merlinmaxwell 28th Mar 2021 12:17 pm

Re: Rusted in grub screw.
I want one of the radios!

rambo1152 29th Mar 2021 3:52 pm

Re: Rusted in grub screw.
1 Attachment(s)
I respectfully disagree with David's flowchart, and offer this alternative.

Attachment 230444

vinrads 29th Mar 2021 3:58 pm

Re: Rusted in grub screw.
All I can say it worked for me the wd oil turned a dark brown after a while ,and it helped to loosen the screw, Mick.

Oldcodger 18th Apr 2021 9:45 pm

Re: Rusted in grub screw.
I once heard of a penetrating solution based on paraffin with graphite grease dissolved in it.
If the screw is really stuck then perhaps it's time to look at a more extreme engineer solution- helicoil. Drill the screw out, re tap and fit.
As for #12, I tend to use blue locktite.(you never know when you need to get that screw undone)

The Philpott 19th Apr 2021 3:21 pm

Re: Rusted in grub screw.
Blue loctite also tends to inhibit future rusting.

telstar 21st Apr 2021 1:14 pm

Re: Rusted in grub screw.
I once heard of someone using a hot soldering iron to heat the rusted grub screw (Bakelite radio knobs only, of course).
Maybe this could work?

The Philpott 21st Apr 2021 4:13 pm

Re: Rusted in grub screw.
Most certainly heat works where other methods fail, (although with the example of a steel screw going into works by carbonising the wood!)

G.Castle 3rd May 2021 7:08 am

Re: Rusted in grub screw.
My "go to" now is Loctite "Freeze and Release" not sure about the freeze part but an excellent penetrant and safe on plastics.

I prefer Duck Oil for lubrication and protection as it's wax based and doesn't evaporate away completely.

emeritus 3rd May 2021 10:25 am

Re: Rusted in grub screw.
Heating or cooling will work best where two different metals are involved, making use of their different thermal expansion coefficients (TEC). The approx. TECs for brass and steel are 18-19 and 11-13 respectively. So for a steel screw in a brass bush, heating will enlarge the hole on the bush by more than the increase in diameter of the steel screw, making the fit looser. Conversely, for a brass screw in a steel bush, cooling in a freezer would be required, as applying heat would make the brass screw expand more than the bore in the bush, making it tighter. In the latter case, or where screw and bush are of the same type of metal, if corrosion is present, there might be an advantage in heating due to differential expansion of the corrosion products loosening them, but it would be necessary to cool it down before trying to unscrew. Differential expansion will be much greater when one of the items is aluminium (TEC = 21-24). Replacing a cracked alloy piston in my car involved heating to about 140C in an oil bath, whereupon the steel gudgeon pin dropped out under its own weight. At room temperature it was an immovable interference fit. Thus heating is likely to work with a steel or brass screw in an aluminium bush.

clockman 8th May 2021 5:00 pm

Re: Rusted in grub screw.
I also find that penetrating oil helps in removing those cabinet spring clips. AND is there a tool for doing this without braking the plastic stems ?

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