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Old 8th Nov 2016, 10:20 pm   #1
Oldelectronics
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Default Immobile Woodscrews!

I have recently bought a Stentorian extension speaker the back which is held on with wood screws. The problem is they wont budge and in the past some have been a bit damaged.I have tried Servosol followed by WD40 to no avail!I dont want to be to rough as the Whiteley label is mostly intact.I wanted to clean the dust of ages from inside and check the wiring and speaker etc before connecting it to anything, I was wondering if heating the screw heads with my iron may expand and contract them or borrowing a mates Dremal to cut the slots deeper Or just polishing the outside and leaving it as it is if it works when connected to a AVO then a set? I cant work out why screws into what is probably pine wont budge so suggestions gratefully received!
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Old 8th Nov 2016, 10:44 pm   #2
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Default Re: Immobile Woodscrews!

Any that have the slot intact I would try hammering a correct sized screwdriver into the slot, then try Tightening if you can get it to move a fraction then try slackening if is still tight try tightening again. The screws with damaged heads may be best ground off when the back is lifted off try hammering the remains of the screws then attach mole grips and work the stub back and forwards until it is hopefully slack enough to screw out, if not cut off flush and put another screw down the side of the original.

Good luck with it, John

Ps, did you make that one originally ?
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Old 8th Nov 2016, 10:53 pm   #3
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Default Re: Immobile Woodscrews!

Thanks for that John I will give them a try. I admit I did buy it for nostalgic reasons but this model was made about 1949 and I started work there in 1965.

cheers

Kev
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Old 8th Nov 2016, 10:54 pm   #4
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Default Re: Immobile Woodscrews!

Impact driver in reverse sometimes works.
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Old 8th Nov 2016, 11:04 pm   #5
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Default Re: Immobile Woodscrews!

The importance of a sharp screwdriver blade which accurately fits the slot cannot be over emphasised. Rounded corners and tips are out. Cutting the slot deeper can help if that's possible.

I have been known to use miniature mole grips on the screwdriver's shaft to increase torque.

Sometimes you can grip the screw head with a pair of sidecutters pointing along the axis of the screw.
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Old 8th Nov 2016, 11:05 pm   #6
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Default Re: Immobile Woodscrews!

Plenty impact drivers about but personally I have never had success with them, especially on wood. My son has a battery impact driver, the type you use on wheel nuts, He recently dismantled some old machinery with very rusted threads without shearing any bolts. I just wonder if on its lowest setting and suitable reduction from the .5 inch drive to a screwdriver bit it would work.
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Old 8th Nov 2016, 11:14 pm   #7
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Default Re: Immobile Woodscrews!

Red hot poker on the head, of the screw that is. Slight burn loosens the remains.
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Old 8th Nov 2016, 11:38 pm   #8
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Default Re: Immobile Woodscrews!

I would echo the need for a properly-fitting screwdriver blade. My experience is that some sizes of older woodscrews have slots that are not a good fit with modern screwdriver blades, whereas the old wooden-handled screwdrivers inherited from my dad are a snug fit. I have sometimes had to resort to re-grinding a screwdriver blade to ensure I had a square sharp-edged blade of the correct thickness that would engage the bottom of the slot rather than camming out.

Looking a the photo, the slot is not very deep, and could well benefit from deepening, but if you make it too deep, the head (or often half of the head) could shear off. Once the sides of the slot become sloping, you are on a hiding to nothing. I have used a thin carborundum disc on a Dremel-type drill for deepening the slot in this sort of countersunk screw. Petrol lighter fluid is much more penetrating than WD40, or Plus-Gas if you can find some. The red hot poker sounds like a good idea to try.
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Old 9th Nov 2016, 12:13 am   #9
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Default Re: Immobile Woodscrews!

good drop 3/1 oil on the screw heads over night should help..
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Old 9th Nov 2016, 7:11 am   #10
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Default Re: Immobile Woodscrews!

You can buy a paste, rather like grinding paste, which increases the grip of the driver in the screw head. Sorry, I don't remember what it's called off hand, but no doubt a search would turn it up.
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Old 9th Nov 2016, 7:19 am   #11
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Default Re: Immobile Woodscrews!

Traditionally a red hot poker was used for this task, but I have had success with a big Solon soldering iron.
Don't use WD40, that's not designed as a release agent and a Dremel shouldn't be necessary.
As said above, a properly fitting screwdriver is essential, and work with the screws vertical so you can apply pressure. Tightening first usually works.
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Old 9th Nov 2016, 7:36 am   #12
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Default Re: Immobile Woodscrews!

Brass screws + pine + decades of time = corrosion = great difficulty in removing the screws, that's what the problem is! There's 'glue' (sap) in pine, and this interacts with the corroding brass to form a formidable bond. So the screws will have 'grown' into the surrounding wood. If the screws are brass - they look it - then even using a very sharp screwdriver etc you may find that the pressure needed to break the corrosion 'lock' is greater than the tensile strength of the screw; it will shear at the shaft or one side of the head will break away. Nonetheless, that is your first port of call, to try your best to turn the screws out normally. If that fails then I would carefully drill away the head of the screw, lift off that cover and use mole grips to turn and remove the screws. Only then will you truly see how hard they are locked in place; they may shear (again). In which case it's a question of more drilling with a fine drill and gradually 'teasing' the screw out with whatever tools you can muster to move/turn it. Try to move/waggle it side to side, whatever, to loosen its grip. It may not be a pretty job to do, but the result may be that you just need some new screws. Brass ones are easily 'aged' by leaving them outside for a few weeks to oxidise, go dull. Ease the new brass ones in with some vaseline on the threads, having used steel ones first to recreate/clean the threads.
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Old 9th Nov 2016, 9:24 am   #13
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Default Re: Immobile Woodscrews!

Hi Guys thanks for the tips I will start with the less destructive first and work through them but some great ideas. I will report back when/if I get them out.The screws are steel but the cup washers they sit in I think are brass.

Thanks again

Kev
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Old 9th Nov 2016, 9:40 am   #14
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Default Re: Immobile Woodscrews!

If no go with a screwdriver then grind/cut/tear or whatever those cup washers off, replacements are readily available, then mole grips or bull nosed pliers on the screw heads.

Lawrence.
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Old 9th Nov 2016, 10:38 am   #15
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Default Re: Immobile Woodscrews!

After years of mucking about with soft brass screws that don't want to move, if I can't get it to undo after filing the slot square and using an impact driver, I don't waste any more time. Drill the head off, pull the panel or whatever off then unscrew the remainder of the screw with mole grips. If it won't come out then cut it flush and drill that out too. Then refit with a new screw - if originality isn't important, I'll use a Pozidrive so there's more chance of getting it undone in future.
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Old 9th Nov 2016, 1:08 pm   #16
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Default Re: Immobile Woodscrews!

I have got them out useing a combination of a Dremal type device to deepen the slots various screw drivers and a pair of side cutters to cut away the cup washers on most of them the problem was the cup washers had dug into the hardboard and the screw had corroded to the cup washer the screw would then with difficulty turn but would not unscrew so enter side cutters again to slide under the head to lever out the screw! After the back has been polished & replaced it will be secured with flat washer!
Thanks for all the helpful suggestions

regards

Kev
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Old 9th Nov 2016, 5:46 pm   #17
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Default Re: Immobile Woodscrews!

I decided to go with the original brass cup washers but used number 6 crosspoint screws instead of number 4 slot heads and put silicon grease on the threads so hopefully this problem wont recur not to original but would have looked not dissimilar when new? Just the edges to do now with the polish and electrically it seems fine? Although may have been kept somewhere a bit damp?
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Old 9th Nov 2016, 6:04 pm   #18
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Default Re: Immobile Woodscrews!

Loctite thread locking stuff is useful when reassembling (it does work with wood too), it is designed to stick parts together somewhat weakly, an odd choice one would think but... It seals the parts from moisture and corrosion and they will always come apart with a small amount of force.
 
Old 9th Nov 2016, 6:46 pm   #19
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Default Re: Immobile Woodscrews!

Very well done on succeeding in getting the screws out Kev.

On occasions, when all else has failed, and the screw head has been chewed up, I've had to resort to using a long 'plug cutter' to remove a plug of wood along with the screw, then have glued a dowel into the hole and drilled the dowel to accept new screws; EG:

http://www.powertooldirect.co.uk/tre...5-p-63338.html

The original screws in your extension speaker look to have been slotted 'raised head countersunk' - not flat, not round, but 'raised'. If you fitted cross-point screws because you didn't have any raised head brass countersunk to hand (who would have?), and wanted to fit replacement screws which are identical or similar to the originals so to preserve the originality, they're readily available and not expensive. These for example, are available in a wide range of sizes and if you wanted #4 they come in several lengths - 1/2", 5/8", 3/4" and 1". The smallest pack size is 50, but they range from £2.85 for pack of 50 1/2" ones, to £3.50 for 50 1" ones, (post free) 'buy it now' from a UK supplier:

http://www.ebay.co.uk/itm/TQ-Solid-B...-/360952371525

Hope that's helpful.

As an aside, extension speakers such as yours are an interesting facet of socio-economic history - to me, at any rate.

They date from an era when radios were so expensive that it was unthinkable to have more than one in the house, so extension speakers enabled the radio to be 'piped' to more than one room. (It's also why so many radios were 'transportable' from room to room, such as the Coronation Twin, KB FB10 toaster, Stella 105U). I have a nice Whitley Stentorian 'Baby X' extension speaker with the original price pencilled underneath - £3.18.11d. I'd take a guess at circa 1955, and that price today equates to the not inconsiderable sum of £94.00, so even extension speakers weren't a cheap acquisition.
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Old 9th Nov 2016, 7:58 pm   #20
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Default Re: Immobile Woodscrews!

'Get that thing off my draining board!'

For future reference, a pin punch and a left handed drill bit can be used as a persuader particularly where the screws are brass. With steel you do end up snapping one or two drill bits. All you need is one of those low geared chest drills- you know, the ones the size of a tommy gun. Drill bit needs to be half way between 'sharp' and 'blunt' and a suitable angle ground on the end helps.

Re WD40, personally i do rate it as a penetrating agent, (where metal on metal is concerned, at least) I trialled it against diesel, paraffin, jet fuel and 3 in 1, and it came out on top by a good margin. Plus gas is as good if not better.

3 in 1 Graphited (yellow can) stands out by virtue of it's uncanny ability at removing the glue from uber-sticky labels, but without the stink of petrol or meths. I just hope it's still available.
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