How to remove seized screws in a Clarion Cassette Mechanism?

['LIVEWIRE?']

Perhaps seized isn't the right word, but I couldn't think of a better one. Having removed the mechanism from a Clarion/Jaguar Radio/Cassette player which must be 40 years old, I am attemting to remove the base plate in order to change the drive belts. I was able to undo two of the four screws without much difficulty, but the other two are firmly stuck, never having been undone since the mechanism was made. They are small, possibly M2.5 screws with pozidrive cross=point heads, and I'm likely to ruin the heads trying to loosen them. At the moment I've left them, having sprayed WD40 round them in the hope that this will free the screws, otherwise I'm going to have to drill off the heads (unless anyone has a better idea?)

[ms660]

Countersunk or pan head?

EDIT: If pan head try side cutters, jaws at 90 degrees to the head, always worked for me.

Lawrence.

[paulsherwin]

You could drill the heads off, as you say. Should be straightforward.

WD40 isn't the best product to use - specialist dismantling fluids like Plus-gas are better.

[G6Tanuki]

Heat the heads with a soldering-gun. Not an iron, a gun. In the past I've used one of the brute-force Weller ones with a chunky trigger-activated transformer in the handle and a loop of thick copper wire as the 'bit'.

You need to get a lot of focussed heat into the screw-thread.

[This method works well too on the 40-year-old screws used to hold the metal screening-plates you find on old CRT-based computer-terminals]

[TonyDuell]

A trick that has often worked for me (and coincidentally was mentioned in this month's 'Clocks' magazine) is to try _tightening_ the screw. Just use the right tool, turn it clockwise almost as hard as you dare. then try unscrewing it as normal.

[paulsherwin]

Yes, that does often work.

[AC/HL]

I'd have thought that they would be Philips head rather than Pozi?

[Ted Kendall]

The screw heads are almost certainly JIS, which is subtly different from Pozi or Phillips, identified by a little indentation by the slots and used throughout Japanese kit. Use an appropriate driver and they will very likely unscrew without trouble and without chewing the heads up.

[emeritus]

Petrol cigarette lighter fuel, such as Ronsonol, is significantly more penetrating than WD40.

['LIVEWIRE?']

Despite having 2 or 3 sets of bits for my Screwdrivers, plus several individual drivers of various types, I don't have any JIS bits. Somehow I've managed without them for over 40 years, and can't say I've ever even heard of them till now, during which time I must have repaired & serviced many Clarion and other Japanese Car Stereos.. I guess it's about time I bought some JIS bits! I'll try some Ronsonol on the affected screws, too.

[SiriusHardware]

I'd never heard of JIS either until James May started banging on about it in one of the episodes of 'The Reassembler'. But I do remember often having seen Posi / Philips - like screws with a little hollow dot in the space between two arms of the 'cross'.

[Ted Kendall]

The essential difference between JIS and the others is that it does not provide for "camming out" if excess torque is applied - this affects the driver profile and hence the fit in the screw head.

[Goldieoldie]

I use heat from soldering iron, then plus gas, then heat, then Plus Gas.
Leave to cool then try unscrewing.
You will know you have heated the screw enough when the plus gas starts to smoke!

[AC/HL]

Originally Posted by Ted Kendall

The essential difference between JIS and the others is that it does not provide for "camming out" if excess torque is applied - this affects the driver profile and hence the fit in the screw head.

I suspect a few of us have learned something here

[Radio1950]

Hi Livewire

some good advice in posts so far.
Make sure that no thread locking lacquer or similar has been used on the threaded end opposite the heads. If so, and if possible, use an "aggressive" solvent (or heat) to soften it overnight first.

I sometimes have success with a powered screwdriver on light clutch, which acts as an impact driver. Need to hold it firmly in the screw head.

I believe one manufacturer of screwdrivers (Vessel? or Wiha?) made a special Pozidriv which acted as an impact driver when rapped on the handle end with a very light hammer.

I now use a pair of Fujiya screw pliers for problem screws, if you can get the jaws in. Very good indeed.

Don't worry too much about JIS heads. Japanese made radio etc is full of them.
I ran across them years ago, and I just use Pozidriv drivers, finding one driver size which fits snugly.
Last time I searched for JIS drivers, whilst working on a JRC RX, only one manufacturer was making them, and I think the driver points were actually a compromise of JIS and Pozi.

For Australian members, Jaycar stock the screw pliers.
And my stocks of M3 and M4 RH screws from both Jaycar and Altronics have the dimple in the head, but I suspect they are all actually Pozidriv head.

Good luck.

[PsychMan]

Its a bit brutish, but I tend to use a dremel with a cutting disc, and cut a deep flat blade slot into the screw heads. If its countersunk it doesn't bother me if its not in a visible area, minor collateral damage

I find you can get more purchase on it that way. You can then replace the screws, or simply put the "modified" ones back if you cant be bothered to find replacements

[DonaldStott]

Originally Posted by paulsherwin

WD40 isn't the best product to use - specialist dismantling fluids like Plus-gas are better.

It's a well known fact that the “W-D” in WD-40 stands for Water Displacement although it does contain a blend of lubricants.

I've been a convert to PlusGas for many years now having had more success with freeing seized screws, bolts etc. PlusGas was especially useful in helping to remove the small screws from an HMV No 4 Soundbox.

Didn't know anything about JIS screws so I've also learned something new today: -

https://chapmanmfg.com/blogs/news/ph...the-difference

[Station X]

A trick I've used is to hold the screwdriver bit in the chuck of a drilling machine. It's then possible to apply axial force using LIGHT pressure on the drill's feed handle, which prevents camming out. The chuck is then rotated by hand.

I learned this trick after seeing the tool used to remove the field windings from Lucas starters and dynamos. Let's not discuss that here though.