Lock won't Unlock – sorted: New key v Old

[Scoosh]

I have an old (50yr+) wooden under-bed box with a simple lock and key.
This has always opened no problem... until last week. The key turns nice and easily as usual but it won't go all the way to unlock.
I've tried gently lifting/ pressing down on the top ... but the key still won't go all the way round.
The is the key :

Viewed from the underside, it doesn't show any sign of a piece having broken off – all the lugs are the same dark colour.


I'm hesitant to use too much force for fear of breaking it off inside the lock.

Anyone know enough about locks to help me get into the box ?

 

[bluenotebob]

A swift blast of WD40 usually works

 

[Scoosh]

Aye, I've tried WD40 but no joy.
The key goes in fine, turns 90*, then I can feel it picking up the locking part, then it goes to 180* but not over the final 90* to unlock.
The lock itself feels very 'loose' and certainly not too 'tight' – there is no more than usual gentle pressure required to turn it through the initial 180*... at which point it just stops.

My initial thought was that one of the lugs of the key had sheered but, as the pic shows, there is no bright edge to either of the two lugs.
The puzzle continues...

 

[classic33]

Have you tried pushing the lock closed as you turn the key to open it.

The deepest cut on that key looks worn.
Is there anything in the key that is preventing the key from sitting on the pin fully?

This type of lock?

 

[grldtnr]

Had the same problem with a mortice lock on an internal door, wiggled a credit card to slip the lock, got it off and disassembled it.
Inside there was a bit of sprung steel, it had broken, couldn't repair it, shame as it was a 'period' piece.
Back ton your problem, likely you will need to wiggle a thin blade in your lock, perhaps you have the same problem as I?

 

[Ming the Merciless]

Do NOT open Pandora’s box …

 

[chris667]

Do NOT open Pandora’s box …

...not without buying her a drink first?

 

[HLaB]

Aye, I've tried WD40 but no joy.
The key goes in fine, turns 90*, then I can feel it picking up the locking part, then it goes to 180* but not over the final 90* to unlock.
The lock itself feels very 'loose' and certainly not too 'tight' – there is no more than usual gentle pressure required to turn it through the initial 180*... at which point it just stops.

My initial thought was that one of the lugs of the key had sheered but, as the pic shows, there is no bright edge to either of the two lugs.
The puzzle continues...

I had a D'Lock once I literally had to bathe in the stuff (well actually GT85) but with the help of a colleague I did use force. Bizarelly after a right good soaking it worked perfect for several more years until I had to change jobs mid covid leaving the lock at the old place.
Another time I needed open a pad lock that was seized and I similarly bathed it in GT85. Whilst at first it wouldn't budge a few days later it opened without force.

 

[twentysix by twentyfive]

 

[classic33]

View attachment 697553

Don't think he wants to damage the box.

 

[Scoosh]

Do NOT open Pandora’s box …

... but it's got my summer clothes in it !
... and summer might arrive soon !

Have you tried pushing the lock closed as you turn the key to open it.

Not sure what you mean – the top of the lid overhangs the edge of the box, so I can't get at the actual lock, as the lid is pretty tight on the box, in its correct position.

The deepest cut on that key looks worn.

Yes, that was my initial diagnosis.

Is there anything in the key that is preventing the key from sitting on the pin fully?

Nope, key goes in smoothly, turns 180* but won't go the last bit to unlock.

This type of lock?

Don't know – can't see it atm but the keys look very similar.
My lock has the keyhole at right angles to your picture but otherwise ... it could be similar but I don't really know !

My latest thought is to get another blank key and try to file it down to fit.
This kind of thing:

 

[classic33]

Try fitting the key in the lock, keeping the key straight by forcing it to the rear plate, and turning slowly.
If the pin is loose, it should help with lining the key up with the levers inside the lock.

Before you do this, check the hole in the end of the key. Is there anything in there, preventing the key going in fully.

It is a surface mounted lock and not a padlock?

 

[Scoosh]

Is there anything in there, preventing the key going in fully.

Nothing preventing the key going in fully – just a bit of rather dirty WD40 !

Try fitting the key in the lock, keeping the key straight by forcing it to the rear plate, and turning slowly.

No joy there.

I'll get along to a local locksmith and get a replacement key, then file it down slowly until it fits/ works.

 

[Scoosh]

Thanks to everyone who has assisted.

I hope to add a final post of SUCCESS !!!

 

[classic33]

Have a look for a similar keyed lock in the shops, having taken your current key with you. 1 in around 125 chance of getting another, new lock, with the same key.

You might have trouble getting a blank, illegal to sell one.