Crumbling Monkey Metal

[Neil WyattModerator @neilwyatt]

I'm fitting a new body to a guitar I 'made' in 1993. It's got a Floyd Rose (or more likely a copy) bridge that dates back to about ten years earlier so it must be about thirty five years old.

It was hard to tune and when I removed it from the guitar the reason appeared obvious – the three fixing screws for the part inside the guitar was loose.

This does get a fair bit of stress taking the whole string tension, balanced by three springs. Especially when it was on my brother's strat in the days before I got it!

However, it seems the damage is not as simple as just stress cracks as the whole part is riddled with cracks that make it look like the whole part is swelling from the inside. My guess is it started to gradually swell and split due to tinworm and this then led to the actual breaking of the parts the screws fit into.

It's a pressure casting but I'm going to machine a replacement from 6062 aluminium alloy.

Neil

[Neil WyattModerator @neilwyatt]

[Tim StevensParticipant @timstevens64731]

A common problem with old diecast alloys – whether zinc based or aluminium based. From memory, it can be caused by a lack of purity in one or more of the alloying elements.

And you are right – the answer is to start again – fortunately in this case it seems a straightforward part to machine. Or do I mean straight forward, then back again, then sideways, and then endways …

Regards, Tim

Edited By Tim Stevens on 20/01/2019 11:51:02

[Chris TriceParticipant @christrice43267]

What Tim says. A lot of old die cast cars from some specific manufacturers have the same problem usually around rivets.

[Gray62Participant @gray62]

Doesn't look right for an original Floyd Rose, almost certainly one of the far eastern copies that were around at that time. IF your making a new block, I would recommend brass over any aluminium alloy. The block helps with sustain on a floating trem. I used to make these and most customers wanted a bigger block so they were made almost double the thickness of a standard sustain block. Floyd Rose now sell them as a replacement part. Is yours fitted with fine tuners and the double locking type?

[Brian HParticipant @brianh50089]

As Tim says, a common problem with old diecasts. Austin seven carbs are notorious!

Brian

[Howard LewisParticipant @howardlewis46836]

Some old diecasting just seem to turn to powder. Have an old Rivarossi loco that I dare not look at too hard for just that reason.

(Last week, a recent alloy Toilet Handle broke. The fracture was so full of blow holes that it looked like a silver painted Aero chocolate bar!)

No doubt, your shop made replacement will be far better than the original when new, and have an infinitely greater life expectancy.

Howard

[GeorgineerParticipant @georgineer]

It has the delightful name zincpest.

George

[Martin Hamilton 1Participant @martinhamilton1]

Some of the castings on old Emco machines can suffer with diecast corrosion problems after a number of years where they start to burst open. I looked at a 1979 Emco compact 8 recently & the leadscrew bearing blocks at either ends of the leadscrew were bursting & splitting open purely with age.

[Nicholas FarrParticipant @nicholasfarr14254]

Hi, it could have been an inspiration for Neil Diamond's song "Cracklin' Rosie".

I'll get me coat.

Regards Nick.

[not done it yetParticipant @notdoneityet]

It’s a reaction with water. Damp storage or just cold with a fair fair humidity will cause expansion of the cheap MAZAK. I’ve encountered this with north american autoknitter sock knitting machines. Probably why English made versions were fitted with cast iron cylinders and steel parts.

[BazyleParticipant @bazyle]

My search to find out what you were talking about led me to a site advertising 'build your own bridge'. Massive disappointment on finding it was the modern kids version of build something ie select the colour and trivial stuff.

Well at least my knowledge of stuff I will never ever need to know about has increased. If you machine your own at least you can boast 'machined from billet' when meeting cheapskates who only have a diecast one.

[vintage engineerParticipant @vintageengineer]

It's caused by hydrogen embrittlement. A naughty trick foundries do on aluminium castings is to add zinc to bulk out the aluminium. This comes to light when you try to weld the crap!

[Ed DuffnerParticipant @edduffner79357]

Neil, a preferred metal is 1018 cold rolled steel for trem blocks. I'm not sure what the equivalent of 1018 is here in the UK.

Ed.

[Neil WyattModerator @neilwyatt]

Posted by Gray on 20/01/2019 12:07:18:

Doesn't look right for an original Floyd Rose, almost certainly one of the far eastern copies that were around at that time. IF your making a new block, I would recommend brass over any aluminium alloy. The block helps with sustain on a floating trem. I used to make these and most customers wanted a bigger block so they were made almost double the thickness of a standard sustain block. Floyd Rose now sell them as a replacement part. Is yours fitted with fine tuners and the double locking type?

I'm pretty sure it's a copy, with fine tuners but old enough not to be double locking.

The guitar is a bit of a hack I just want to be pretty, I have plenty of rock solid guitars so one with feeble sustain might actually be a nice change – plus brass is expensive and I have the ally

I could get a brand new licensed one (as used on cheap Chinese guitars) with locking (and much simpler construction) for £11, but I like the challenge of making the part.

Neil

[Neil WyattModerator @neilwyatt]

Posted by Ed Duffner on 20/01/2019 15:02:26:

Neil, a preferred metal is 1018 cold rolled steel for trem blocks. I'm not sure what the equivalent of 1018 is here in the UK.

Ed.

Hmm could use steel. EN32 is probably close, but I'm sure EN1a would be fine.

Will need some sort of rustproofing.

Hmm will need an M10 x 1mm tap. I can make one that will do the job in aluminium but might struggle in steel. This was meant to be a cheap project but I've already had to buy a jack socket, a bottle of blue ink, three cans of polyurethane varnish, scratchplate material and the new body…

Edited By Neil Wyatt on 20/01/2019 15:45:36

[Neil WyattModerator @neilwyatt]

Posted by vintage engineer on 20/01/2019 15:00:41:

It's caused by hydrogen embrittlement. A naughty trick foundries do on aluminium castings is to add zinc to bulk out the aluminium. This comes to light when you try to weld the crap!

But where does the hydrogen come from?

[Nigel BennettParticipant @nigelbennett69913]

Mazak (Zamak if you're in the US) as used for a lot of zinc die-castings were very prone to crumbling away (Old Hornby Dublo stuff and many pre-war toys sometimes suffered). This was due to minute amounts of lead in the alloy causing grain growth. If the lead is below a certain concentration, there's usually no problem.

[SillyOldDufferModerator @sillyoldduffer]

Not a new problem. To read all about it see Zinc Pest

Dave

[davebParticipant @daveb17630]

Reminded me of an engineering firm who made motor scooters in the late 50s. The handlebar bracket was a Mazak casting, the handlebars tended to fall off.

[Neil WyattModerator @neilwyatt]

Agreed, it's zinc pest, not tinworm

Neil

[John ReeseParticipant @johnreese12848]

Posted by vintage engineer on 20/01/2019 15:00:41:

It's caused by hydrogen embrittlement. A naughty trick foundries do on aluminium castings is to add zinc to bulk out the aluminium. This comes to light when you try to weld the crap!

Fraid not. It is lead contamination that causes the zinc rot.

[Neil WyattModerator @neilwyatt]

Wikipedia has some interesting stuff on Zamak/Mazak it seems it's a range of metals developed specifically to avoid zincpest by using high purity zinc.

Perhaps we do it a disservice it by classing it as standard 'monkey metal'?

Neil

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Neil Wyatt on 20/01/2019 19:17:01:

Perhaps we do it a disservice it by classing it as standard 'monkey metal'?

.

I am certain that 'we' do, Neil

Just like with 'Loctite' … sloppy usage, and 'viral' opinion-forming have ridden roughshod over the manufacturers' good efforts.

MichaelG.

[VicParticipant @vic]

These lightweight cast “alloys” don’t need to be old to be useless. I’ve had to replace quite a number of parts on my Record Power belt and disc sander due to material failure after only a couple of years.

[Author]

Posts