Moore & Wright disaster

I recently came into a somewhat rust-pocked but otherwise OK pair of Moore and Wright dividers. I had a basin of commercial kitchen descaler/pickle handy, and I've noticed that it works very well as a rust remover, so I dunked the dividers in, and used a brush to cover them in the liquid. They were there for a few hours and I slopped the liquid over the bits poking out every half hour or so and turned them over. The rust was rpaidly disappearing/truning that healthy blue-grey colour and teh chrome staying bright. All well and good.

Then - "Oh My Golly Gosh!" one time I turned them over there was a gentle click and the spring had split right across where the handle is riveted into it.

I'm assuming there must have been a pre-existing crack, possibly with some corrosion in it. I have used them without noticing any problem several times. Is it possible that mild acid can cause a crack to propagate?

I'm hoping I can silver solder the spring and re-temper it in one go.

Neil

That little bit of rust can sometimes be all that is holding something together look at Mini Metro's

A long time ago I used to do a lot of auto welding mostly with MIG/MAG, you could weld up the floor of your aforementioned Metro only to find once the adjcent rust had "dried out" you had further splits/holes to plate over.

Paul

Hi Neil,

I have no experience with rust removal as such. However, compared with a smooth surface, a pitted surface is likely to be weakened when placed in tension or when flexed, as it has to in the case of your divider spring.

I doubt very much, that silver solder will be strong enough. The spring's `elastic' properties will also be lost at the temperature needed to melt silver solder. I could imagine that someone very skilled at (micro) welding, might affect a repair. Then you'd have to heat treat (harden and temper)again. With respect, it hardly seems worth the effort.

If you can't get a replacement spring, it would be better to make a new one.

Hope this makes sense. It's very early in the morning, and my brain isn't working fully.

Best regards,

Sam

Neil,

Yes the acid can cause the crack to propogate, and the process seems to escalate exponentially.

The mechanism is known as Stress Corrosion, and you will find an excellent article on Wikipedia.

... Sorry for your Loss.

MichaelG.

Hello again Neil,

I'm back from my walk and breakfast is inside me, so I'd like to concur with Michael's comments and add a couple of extra remarks just for interest :-

Although it may be too late to tell, but the fractured surface often reveals that a crack has been propagating for some time. The darker edges of the fracture, compared with the brighter patch at the moment when failure occurred, are the usual (but not always) signs of crack propagation.

When stressed either in tension, or worse in flexure (bending), the reduced cross-sectional area clearly offers less strength. In flexing, as you can appreciate, there are both tensile and compressive forces involved. It's the leverage (from bending), and the tensile forces which come into play which cause rapid failure.

If you want something to break, then a notched surface (knife cut), followed by bending is one of the simpler ways. For example, watch what happens when a glazier is cutting glass.

To digress even further, having worked in the plastics industry for more than fifty years, I'm very conscious of the `sharp notch' effect, and the ensuing failures.

It's the scourge of the plastics industry.

Now I'm rambling, so I'll stop before someone tells me to.

Best regards,

Sam

The corrosion in the spring steel goes intercrystaline, and the steel becomes embrittaled, the same thing happens when using galvanic (electric) rust removal. 'Fraid higher carbon steels can be a bit of a problem when it comes to rust removal. Ian S C

With galvanic rust removal it is the hydrogen that does the damage, otherways known as hydrogen embrittlement.

Predictions of furher doom were appropriate. I couldn't find any easyflo flux so I used borax, but I managed to get decent penetration. As it was wired up, I was able to raise it to a decent red and quench. Some of the soft galvanised iron wire ended up bondd to the steel, filing it off proved the string was glass hard. I tempered down to purple, and it regained its spring so I was really cheerful.

But the strain of opening up gfor re-assembly popped the silver solder joint

I might have a go at welding it, but with me the blob of weld will be half the size of the spring!

Neil

Neil, your not going win on this one as whatever you do will be weak and go again.

I have a couple of dividers that have been mangled and no use to me, give an idea of the size of the spring and if its near the size of mine you can have them gratis.

Clive

Hope, somebody will have an answer for me; I already mailed Moore & Wright about this but got no answer.

I happen to have one of those old digital Micro 2000 micrometers, the battery needs to be replaced, who can help me out with a source for this?

.

Paul,

Sit down and breathe deeply ... then look here

If it's an early model, you will probably also want a glass of Malt.

... I think you may need to do some creative modification.

MichaelG.

Paul,

I just found this thread, which contains some useful information.

MichaelG.

Hi Paul,
You do not give any details of the battery you require. (dimensions and number of cells / voltage.) Here is a possible source of supply but you would need to see if they have one that fits.

Les.

Thank you Michael!

I am not very good with electronics, mine does work perfect when attached to its loader so that is not a problem.

The very nice thing is that there is a constant pressure when measuring, so hardly any fault readings and that is why I would like to use mine again in a normal way- not bound to a wire.

I will have some more malt and think about the costs of the battery replacement.

Paul,

As Les said ... it would be useful if you could give details of the battery.

If it's the original Micro 2000, then it should be 4.8v [a stack of four 1.2v cells], which should be reasonably simple to substitute ... but we need the physical dimensions.

It's a truly great instrument, so let's get it fixed !!

MichaelG.

Hi Neil ,If you have the bat. no "battery trader " seem to have a battery for anything.

Let us know how you get on and best of luck Maurice.

The battery are 2 stacked coin cells, each stack is built-up from 2 coin cells in crimp-foil. On the foil is printed HW1 70K2L, 2.4V , 170 MAH.

Thanks for that Paul

I'm sure that, between us all, we can find something.

MichaelG.

Outside diameter is 25.2mm, one stack of 2 coin batteries has a hight of 13mm, sorry about this, I should have written down the dimensions right-away!

Paul,

Two of these would get you pretty close.

... Just need to trim the terminals ?

MichaelG.

.

Edit: maybe easier to use four individual cells ... identified on the datasheet.

Edited By Michael Gilligan on 31/07/2014 12:16:54