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repairing Mazak castings


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I decided to try Lumiweld to repair a crack at the base of the mounting-leg of a wiper-motor.  Motor was bought incomplete for spare parts for just a few pounds,  so I didn't have much to loose.  In fact I had a useful armature and field coil from it.

Mazak has a low melting-point and gives no sign of it's temperature, it just sags and runs away.

Lumiweld is an alloy with a melting-point lower than Mazak but NOT by much.

At this place the mounting-leg is nearly 12mm in diameter and the bowl that surrounds the gear is about 2mm thick.  So without protection, torching this will just melt the bowl before the Lumiweld will bond to the leg.

I used aluminium foil to keep heat away from the bowl and heated the leg.  Foil came from various dairy products.  This is so effective as a heat-shield, that I had to expose more of the leg, to get anything to melt at all.

As soon as the Lumiweld mixes with the leg, the pool has the lowest melting point, so you can reduce the heat and work it into the bowl.

Mazak often has bubble inclusions which burst when heated. You can see this on the bottom of the bowl.  Pock marked like little moon-craters.

Lumiweld is very strong and easy to use on Aluminium.   On Mazak you really need thicker parts and definitely not a mixture of thick and thin.

But I did it anyway!

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Very nice Alan.

Clearly your thoughtful preparations and skills can lead to a very nice result.

Waldi

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As you say Alan, mazak gives no indication that it is near its melting point - one moment it is there and the next a puddle on the bench. You obviously have the process well under control.

It is possible to soft-solder mazak, which poses less of a danger to the item but of course is not as strong as Lumiweld. Useful for filling holes and mending non-stressed areas though.

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Working outside in bright sunlight helps.  You can just spot a slight surface change, kind of dulls,  before it goes saggy. (See how I shined it with a stainless-steel brush to make this more evident).

But you want no wind to mess up the heating.

You use a piece of thin stainless-steel wire with a L-shaped bend and filed into a wedge shape.

Place a cut off piece of Lumiweld on the crack. Melt it and wiggle it about until it merges with the Mazak.  Back-off heat and spread it about.

This is tricky.  Watch where you point the torch while wiggling.  Just a bit too much heat and it's game over on thin stuff.

Edited by AlanT
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