Bubbles in cast iron

[michael howarth 1Participant @michaelhowarth1]

I recently bought a wheel casting and on machining I found that there was an air bubble just where you don’t want it. At the junction of the tyre tread and the rear flange. I called the supplier who couldn’t replace it because he didn’t have any in stock. I could have pushed it and waited until they came back into stock but the proprietor did offer a solution. He told me to put the wheel on a metal plate and heat it up from below (I used a camping gas burner). Meanwhile, mix up some araldite and add some cast iron dust to it (plenty all over my lathe!). Then add the Araldite mixture to the hole in the casting. To my surprise, on contact with the hot surface, the Araldite mix flowed like water into the hole. When the casting cooled down the Araldite had completely hardened but I waited another day before resuming machining and obtained a very good result with just a slight colour difference between the casting and the filler. This tip is probably known to many but it is the first time I have heard of it and I hope  it may be useful to others.

Mick

[HopperParticipant @hopper]

First time I have heard of it. Sounds like a very useful tip. Thanks for sharing.

[Robert Atkinson 2Participant @robertatkinson2]

Basically DIY JB Weld or Devcon

[Robert Atkinson 2]

On Robert Atkinson 2 Said:

Basically DIY JB Weld or Devcon

or even this,

https://uk.rs-online.com/web/p/adhesives/0850962?gb=a

Metal Loaded Epoxy, although when cured the colour is nearer to black than grey

Ian P

[michael howarth 1Participant @michaelhowarth1]

I appreciate that metal loaded epoxies have been around for quite a while. It was the method of use that impressed me – the simplicity of heating  the workpiece and the subsequent dramatic reduction in the viscosity of the epoxy when it came into contact, allowing it to flow into and filling the cavity rather than trying to poke a stiff mixture in.

Mick

[Ian P]

On Ian P Said:

On Robert Atkinson 2 Said:

Basically DIY JB Weld or Devcon

or even this,

https://uk.rs-online.com/web/p/adhesives/0850962?gb=a

Metal Loaded Epoxy, although when cured the colour is nearer to black than grey

Ian P

That does not contain metallic particles…..
see https://www.model-engineer.co.uk/forums/topic/metal-loaded-epoxy-what-metal-is-used-in-it/

[Ian PParticipant @ianp]

My reply was a bit tongue in cheek Robert as I knew there was no ‘real’ metal in the RS product, the only metal is in RS’s marketing title.

Mick’s experience with applying epoxy to a heated surface is an interesting subject, in my understanding I would have thought the elevated temperature would have cured the epoxy too fast for it to reach its full hardness. I can see an experiment coming on….

Ian P

 

[Clive Brown 1Participant @clivebrown1]

Sensible temperatures shouldn’t affect the final cured properties and warmed epoxy will flow very easily, with a useable working time window. IIRC, in the ’70’s(?) ME carried an article by someone who successfully sealed the tanks of a loco after building them in the normal riveted manner with brass sheet and angle. The thinned epoxy was run round as an alternative to soft solder, penetrating all the joints and crevices. I also think that around that time epoxy was even suggested as a means of sealing screwed boiler stays although I don’t know if heating was suggested nor how successful that might have been in the long term.

[Robert Atkinson 2Participant @robertatkinson2]

There is published data for curing various Araldite epoxies up to 100 to get it deg. C. e.g. https://www.intertronics.co.uk/wp-content/uploads/2015/12/ara2014-1.pdf

I’ve found 50 deg is fine for consumer slow cure Araldite to make it thin and / or cure quickly.

Robert.

[Michael GilliganParticipant @michaelgilligan61133]

Just to add a bit of Epoxy trivia … Canoeists seem to get away with some rather extreme ‘warming’ techniques when making emergency repairs !

MichaelG.

[Ian P]

On Ian P Said:

On Robert Atkinson 2 Said:

Basically DIY JB Weld or Devcon

or even this,

https://uk.rs-online.com/web/p/adhesives/0850962?gb=a here

Metal Loaded Epoxy, although when cured the colour is nearer to black than grey

Ian P

After using this epoxy glue on my project, the result was better than I expected. A really strong bond

[Author]

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