Thread: cracked casting... best plan of attack

Started working on my 6" jointer and noticed this crack.
it is on the gib side of the infeed table and extends 45mm.
It will have to be clamped somehow , but what is the best fix.. brazing, welding ..etc
ken.

Hi Kenny,
Without question if you are dealing with cast iron, the best repair is to braze the repair.

The advantage is that you will have a strong repair and it is quicker to perform than the other forms of welding repair.
It entails vee ing out the crack and filling it with braze material.

If you don't have the gear to braze I would advise having a welding /engineering shop do it for you.

If you are going to have a go your self be prepared to hire an oxy acetylene set- a small one will suffice as I personally don't believe the average LP / butane torch has the caloriic value to give the required result.

Use
Nickel Bronze 2.4mm and a pot of suitable flux.

Grahame

G'day Ken,
Before you braze the crack, locate the furthest point to which it has extended and drill a small hole (2mm) through it. This will prevent it from continuing to creep along the rest of the casting.

A good way to locate the end of the crack is to spray paint a light coat of etch primer where you think the end is, mix a few drops of dark food dye in some metho and drip it onto the crack. The crack will wick the coloured metho along it's length and the etch primer will provide contrast making it easier to identify the end. Sort of a DIY Flawchek substitute.
Cheers,
Greg.

If you have access to suitable gear, then I quite like a nickel based stick welding electrode (castcraft 55 or equivalent) with the flux knocked off then used a filler rod for TIG welding. This method has become my favourite repair method for smaller castings lately.
Another sweet, though expensive method I love is Eutectic Xuper 2240 stick electrodes. https://www.castolin.com/en-US/produ...ode-xuper-2240 They are a perfect colour match, run well and machine well, leaving a repair that is indistinguishable from the virgin casting.

Hi Guys,

Being old school, I do wonder how much distortion is introduced with the localised heating from Tig/mig welding of cast iron.

Anyway ken, that is a nasty place to get a crack, right on the edge of that dovetail !

Admit to not having a clue when it comes to this type of repair, but when reading about casting repair theads in the past, pre/post heating of the part seems to come up a lot.

Hi Jatt, Guys,

Originally Posted by jatt

Admit to not having a clue when it comes to this type of repair, but when reading about casting repair theads in the past, pre/post heating of the part seems to come up a lot.

I haven't done any cast iron welding for nearly 50 years ! In my day welding cast iron was very much a specialised job done with the work heated up to just about a dull red colour then welded using cast iron rods and oxyacetylene gear.

Originally Posted by BaronJ

Hi Guys,

Being old school, I do wonder how much distortion is introduced with the localised heating from Tig/mig welding of cast iron.

Anyway ken, that is a nasty place to get a crack, right on the edge of that dovetail !

As you have quite rightly identified, distortion is your enemy when it comes to cast iron repairs, particularly when dealing with parts that are under some form of restraint (like the hub of a spoked wheel for example). I haven't had too many issues with distortion caused by TIG welding and in fact I would say that it is less prone to distortion than stick welding and braze welding in many instances. If I was concerned, peening between beads and a good preheat would suffice to control most issues. I find that the intense arc of the TIG process allows one to run a bead that fuses impeccably without lingering too long and causing heat build up sufficient to give trouble.
Having said that, equally good work can be done by someone who knows their game using oxy acetylene or a stick welder.

We are talking tig yet we are unaware of what tools the OP has and that's only IF he chooses to pursue the repair himself.

I have repaired cast iron over my 50 plus years in the trade.I spent the first two years doing no other repairs than cast iron. I understand cast iron and its problems extremely well.

Since degree of difficulty and money always seem to be a factor of cast iron welding discussion,I will say this again.
For the type of repair involved- ie prevention of crack propagation, Oxy acetylene brazing is the quickest , cheapest and most appropriate repair.

There no real tension or stress apparent. Even if the OP sends the work out a general welding shop will handle this easy and quickly.
However if the op has some oxy experience it offer the most successful outcome. No distortion and no cracking guaranteed.

The damage is on the end and corner of the unit.
Grind it out and flux it and fill it. It is a 30 to 40 minute job. There's no compelling reason to use an alternate procedure.
If kenny10 wants to go this way I am more than happy to write out the entire procedure.

Grahame

I assume you are referring to my post Grahame. My opening words were "if you have access to suitable equipment". I then answered BaronJ's very reasonable question regarding distortion relating to newer welding processes.
It is not at all uncommon to find people with access to a simple lift arc TIG. but no oxy set.
I have noticed that fewer and fewer engineering workshops are keeping brazing consumables in their arsenal, probably due to the cost of consumables and gas, which is a shame as braze welding is still a very viable process.
Ultimately, unless the OP performs the job himself or with a mate, it will be up to the chosen workshop as to how they perform the repair.

I have noticed that fewer and fewer engineering workshops are keeping brazing consumables in their arsenal, probably due to the cost of consumables and gas

You don't need to be a "engineering shop" to take a hard look at your spend on the above. After having for several years the Oxy got the flick for this very reason, not to mention lack of use. Shame cause there are times when its real handy to have.

Thanks guys.. unfortunately I don't have access to any suitable equipment, so I will be sending it out to be done. The crack may have been there for some time as I found two offcuts of shim material on the opposite dovetail, possibly to counter the crack.
My first thought was to drill and tap for one or two 6mm screws.. its wide enough at the crack, being 11mm. What are your thoughts on this ?
Ken.

Originally Posted by Grahame Collins

We are talking tig yet we are unaware of what tools the OP has and that's only IF he chooses to pursue the repair himself.

I have repaired cast iron over my 50 plus years in the trade.I spent the first two years doing no other repairs than cast iron. I understand cast iron and its problems extremely well.

Grind it out and flux it and fill it. It is a 30 to 40 minute job. There's no compelling reason to use an alternate procedure.
If kenny10 wants to go this way I am more than happy to write out the entire procedure.

Grahame

I totally agree with Grahame on this. Braze it. You are unlikely to get distortion from shrinkage with brazing and should get 100% bond coverage if done correctly.


Just be aware that bronze filler achieves it's maximum strength at the minimum fill thickness. So only take out the bare minimum when prepping the job.

There are several rods that would do the job, but always buy good quality - BOC rods always get the nod from me.

Unfortunately everyone seems to be MIG and TIG happy these days and gas torches get looked down on as "old hat" by people who I suspect have never used one.

Cheers Rob

If you want to have a go at tapping and screwing back together I can't really see a problem.

"... tap for one or two 6mm screws."

Thats what I would do. Three 5mm csk socket heads. Clamp it while drilling and tapping so swarf doesnt wedge the crack open. Small holes so you can weld or braze it later if needed.