Cast iron repair

I would be inclined to go for one of the fancy epoxies as well as the screws etc. Do make sure tat you use the special cleaner before you apply the stuff as it transforms adhesion. I do not fancy heating things up even at braze temps as CI is a devil to braze due to carbon content. Peter

I take that to mean in/near one of the dovetails?

In that case, brazing or welding may well cause more movement than you would like and what you've done plus some low viscosity cyanoacrylate is about all you can do without major re-machining/re-scraping.

In areas that are more ameanable to post treatment machining, welding with high nickel rods works very well. I've repaired missing teeth on the feed gears of my shaper and recently re-made the working ends of the back-gear shifting fork on the milling machine with this technique.

A few years ago I got a battered drill press from the Cynical Engineer (John S.). I repaired the scars in its table with steel wire and a MIG welding set. After grinding the surface, you couldn't tell where all the scars had been. But the weld deposit on that one was so hard that only grinding would work. The nickel leaves no hard zone if you get the heat regime right.

Regards Mark Rand RTFM

Yes - the triangular dovetail itself is breaking off. I say breaking off, the crack is less than a cigarette paper wide; so there is little possibility of using solvents and pretreatments for glues.

Yes, some low-viscosity superglue might get in the crack, though I doubt an epoxy would.

The bottom bearing surface is still fine, but I am worried about the surface on the V (where the gib touches it). Thing is, there is a LOT of work in the casting, it has half a rotary table machined in it as well.

I'd just use bronze brazing, I think, if I was going to heat it. I know nickel is good, almost standard, but bronze needs less heat, it is well strong enough, and I do a lot more brazing than welding anyway.

That's if you _can_ braze cast iron - anybody know?

Thanks,

-- Peter F

Araldite makes a stronger bond than cyanoacrylate with metal and it does go very runny when heated. If you are going to warm Araldite use the slow cure one instead of the quick cure one.

Is there any possibility of diffusion bonding a cracked item back together?

Scrim

In article , Peter Fairbrother writes

Peter,

Never tried it myself, but many years ago I did get the opportunity to ask Tom Walsh (Tubal Cain) how to go about repairing a crack in a cast-iron vice, and he told me that sifbronze was specifically designed for that purpose.

Think I've remembered the name correctly, apologies if not.

PS - seems the company makes many more things than this - see:

David

Peter

Personally, I wouldn't go anywhere near cast iron with significant heat unless I was a professional and had access to a means of pre-heating and controlled cooling

Regardless of what others may have said about the unsuitability of epoxies, there ARE epoxies that are specifically formulated to be highly viscous and to penetrate and bond hairline cracks in materials such as concrete.

If in doubt, talk to Rotafix Resins, in Swansea. I have used their stuff to successfully infuse the matrix left in structural oak and elm beams after severe attack by Death Watch beetle and woodworm.

--

Chris Edwards (in deepest Dorset) "There *must* be an easier way!"

Are we talking about the BCA??

Mark Rand RTFM

Yes. It's the part on which the head goes up and down.

The crack is not really visible, it goes down from the mark along where the join between the V and the body is thin. I don't know if it was me when I cut the hole for the bearings, or if it came that way - I am fitting a ballscrew to the axis.

The bit also turns so you can drill holes at an angle - it's not really a rotary table as such, but it is a complex and accurately hand scraped rotary action nevertheless.

-- Peter Fairbrother

Epoxy won't be anything like strong enough if the area is load bearing. Have tried this on more than one occasion. Epoxy bonding to cast iron just pulls away at particle level.

Years ago, I bought a chore Horse charger with broken cast iron base and had it, iirc, bronze brazed in a local engineering shop. It's the only way to make it as strong as original. You could also perhaps fabricate a new part from steel, or apply strip steel clamp straps around the affected area...

Regards,

Chris