Brazing fail

[Brad93]

The rods kindly donated by @500e arrived today.
Had a very quick play and interestingly the 3/16 Rods seem to play nicer for me than the 1.6mm ones.

I think I may get some new flux though, grinding up this borax cone is getting tedious!

Thats always the case. The 1/8" rods are even better to use. 1.6mm just wants to ball up because the rod is melting too quickly in the flame. No good for thick stuff

 

[GraemeVW]

Woohoo, maybe I should rename this thread brazing success!

I haven't mastered it, but I seem to have properly built up cast iron with braze, so that's a start.

I did the biggest, and therefore hardest, gear first so the next bits should be easier.
No pics as it's all snugged up staying warm.
I guess when I try and reshape the teeth I'll know for sure how well it's stuck.

Thanks to everyone for the help. This place, and it's members, is/are ace.

 

[GraemeVW]

Thats always the case. The 1/8" rods are even better to use. 1.6mm just wants to ball up because the rod is melting too quickly in the flame. No good for thick stuff

Going by what i experienced, that makes perfect sense.
I had assumed, considering my limited fire power, if be better if with thin rods. But no.

I ended up using both though, big rod to build up the bulk then little rod to fill the corners.
I found it helped to actively rub the rod onto the work, sort of scrubbing with the flux. No idea if that's normal, but it seemed to get things moving.

 

[Petros55]

Gas

TIG brazing is crap in my opinion.

I've done it, it does work, there's a few motors and a big cast iron motor adjustment mechanism out in industry still running that i've tig brazed.

The problem with tig brazing is:

1.) you'll always get localised hardening of the cast iron, tig just doesn't put enough heat in to stop the cast iron chilling too fast.
This makes cracking more likely, also makes filing to shape or machining a nightmare.

2.) Even if you're really careful, when you grind or file back, you may see little silver round spots in your braze metal, that's molten cast iron that's solidified in the puddle.
Not good.

3.) Tig braze doesn't flow into the joint and out of the backside. Meaning you have to do it from both sides.
Gas brazing works properly whereby you get some degree of capillary flow.

Since you have a Superjet system the best method would be use that and Nitec 10224 powder. It is a no brainer for cast iron repairs as long as you can get sufficient heat in.