Brazing Cast Iron

Well for cast iron fluxes are definitely not created equal.

Unfortunately the best flux I know of apparently isn't made anymore. It's Peterson #3 and it comes in two parts which you mix together. If you ever run across any of this rare vintage let me know because I'll buy it out.

Also unfortunately I've not managed to try to many of the other cast iron fluxes so I can't give solid recommendation to any of them. Just make sure the flux says it's primarily for cast iron.

If the pulley has been grease soaked then a preheat to burn all that off is a good idea. Heat it up till it cooks most of it out. Then regrind the braze area. In this case since you're asking about building it up I'm assuming you've not got a lot of brazing experience. Thus I'd recommend making a graphite or fire brick backer to support the braze as you build it up. It takes some experience to be able to build up large amounts of brass without melting the whole thing into a puddle on the floor.

Be sure to heat the whole pulley not just the braze area. This is probably the biggest mistake beginners make when brazing cast iron. If the rest of the piece is cold then it'll pull the heat away from the braze area so fast that you'll end up overheating it trying to compensate. Use fairly large tip. Bring the whole thing up to about

500 deg and then start slowly heating up the area you want to braze. Don't rush it especially in this case since you're going to have some real thin cross sections next to some thick ones. Keep the tip well back and just slowly heat the whole area. When it starts to glow red a little get some flux on there and start brushing the rod on the thinner sections. You need to get these tinned before they overheat (which they will if you wait for the heavy section to heat up). Once you get a good flow of brass over the whole area then you can start building up. For that you'll probably want to quickly switch to a slightly smaller tip which will allow easier control of the puddle. Don't take to long changing tips though since you'll loose the preheat you just did.

Wayne Cook Shamrock, TX

I have had mixed results in the past with brazing.

Would like to hear any tips and tricks from you guys. Essentially how you would proceed to do the braze.

Seems as either I don't seem to get it hot enough or get it too hot where it won't flow or stick to the base metal.

Do you prefer fluxed braze rods or the bare rods with the canned flux? Any particular brand or type?

Thanks in advance.

Marty