Brazing cast iron gear box

I broke the gerar box on my woods mower, from a large rock strike. The break is actually a crack in the end where the blade shaft extends through the housing. I want to braze the crack. Will it be necessary to heat the whole casting, or can I heat the end gradually where I plan to do the brazing? After the repair I plan to install a metal ring over the end, and braze it in place. Any one have a gear box laying around for a woods 6 ft mower? I should have walked away from that job, because one of my helpers also burned up one of my redmax line trimmers. I guess you win some, and lose some.Stan

Call JDR Industries, Inc. also called Farmers Choice, in Omaha, Neb. phone # 1-800-533-8935,and order some Gold Rod, it is a little expensive but it should do the job for you and you can use your arc welder. They sell good welding rod and the Gold Rod is supposed to weld almost anything. I buy rod from them quite frequently. Nice people to do business with.

Stan -

Shoot me an email. I may have a access to a gear box for you.

Brian

You need to drill a hole at the end of the crack to keep it from spreading. And yes you must warm the hole thing . It will braze nice with the correct rod.

But if another uncracked piece is around grab it.

I've used that gold rod other guy talks about it's expensive but so is cast or nickel rod now days. All 3 work good and yes you need to heat the housing and then cool it slowly pinging the weld. Welded a grain cart gear box together with nickel cast rod that pushed out on side when water got in it from a bad seal on top and it's still holding together.

Hi Stan,

Electric arc welding of any type would be a extremly poor choice for this repair.

Brazing is a process above solder temperatures but below fusion temperatures. Simpliy put, brazing is a surface smear of metal. It has it's purpose but not on this application as it's just too weak of a repair.

O/A gas welding would be the best welding process choice. Here you will want to "V" notch the crack too a point just shy of 100% of base metal thickness, and extending the "V" atleast 1/4" beyond the existing crack, then O/A gas weld using a cast iron filler rod.

When done welding, quickly peen the weld face (surface) to remove tension then bury in dry sand until cool.

Predry your sand by spreading the sand on sheet metal and let dry in the sun. Use cinder blocks to make a temperary box form, then add dry sand to the bottom, put in your repaired part, then cover with sand, cool for 24hrs. About 2" of sand on top and bottom.

Since this sounds like a high stress repair area, YMMV with ending results. A replacement gear box might be a better solution and keep one this for a quick change out for next time.

If time is money, then replace the gear box, new, period. This would be my choice on my equipment if I was making money with it.

T_Bone

Well T Bone is right.I would look hard for a used or new one.Then I would try and weld it with 7018.I just welded a cast iron pulley on a combine the other day with 7018.I veed it out,vise grip clamped a flat piece of metal on the other side,then heated with a torch kind of hot,burnt all the paint that was on it off,welded about an inch,peen,weld,peen,weld until it was finished,hit it with the torch again to where it was hot,walked away,a half hour later checked it for cracks,no cracks,no cracks the next day.

The way I told you is risky,it stands a chance of cracking,especially right beside where you weld,also in the case of your crack you need to drill a hole in the end of the crack as others said so it wont get longer.You would want to grind the top of the weld while its hot as well,I forgot to say that.When I was done with that pulley,welded in place on the combine,ground down,if you shot paint on it you wouldnt know it was there unless somebody told you.Ive done this a few times before and kind of have a feel for it.

On that case,it might be hard to hold it no matter what you weld it with.Cast iron is hard to really tell you how to weld,and very brittle.The thing is you want a good weld,dont mess around,you cant stop until you are done,and you stand a good chance it will break.T Bones method is probably the best and strongest of those mentioned here.You might want to think about taking it to a welder,but like I said to start with the best is a new or good used piece.