gear repair question

"ben carter" wrote: (clip) Is it worth trying to braze/weld/? (clip) ^^^^^^^^^^^^^ I once repaired a couple of teeth on a cast iron printing press gear by brazing and filing. My intent was to get the press running long enough to get a new gear from the manufacturer. When the new gear arrived, the repaired one was still working, so we left it in, and, as far as I know, it is still in use.
I did it by building up the missing teeth with braze rod, and then filing to the best contour I could. I rolled the repaired gear in mesh against a good gear, and filed until it didn't feel "lumpy."

It certainly would be worth trying to me. If the brazing didn't hold up I'd try drilling two holes where the tooth was and pressing in dowel pins to act as a replacement for the tooth.
You might get some more answers in rec.crafts.metalworking.

"Artemia Salina" wrote: (clip) If the brazing didn't hold up I'd try drilling two holes where the tooth was and pressing in dowel pins to act as a replacement for the tooth. (clip) ^^^^^^^^^^^^^^^ Or a combination of the two techniques--insert steel dowels for strength, then braze and file for shape.

I had a similar problem once and wrote up my solution: GWE
ben carter wrote:

that size gear should be available at any bearing supply house for about 60 bucks if it is standard spur gear , i may need to be bored and keyed but browning makes a lot of standard gears

Talk to a gear stockist and buy either a new gear, or more likely a pair of gears. Even if you have to machine the centres out to fit the shafts, this is just easy turning work.
Repairing broken gear teeth is also a standard technique. It's also most never done by welding, vertainly not pad welding. It's impractical to shape the teeth afterwards (unless you have a gear cutting machine, in which case you just make a new pinion anyway).
Usually a new tooth (or teeth) are made on the bench, by hand filing from a new piece of steel. Things like lead or silicone rubber templates moulded over the old teeth are helpful to get the profile right. Then you fit the new teeth into a socket cut into the old pinion - sometime square, sometimes dovetailed. A pair of pins are drilled and pinned into place on the sides of this socket, so as to hold the new patch in place.

| | > Hi all | > | > I have an old Niagara 48" slip roll that has a broken tooth on one of its | > idler gears. The gear is ~3.5" dia and ~1.5" thick, One tooth broke off | > completely and pretty cleanly but with that rough cast grain inside. Is it | > worth trying to braze/weld/? it back on or should I just fork over the $400 | > to have one made? | | It certainly would be worth trying to me. If the brazing didn't hold up | I'd try drilling two holes where the tooth was and pressing in dowel pins | to act as a replacement for the tooth. | | You might get some more answers in rec.crafts.metalworking.
Since he has the tooth, and for the sake of my curiosity, can it be brazed back into place, and will the bronze wick up into the joint? If the broken parts were whetted with filler, could they be stuck back together when both sides are molten? Will the bronze raise the gear? The reason I ask it that it seems that to my uninitiated mentality that bronze wicked in by capillary action ought to have almost as much strength as the original part

Conventional brazing alloys will not wick into narrow gaps much less than 1/16 The bronze is close in strength to cast iron anyway and easily shaped. Randy

together mentality that I have a cast iron end gear on a roller shutter on my workshop that was smashed into four pieces by the bozo's who delivered it (it was second hand). I had it nickel welded - (the guy used arc with pre-heat and also peaned the welds as it cooled) and it's been ok for 15 years so far !!!!
AWEM