Anybody know of a cheap source...

Lots of components like this are manufactured in the way they are because it is the cheapest manufacturing method in some given situation. Pressing an internally splined gear on a splined shaft is faster than machining the gear and shaft to the tolerances needed for an interference fit nor does it require any brazing or welding of what is probably a cast iron gear to a cold-rolled steel shaft. But that does not mean that you have to repair it in exactly the same way.

A machine shop that has a milling machine can mill a new gear. Easiest is they have a horizontal mill rather than a vertical mill like a Bridgeport. They need a dividing head and they need a set of gear cutters of that pitch.

I'll bet that the gear is a pressed / shrunk interference fit on that shaft. I doubt that a part like that was machined "from the solid". They probably machined the shaft itself and then pressed or shrank the gear onto it. If you measure around the gear and tell me the number of teeth, I can look up what pitch gear it is. You can get a lot of stock spur gears like that from places that sell power train components. Boston Gear and Martin are two brand names for stock gears.

If you have a oxy-LP or oxy-acetylene heating torch and a hydraulic press I'd try heating the broken gear, keeping the heat as much as possible toward the outside of the gear and off the shaft itself. When you get the outside starting to glow a bit support the gear well in the bed of the press and press on the center of the shaft. If it isn't a press fit you are not going to harm it and if it is, I'll bet the gear will come off and it will be a stock item that you can get at an industrial supply house.

You don't have a lot to lose playing around with the broken part and I think there are a number of ways you can rebuild the part you have. If you give me the specs on the gear, distance around the outside of the teeth, diameter, number of teeth and width of the face of the teeth (or thickness of the gear if it has a uniform thickness) I'll look in my gear company catalogs and tell you if it is close to stock. If you can measure the thickness of the shaft immediately beside the gear part.

Even if the component was made in one piece by machining from one solid billet of metal, that does not mean that you cannot put it in a lathe, cut the gear off (just turn the gear down) to the diameter of the rest of the shaf and then press a standard gear on in place of this one. If you are a good machinist you can make it a press fit and if you cannot get the tolerance just right, you can slip the new gear on and then braze it or even stick it a few places with a wire-feed welder.

It all depends on whether it is a stock-type gear or not, but if it is you have several options.

I have a lathe and could turn it down for you. I live in St. Paul MN. But you probably have a machine shop in your area that can do it just as well and can advise you on other ways to fix this.

Ed Lotterman
St. Paul MN