The Ammco shaper uses a bull gear with helical teeth, made from "bakelite" (or fabric reinforced phenolic to use the correct term). The pinion is steel. Over time, the phenolic bull gears do wear out.
I have a buddy who bought an Ammco shaper some years ago at an estate sale. It was a shop in a barn in an isolated spot. The power was turned off in the barn, so my friend could not see the shape run under power. He asked the sellers if he could take off the belt guard and pull the drive over by hand, or open the inspection cover to check the gears and slide mechanism. The sellers were in a hurry and said buy it as it sits, no taking apart or opening anything. Since the shaper looked quite good outwardly, scraped flaking all nice and crisp, and no evidence of wear or hard use, my buddy took a chance. I believe he paid 600 bucks for the shaper. He got it home and got a horrible surprise- the bull gear was missing completely.
Apparently, the bull gear is machined from phenolic and mounts onto a steel hub. The hub, shaft and slider mechanism are all in place. Our belief is the phenolic bull gear wore out, and the deceased previous owner likely sidelined the shaper until he could get another bull gear made.
Since the bull gear has helical teeth, this is not a job done in most home machine shops. So, ten or more years has elapsed and that shaper sits in my buddy's shop. We have the pinion and took all the gear data to reverse engineer a bull gear. Getting the teeth cut for a reasonable price in proportion to what he has tied up in the rest of the machine may be what is holding him from making up a new bull gear.
We found out that the bull gear on an Ammco shaper was the weak link, likely designed as a sacrificial part. The rest of the shaper is well built, using machined steel parts or cast iron where Atlas would likely have used "Zamak" (die cast zinc).
Joe Michaels