Workbench Creations

My snow blower broke; it is an old machine, but has worked great for many years. The problem is that the front auger stopped spinning because a sprocket got loose and worn-down by the chain. Getting a new sprocket from the snow blower manufacturer didn't seem possible, as the machine is very old and the sprocket is welded onto the shaft. I decided that instead of scrapping the machine, which has an engine that runs great, I would see if I could make my own sprocket from some scrap metal.

My first thought was to look online to see if anyone had directions on how to make a sprocket, but I found nothing. My second thought was to cut a round blank on the lathe, put it on a rotary table on a milling machine, and cut each tooth. However, this seemed like a lot of work. My third thought on how to do this was to start with metal larger than the sprocket, drill holes for each tooth and the center, and then cut away until I got to the holes. This method seemed easier and is what I went with.

I started by measuring the chain pitch and the diameter of one chain link that meshes with the sprocket. I also looked at my old mangled sprocket and counted the number of teeth on it. Multiplying the number of teeth by the chain pitch gives you a circumference – and with a little math, a radius of a circle to draw. I had a friend make a template on a computer with my dimensions; I printed the template out and taped it to my metal scrap.

Using a center punch, I marked the center and all the points where the spokes intersect the circle. I carefully drilled out all these points on a drill press, using a drill bit that was matched to the diameter of the chain link part. I found it useful to drill the center hole first, mount the part on the lathe, and cut a small circle grove to make sure everything was centered.

With all the holes drilled, I cut off as much excess metal as I could and then mounted the part on the lathe. On the lathe, I cut the part until it was round and then started cutting into all the holes I drilled for the teeth. I'd imagine that with a lot of patience and no lathe someone could do this with a bench grinder, although it might not be as accurate.

Now that the part was beginning to look like a sprocket, I took a hand grinder and cut away the little excess metal on the top of each tooth. I also used the hand grinder to round off some of the sharp parts and then tried meshing it with the chain; it was a perfect fit.