The main object of this manual is to provide the means to produce spur gears so that we can add change gears to the lathe. While we can hardly expect to produce a perfect involute gear tooth in the home shop, we can certainly make a set of change gears for the lathe that will mesh nicely and provide the accurate and positive drive to the lead screw that is needed for cutting screw threads on the lathe. The work is much easier than you may have imagined, and the cost is so slight that it just doesn't make sense to deny yourself the advantage of this improvement to your shop. Few of us could bear the expense of a set of formed gear tooth cutters for the miller, but it is an easy job to grind a simple fly cutter at a cost of about half a dollar. Mine has cut something over 200 gear teeth with no sign of blunting. The gears are uniform and mesh nicely with each other and with commercially made gears. There would be no problem in gathering enough data to write an entire volume on gear technology alone, but most of the information would be of little value in the home shop. Don't be concerned with the inability to produce a perfect involute gear form because such a thing hardly exists except in theory. Modern equipment can come very close to perfection but they still miss by a little bit. You can come so close with these simple methods that only an expert with very exotic equipment could find the error. A worm wheel dividing head is a simple and fascinating device. It is the only practical way to provide a broad range of dividing capability to the shop, and its versatility will amaze you. It not only enables you to make accurate gears, but it will handle any other dividing or indexing chore that you may assign to it. Its accuracy will be more than adequate for the broad and general class of work, and you will have a piece of equipment that most home shop operators must do without. If you have completed any of the earlier projects in the series you won't find these projects difficult. The first chapter is largely a review of simple methods and devices from earlier manuals, and these provide what is required to build the dividing head and add change gears to the lathe. The castings that are required are all within the one quart capacity of the charcoal foundry, and the simple methods for producing the castings have been well covered in the earlier manuals. Most of our discussion will be on finishing and fitting the parts.

 

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