There are several points to be observed. The accuracy depends upon three things. First, the slot through which the cutter passes must be tight-fitting, even at the expense of working hard. Second, the shaft C must fit tightly in the holes made for it through B and F, also the arm A must be firmly attached, the shaft being filed flat at the point of attachment. The blank wheel should be keyed on the shaft or securely fastened with a setscrew. Third, the nail N must enter the punch marks accurately. As the grinding circle is so much larger than the blank, any error here is greatly reduced in the finished wheel. Once in a punch mark the nail must not be allowed to slip until the tooth has been cut.
In practice, it will be found better, after each stroke of the handle, to give a quarter turn outward to the screw G, thus avoiding the scraping of the tool on the up stroke. The cutter can be made of any suitable steel with the cutting point ground to give whatever shape is desired for the tooth. The best shape for any particular purpose can be found by reference to a book on gears.
This cutter is adapted, of course, only to the softer metals. For experimental purposes a blank cast in type metal is excellent and will last as long probably as required. The mechanism here described will cut brass perfectly well and a gear made of this more durable metal will answer for a finished construction. Type-metal blanks commend themselves because they are so easily cast, any flame which will melt solder being sufficient, and the molds, of wood, plaster of Paris or any easily worked material, being quickly constructed.—Contributed by C. W. Nieman, New York City.
A Potato Peeler
The guard is made of a piece of wire about 1 in. shorter than the blade of an ordinary table knife. The ends of the wire are turned into a coil to resemble a coil spring with coils close together. Allow enough wire to project on one end to be flattened and pointed for an eye extractor.
Guard Made of Wire
When this device is placed on the knife, the contrivance works on the same principle as a spokeshave. The first setting peels the potato without any appreciable waste, the other setting may be as desired for cutting slices.—Contributed by H. W. Ravens, Seattle, Washington.
An Easy Way to Develop Roll Film
This is simply a different motion to the tiresome seesaw one usually employs when films are being developed. In wetting them down previous to immersion in the developer, do not keep them in the water long enough to become limp, but remove them after a few quick dips, says Camera Craft, They will then retain some of their curling tendency, so that by taking one end in one hand and gradually lowering the film into the dish of developer and then raising it out of the dish, it will be found that the film will roll and unroll quite readily, much as one would let out or wind in a reel. This method will result in quicker development, because the roll is nearly always immersed in developer. The method necessitates using only one hand, making it possible to develop a second strip at the same time with the other. The illustration shows quite clearly just how the film will behave.