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Then heat the tip to a cherry red and hit it a sharp blow with a hammer to flatten it sHghtly, and quickly dip into cold water. This gives about the proper de- gree of hardness. The necessary clear- ance was given when it was flattened, and the point is then ground down until the flat side is very nearly a half-round and the narrow side tapers to a point at an angle of 30 degrees. The other end is filed off slightly on a long angle, as shown in Fig. 4. This slides up upon the slot in the chuck and prevents the drill from turning.
The bow is made of some limber wood, such as elm or hickory, and is trimmed down so that when bent it will give the desired tension to the string. This depends on the wood used and should be sufficient to keep the cord from slipping when twisted once around the spool. The bow used with the drill de- scribed was 2.y-z feet long, ^ inch wide and J4 inch thick. The cord should be of leather attached to one end and about 6 inches above the other end, which was left for a handle.
The chuck described here is expressly made for the wire drills, but if the maker has any other drills that bore with a backward and forward motion, he could use any design of chuck he wishes in order to accommodate the drills.
This bow-drill, if the points are well
��Popular Science Monthly
��ground, will quickly bore wood or iron and if supplied with turpentine will even bore glass. When needed, the drills can be made longer, but when the length is over 6 inches care must be taken or they will bend when pressure is exerted on the handle. To rotate the drill, the bow- string is twisted once around the spool and the bow is then pushed rapidly backward and forward at right angles to the handle. — Rae McGooch.
����An attractive non-upsetting ink bottle stand
��'_-- The bottle will glow with the sparks which fill it
��The Luminous Bottle
TO perform this experiment, fill a big bottle nearly full of water and run a wire from one terminal of a spark coil to the inside of the bottle. Set the bottle on a plate of glass to insulate it from the table. Then run a wire from the other terminal and tie it securely around the bottle about half way up. When the spark- gap is started, little sparks are given off from the wire to form a fine network all about the bot- tle. — F. M. Kimble.
Non-Upsetting Holder for Drawing Inks
AN ink stand that will not up- L set, owing to the broad base secured, can be made according to the dimensions given in the diagram. The base should be cut first and the sides fitted after- wards. Cigar box wood will do. The two end pieces should pro- trude in front of the bottles and the upper surfaces should be whittled out for pens.
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