Page:Popular Science Monthly Volume 89.djvu/776

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��Popular Science Monthly

��cannot be made immune. Watches are being constructed now witii non-magnet- ic alloys in place of steel; but the alloys are not perfectly satisfactory.

The effects of temperature are taken care of more easily. The impairment of the hair-spring function is compensated for by the construction of the balance wheel, which has a rim of fused brass and steel. Each metal re-acting in differing degree to temperature, the variance in its contraction or expan- sion under the influence of cold or hear produces a bending of the rim, formed by two half-circle arcs. These are arranged and constructed so that the variation in the balance wheel will compensate for the variation in the hair-spring.

Many have wondered what is the purpose of the little screws on the edge of the balance-wheel rim. The\- are to give the wheel the exact weight, by their adjusted arrangement, to make the proper number of revolutions and to make even more accurate the balance wheel's compensation for \'ariation in the action of the hair-spring under temperature effects. When heat weak- ens the spring, it reduces the diameter of the balance wheel to correspond exactly for compensation.

��A Combination Tool With Many Uses

A VERY hand) tool can be made from tool steel 14 in. long, 3 in. wide and ^ in. thick. The teeth in the purl ,1 can be made with a three-cornered or hall round file. A hole is drilled near the edge and the metal filed to shape as shown at B to make a bottle-opener. The hole C is used as a universal nut-

���A combination bottle-opener, nut-wrench, saw-set, screw-driver and tack-puller

wrench. Two slits are cut in the edge at J) to make a saw-set. The end E is tiled to make a tack-pulKr.

��Marking Points to Bore Holes for Dowels

DWEL joints must be exact. A good method for marking simul- taneousK' in both pieces is shown in the drawing. A piece of tin or thin sheet metal is cut to convenient size and a bit of wire inserted in the exact center and

���Marker to locate points for boring holes sim- ultaneously in dowels to make neat joints

soldered, so that a part of it will project on each side of the sheet. To locate the center of the metal, draw cross lines diagonalh' from the corners. The point where the lines cross will be the exact center.

A more elaborate marker, large enough for all work, can be made from sheet brass or copper, with lines drawn parallel to each other, beginning at each side, }^ or 3^^ inch apart. These lines should be numbered, starling with l from the out- side edge and finishing near the center. When placed on the end of a square or rectangular piece the center can be located with these lines and numbers.

Place the marker on the end of the piece; then set it in the exact place on the other piece of wood and strike it. The pin points will mark both pieces.

��Painting a Ladderless Standpipe

PAINTING a ladderless st.mdpipe pr\ed to be too great a prohiiin for sewral contractors, but it was solved by an old painter. He found out how long it would take to fill the pipe, and I hen had it emptied. He took se\eral huge timbers insitle and built a raft, after which he ordered the doors closed and the pipe tilled. H\- the time the inflowing water had borne his mil to the top, he had accomplished his pur- pose. HaKOI.D HoKlNK.

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