Page:Popular Science Monthly Volume 91.djvu/480

This page needs to be proofread.


Keeping Vise Jaws Open with a Coil Spring

EVERY mechanic knows what it is to work with an old vise where the screw and nut are so badly worn that it becomes necessary to back the movable jaw farther than necessary when inserting the work. The trouble caused by this back lash can be eliminated by the spring shown in the illustra- t i o n. The spring A is in- serted between the two jaws

and kept in place by two plugs B, which are driven into holes drilled in the jaws. It is evident that, as the handle is turned back- ward, the movable jaw will follow because of the spring pressure, thus eliminating all loss of motion. There is only one objection to this; that is, it fills up the space between the jaws. When necessary the spring may be easily removed. — W. Burr Bennett.

��Popular Science Monthly

���Spring in vise jaws to hold them apart

��Making Large Fly Traps for Packing Houses

GETTING rid of flies in packing houses is one of the problems which has engaged the attention of the Bureau of Entomology in cooperation with the Bureau of Animal Industry of the Department of Agriculture. An extensive investigation of the various types of fly traps used at the establishments where Federal meat inspection is main- tained has been made. While there has been much varia- tion in the effective- ness of different types of traps, it has been found that the conical trap is most efficient. One type of mechanical trap has been found par- ticularly effective. This trap is 24 in. high, 18 in. in diameter with a cone 22 in. high, by 18 in. in diameter at the base.

The frame is constructed of four hoops. Two of these hoops 18 in. in diameter are

���A cone within a cylin- der, both of screen wire

��nailed together. They form the bottom of the frame and the other two the top. The top of the trap may be made of an ordinary barrel end, with the bevel edge trimmed off so that the head will fit closely in the hoops. A 10-in. square is cut out of the center of the top to form a door, the portions of the top being held together by 1 -in. strips placed around the opening l /2 in. from the edge, to form a jamb for the door. The door is a narrow frame covered with a screen well fitted to the trap.

The top is then nailed to the upper hoops. The outer part of the trap is formed by fastening fine mesh galvanized screen wire to the outside of the hoops. Four light strips are tacked to the hoops on the outside of the trap to act as supports between top and bottom hoops, and the

���Laying out a pattern, with an ordinary car- penter's square, for cutting the cone wire mesh

ends are allowed to project at the bottom to form legs. The cone is cut from the screen wire and may be either sewed with wire or soldered where the edges meet. The top of the cone is cut off to give an opening 1 in. in diameter. The cone is then inserted in the trap and tacked to the hoop around the base. The fly trap is now complete.

In constructing the cone it is best to cut a pattern from a piece of heavy paper. An ordinary square is placed on the ma- terial from which the pattern is cut. A distance equal to the height of the cone is laid off on one leg of the square and a distance equal to one-half the diameter of the base of the cone is laid on the other leg. A line is then drawn between the two points A — B. In order to figure the distance around the base of a cone of any given diameter, multiply the diameter by 3.1416, or 3 1/7. Cut out the pattern on the curved line from C to D and on the dotted lines from A to C and A to D.

�� �