An Inexpensive Electric Cork Boring Machine Robert Barnard, Montana State College, Bozernan
A Fast, Easy Method for the Preparation of Cross Hairs Jerry W. Ellis
A low cost electric cork boring machine can he made from a '/,in. household-type drill and stand. The only modification to t,he drill stand is a small mercury switch installed on the handle so that when t h e h a n d l e is pulled down the drill will s t a r t a u t o m a t i cally. The det,ails of a cork borer designed to bore cork and rubber st,oppers to ac,cammodate 6-mm tubing is showu in the diagram. The borer was machined out of mild steel. The opening in the side of the cutter makes this a selfcleaning device. Borers of various sizes can be made. A suggested modification is that the bevel of the cutter be reversed so that it is on the iuside of the tube. ~
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Kansas State College of Pittsburg
Due to the fragility of the cross hairs in telescopes and other instruments, they are sometimes broken or destroyed, and in many cases this renders the instrument useless. Repairing these broken hairs or making new ones presents somewhat of a problem. An answer to the problem lies in a tube of plastic cement such as is used in the construction of model airplanes (Amco was used in this case) and a long pointed object such as a piece of stiff wire or a long thin nail. The hairs are made by putting a small amount of fresh glue on the pointed end of the object and quickly touching it to the frame and then again to the opposite side. Another one may be placed a t right angles if desired, and this is probably the most difficult part of the entire operation. The hairs are literally generated from the glue, much like capillary tubes are pulled from glass tubing. The speed with which the operation is done is the critical factor. Since the d u e solvent evavorates quickly and leaves a stiff cover over any exposed area of the glue, parts of this cover are pulled into the hair when it is generated. This results in a general non-uniformity of the hair diameter. If the operatiou is done too slowly, the hair will either not form, or will break before completion. When newly-formed hairs dry, they become taut and straight even if they were not taut when formed. The technique required for production of suitable hairs may be acquired in a few minutes. ~
334
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Journal of Chemicol Education
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