948 



Popular Science Monthly 



How to make a Secure Joint 

 in Copper Tubing 



^INCE copper tubing is so useful in 

 O radio work, knowledge of how to make 

 a neat and ef- 

 fective joint 

 should be valu- 

 able. In build- 

 ing helices • or 

 spirals it is im- 

 possible to 

 splice short 

 pieces in the or- 

 dinary way. By 

 tapping threads 

 inside each of 

 the abutting ends and inserting a short 

 threaded piece of copper or brass rod to 

 fit, as in Fig. i;* a perfect joint may be 

 made. Where a wire extension from the 

 end of the tube is desired, the same general 

 plan may be followed, as shown in Fig. 2 of 

 the illustration. — F. Mac Murphy. 



A threaded plug in the 

 pipe ends for a close joint 



Things to Know About Lubricants 

 for Machinery 



ALL machinery owners have had it 

 drummed into them that only a good 

 grade of mineral oil is fit for oiling their 

 machinery; but there are a few extreme 

 cases in which something else is used, and 

 they are interesting enough to mention. 

 The function of a lubricant is to supply a 

 thin film between the sliding metal parts 

 so that they do not touch each other with 

 sufficient pressure to produce friction or 

 heat or to cut one into the other, and to 

 keep the sliding parts cool. 



The "bearing pressure," or pressure of 

 one part upon the other, determines to a 

 great extent the kind or quality of lubricat- 

 ing oil to use; for with heavy pressure a 

 poor or thin oil will squeeze out, or its film 

 become broken down. Then the metal 

 parts will rub and heating and cutting will 

 begin, to the detriment of the machinery. 



As a cooling medium, water will be found 

 satisfactory. Where pressures are light and 

 a flood or bath of water can be maintained 

 without causing rusting, water is fully as 

 satisfactory as oil and much cheaper, al- 

 though the instances where it may be used 

 are not many. 



The garage man finds a great deal of 

 trouble caused by carbon in the cylinders — 

 pre-ignition, knocking, loss of power, etc. 

 This carbon is considered a necessary evil, 



of no good whatever. But experience shows 

 that a certain quantity of this carbon — not 

 an excess — is as good a lubricant as may 

 be found. For sleeve-valve motors it has 

 been found that if a carbon deposit is in 

 the grooves and creases of the sleeves no 

 other lubrication is needed. This is easy 

 to believe when we know that carbon is a 

 constituent of mineral oil. Such a deposit 

 is a form of graphite, which we know is 

 self lubricating. Therefore it is a substitute 

 for grease. 



I Pure glycerine is as good a lubricant as 

 any oil if used where there . is no great 

 amount of heat. It will stand almost any 

 ordinary bearing pressure and has a high 

 viscosity rating. In plants manufacturing 

 food products, bottling plants and brew- 

 eries, compressed air is used extensively in 

 contact with the products for various pur- 

 poses, such as charging, filling, etc., and 

 there is always a certain amount of the 

 lubricant from the cylinder of the air- 

 compressor that finds its way through the 

 pipes and comes in contact with the prod- 

 uct. In almost all cases this would be dis- 

 astrous if ordinary lubricating oil were 

 used, owing to the discoloring, the various 

 chemical actions and the possible injury to 

 health. But for this purpose glycerine is 

 extensively used. 



Fish oils, vegetable oils, animal oils and 

 sometimes kerosene are used for such 

 machinery. We find the various vegetable 

 oils used on machinery in the preparation 

 of products where a single drop of mineral 

 oil on, or in, the product would be decidedly 

 harmful. 



Thus, for instance, a machine working on 

 corn products is lubricated with corn oil 

 and the operator is supplied with a squirt 

 can filled with this oil. None of the vege- 

 table or animal oils, however, is to be rec- 

 ommended for lubricating any metal sur- 

 face. They are for use only in extreme 

 cases where the bearing pressure is low. 

 The bearings should be carefully attended 

 to and watched. 



A mixture of lard oil and kerosene will 

 make a sufficiently free-running journal 

 and is often used on hand-operated feed 

 tables of machines. When freshly applied 

 it gives a free and easy sliding fit to roller- 

 bearings, but owing to the evaporation of 

 the kerosene and the gumming quality of 

 the lard oil, it must be renewed and fresh- 

 ened up frequently. Soap is the best lubri- 

 cant to use on wood, and soapy water makes 

 the best lubricant for rubber surfaces. 



