Зображення сторінки
PDF
ePub

Fourteenth: Now, pour sealing compound around the edge of the top cover, until it reaches the top of top cover; then when the sealing compound has cooled, take a putty knife and scoop extra sealing compound off of top cover, making a smooth surface over all the top of the battery.

Fifteenth: In burning the top connector to terminal post, proceed as follows: Scrape the hole of the top connector until the surface is bright and clean; scrape terminal post until top and edge are bright and clean. Now, scrape a piece of lead-preferably a small bar—bright and clean; then apply hydrogen gas flame, mixed with air under pressure, to the top connector and terminal post assembled, at the same time heating lead bar. When top connector and terminal post begin to melt, apply lead bar directly on same, melting it, thus making a firm burned connection. Then fill rest of hole-space with melted lead and smooth off even with top of top connector.

Care of Grinding Wheels.-Chattering and waviness in appearance of the part finished is usually caused either by the wheel spindle being loose in its bearings, the grinding wheel being out of true or out of balance, or particles of the material being ground having become embedded in the wheel. A loose spindle should, of course, have its bearings adjusted. In a great majority of cases, however, the cause of imperfect work is due to the wheel getting out of shape. It is important that its face should be perfectly parallel with the travel of the carriage, and in order to produce a result of this kind a diamond tool must be used, as near to the headstock or footstock center as is practicable, especially on work of small diameter. Where the work is not so small, say 2 inches in diameter, the truing device can be clamped at the most convenient point, and in either case it should be carefully seen to that the stud holding the diamond and the arm supporting same, are solid against the work. If the truing device is not rigid the face of the wheel will not be dressed perfectly true.

It will be observed that the stud in which the diamond is mounted can be revolved in its holder and it is important that the point presented to the wheel should be sharp; for instance, if the diamond should become worn and flattened, it should be turned

and thus present a new point to the wheel. Keeping the wheel true is important for the operator to observe, particularly so when he comes to make a final finish. The wheel should be traversed by the diamond at a uniform speed, rather slowly in order to give it time to cut away the particles. If it is desired to do rapid cutting, it will be found proper to pass the wheel by the diamond more rapidly thus making a rougher face on the wheel.

The number of times that the face of a grinding wheel has to be trued depends entirely on the character of the work being finished and the kind of wheel used. There are some wheels that wear away rapidly enough so that little truing is necessary. There are also cases where a harder wheel is desirable and a hard wheel necessarily requires more truing than a soft one. Where pieces are rather large and considerable stock has to be removed, it may be necessary to true the wheel each time a piece receives its finishing cut. Where the stock to be removed is not more than 164-inch diameter it is advisable to finish in one operation, but when there is as much as 137-inch diameter to be removed it is good practice to grind it in two operations. As stated above, it is desirable generally to present a sharp point of the diamond to the wheel in truing, but there are times when the smooth surface is preferable, particularly when it comes to producing a very fine finish; the flat surface of the diamond will tend somewhat to glaze the wheel and thus produce a better finish. A coarse wheel properly trued will produce a good finish.

The amount of wear the wheel is subjected to depends upon the operator in many cases. Never bring an emery, corborundum or other abrasive wheel suddenly against the work or the work abruptly to the wheel., The feed should be gradual, so that the sparking will start almost imperceptibly. Grinding is not intended to be a roughing process but is a method of finishing in most cases so careful manipulation of the feed control is required to prevent the wheel from “digging" in.

Speed for Wheels.- The table below designates number of revolutions per minute for specified diameters of wheels, to cause them to run at the respective periphery rates of 4,000, 5,000 and 6,000 feet per minute.

[blocks in formation]

The medium of 5,000 feet is usually employed in ordinary work, but in specific cases it is sometimes desirable to run them at a lower or higher rate according to requirements. We recommend a number of revolutions equivalent to a surface speed of 5,500 feet. This does not indicate that they cannot be run at a higher or lower speed, but that it is a good average speed to produce good results. To allow an ample margin of safety it is recommended that wheels should not be run at a surface speed exceeding 6,000 feet. Every shop should have a speed indicator in order that the speed of its grinding machinery may be known.

Grading of Landis Grinding Wheels.

NUMBERS

The grains are numbered according to the number of meshes per lineal inch of the sieve through which they have passed. For example, No. 30 is a grain that will pass through a sieve having . thirty meshes to the inch, but will not pass through a sieve having

thirty-six meshes. The fineness, or number, of the emery or corundum used in making a wheel determines the “number" of the wheel.

The grains (and similarly the wheels) are numbered as follows: 10, 12, 16, 20, 24, 30, 36, 46, 54, 60, 70, 80, 90, 100, 120, 150. In this list the lower numbers indicate the coarser grains, the higher numbers, the finer ones.

When ordering wheels, be sure to specify diameter, shape, thickness, size of center holes, the grade and grain or description of material to be ground and speed proposed to run the wheels. If possible, give shape number.

For grinding hardened steel and cast-iron, wheels made by what is known as the silicate process give very good results, but the vitrified wheel in our experience is the better for general use.

A soft wheel is less apt to change the temperature of the work or become glazed.

A wheel is most efficient when just soft enough not to glaze and hard enough not to wear away rapidly.

Use a fine grained wheel for finish, a coarse wheel to remove stock. For general grinding a 24 combination grain wheel gives excellent results.

A good practice is to have several grades of wheels on hand best adapted for your different classes of work.

Always keep a spare wheel or two on hand for emergencies.

[merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][ocr errors][merged small][merged small][merged small][merged small]

CHAPTER XII

USEFUL INFORMATION FOR AUTO REPAIRMEN.

Anti-Freezing Cooling Solutions—Substances Usually Combined with Water

Advantages of Different Solutions—Electrolytic Action Not Desirable The Best Mixture-Extinguishing Fires in Volatile Liquids—First Aid to the Injured—Schaefer Method of Artificial Respiration—The Repair Shop Medicine Chest—Remedy for Burns, Cuts and Abrasions-Wounds and Painful Injuries-Home-made Aseptic Gauze.

Anti-Freezing Cooling Mediums.-To lower the freezing point of water it is possible to add various substances and the proportions added determine the point at which the solution will congeal. Among the materials commonly used may be mentioned common salt, alcohol, glycerine and calcium chloride. The alkaline solutions produce a distinct electrical action wherever two dissimilar metals are used together in the cooling system, such as the brass tubing of a radiator and the solder used at the joints; the cast iron water jacket and the aluminum or brass plates used to close the core print holes; the aluminum pump casing and steel or bronze impeller, and at many other points which will vary with the design of the car and the materials of the components. The alcohol solutions evaporate very quickly, the glycerine solution affects the rubber hose, and the salt solutions leave an incrustation as the water evaporates. It is reasonable to expect electrolytic action when metals of different potential are used together in any alkaline solution, which are electrolytes of high value. Taking it all in all, the selection of the best solution involves a consideration of many facts and various requirements must be considered in the selection of that most suitable. Considering the qualities of such a corrpound it will be seen that no one will combine all the desirable

« НазадПродовжити »