Grain-Elerul or : See Elevators. Grain-Mills: see Milling-)lachines, Grain.
I: rate Bfliters. Steam.
1:ItIN DI NI:, EMEh1, Quedslies desired in is lecture on time sole jeet of delivered by Mr, 'I'. funk»; Pero, President of the Tanite Co.. before the Franklin I nsl Hine, ;Ind printed in the •lourmtl of The Inslilide for Nardi, 190, he sums up the necessary qualities as follows: "Such a wheel must have tenacity to withstand tho centrifugal strain generated by its revolution at the speed of from to 11 mile per min. Its ability to resist heat must be great, inasmuch as the friction of grinding rapidly raises the metal being ground to a red acid even an almost white heat. It follows, from the above facts, that the proper base for a perfect wheel should be sonic organic substance, either vegetable or animal." Experiments with Emery- Wheels.—Mr. Paret, in the lecture above referred to, says : "To obtain the maximum result from any emery-wheel, it must be perfectly round, perfectly cen tered, must be run at a high rate of speed, and be so solidly mounted and so free from ad hering metal as to allow of continuous contact between work and wheel. With equal speed and proportional pressure a wheel 6 in. thick ought to cut off six times as much metal from a bar 6 in. wide as a wheel 1 in. thick would from a 1-in, bar.
"Experiments were made with only one make of wheel, the size being about 14 X 11 in. In comparing the cost of various processes, the same rate for labor was charged against wheel, file, and cold chisel. Charging a moderate price for the wheel (33* per cent discount from list), the maximum cost of grinding off 1 lb. of east iron was 11.6 cents. Charging a low price (60 per cent discount from list). the minimum cost was cents. The cost per lb. of filing off cast iron was 35.9 cents. In one half hour's steady work the emery-wheel removed 17 lbs. of brass. the cold chisel 1 lb. 4i ozs., and the file only 8 ozs. The wheel removed 7 lbs. 12 ozs. of cast iron, the cold chisel 2 lbs. 51 ozs., and the file only 5/ ozs. The wheel removed 2 lbs. 8 ozs. of wrought iron, the cold chisel 10i ozs., and the file 2/- ozs. The wheel removed 3 lbs.
ozs. of saw-steel, tile cold chisel 14- oz., and the file only 1 oz. The soft metal (brass) clogged the file and reduced its cut, so that the wheel removed 34 times as much as the file did. The hard saw-steel resisted the file so that the wheel removed 55 times as much as the file did. Cast iron, which neither clogged much nor resisted greatly, gave the file greater play, and the wheel only removed about 21 times as much as the file. In all these experi ments the work was forced against the wheel by hand, and such experiments gave but uncer tain results, owing to the inequality of pressure and to the personal factor. Fatigue, strength,
skill, prejudice—all might affect the results.
"Every wheel which tends to glaze badly with metal is dangerous as compared with one which does not glaze. Every free-wearing wheel is comparatively safe. lie who wants safe wheels should avoid all that glaze quickly. He should use large flanges with very thin wheels. He should have mandrel-holes of moderate size and very slightly larger than the spindle. He should mount the wheels substantially. And still, to be absolutely safe, he may add coverings and guards, provided these are not of cast iron, but are of wrought iron, boiler plate, or tough steel. Another established point is that, as a general rule, increased wear of wheel indicates increased product in the amount of metal ground. It is a nice point (yet to be decided by the invention and long use of a competent test machine) just how far wheel consumption and metal removal are proportionate. The careful observations thus far made seem to indicate that there is a reasonable average maximum removal of metal compatible with economical consumption of wheel material ; that if, by increased speed or pressure, the wheel is made to wear out faster than this, more metal can be removed, but that the gain in metal removal is far more than balanced by the increased loss of wheel material." Conaptitwe Trials of Em ery-11Thcels.—A commission of experts, consisting of Dr. Cole man Sellers, Prof. J. E. Denton, and Alfred H. Wolff. in 1889 and 1890, made, oh behalf of the Tanite Co., an extensive investigation into the relative merits of the emery-wheels made by fifteen different manufacturers in the United States. From the preliminary report of this commission, made in 1891, it appears that of the fifteen varieties six were found too unsafe to warrant their general use, 57 per cent of the wheels bursting under the same conditions which other wheels pressed through uninjured. Eleven varieties (among which are included the six unsafe varieties) were found to be such slow emitters that the average metal removal of ten of them was less than the general average of all the wheels. Of the fifteen varieties, only four were found to be rapid cutters. Of these, one wore so rapidly that the cost of its rapid cut was unreasonable. This left three safe, effective, and satisfactory wheels, one of which, how ever, was demonstrated to work at a greater cost than the others. The rivalry was thus nar rowed to two wheels, but, in the judgment of the board, further trials are still necessary be fore the relative values can be determined.