This paper gives the results of a series of drilling tests on nine different metals using eleven different cutting fluids. Modern twist drills having 30-deg helices, ranging from ½ in. to 1½ in. in diameter, were used. The materials consisted of a cast aluminum alloy, free-cutting brass, cast iron, malleable cast iron, S.A.E. 1020 steel, S.A.E. 1035 steel, carbon tool steel, S.A.E. 3150 steel, and S.A.E. 1112 steel. The eleven cutting fluids consisted of dry cutting, borax water, two soluble oils, lard oil, two straight mineral oils, two compounded oils, and two sulphurized oils.

For each material a formula for torque and thrust was developed as a function of variable diameter and variable feed. Constants for these formulas for dry cutting and each of the eleven cutting fluids are determined. The influence of the different cutting fluids on each metal is shown. With the net output power for drilling dry expressed as 100 per cent, the savings made are as follows:

33.3 per cent for S.A.E. 1020 steel when using a sulphurized oil

31.7 per cent for aluminum alloy when using a 90 per cent mineral-10 per cent lard oil

26.0 per cent for S.A.E. 1035 steel when using a sulphurized lard-mineral oil

23.0 per cent for S.A.E. 3150 steel when using a sulphurized mineral oil

21.0 per cent for carbon tool steel when using sulphurized mineral oil

17.2 per cent for cast iron when using a mineral oil containing 5 per cent oleic acid

10.5 per cent for malleable cast iron when using any kind of an oil, such as lard, mineral, compounded, or sulphurized

6.8 per cent for S.A.E. 1112 steel when using a sulphurized lard-mineral oil.

No appreciable difference is made whether free-cutting brass is cut dry or with any kind of a cutting fluid.

In the development of the formulas for torque and thrust, it was found that the same results of the exponents for drill diameter and feed would be obtained regardless of the diameter of the drill used in the variable feed tests and regardless of the feed used in the variable drill diameter tests. The values of these exponents are not influenced by the type of cutting fluid used. The torque and thrust lines as a function of feed or diameter as the variable are merely displaced vertically, if affected at all. The constants of the torque and thrust formulas, however, indicate the cutting characteristics of the cutting fluids.

The torque and thrust formulas for all kinds of steels as covered in the paper are found to be identical except for different values of the constant. Other metals, however, produce formulas apparently characteristic of that metal. In other words, different formulas as summarized in Table 4 are developed for the aluminum alloy, the free-cutting brass, cast iron, malleable iron, and steel.

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