TABLE OF CONTENTS BACKLASH IS THE SHORTEST DISTANCE BETWEEN NON-DRIVING TOOTH SURFACES OF ADJACENT TEETH IN MATING GEARS.
TEETH SHOULD BE CUT THINNER THAN THE THEORETICAL THICKNESS TO OBTAIN THE AMOUNT OF BACKLASH REQUIRED. IN THE MAJORITY OF CASES, THE TEETH OF BOTH MATING GEARS ARE EACH CUT THINNER BY AN AMOUNT EQUAL TO ONE-HALF THE BACKLASH REQUIRED. WHERE SMALL PINIONS ARE USED, ALL OF THE BACKLASH SHOULD BE OBTAINED BY CUTTING THE TEETH OF THE MATING GEAR THINNER BY AN AMOUNT EQUAL TO THE TOTAL BACKLASH.
THE TEETH CAN BE MADE THINNER BY CUTTING THE TEETH DEEPER.
WHEN,
B = AMOUNT OF BACKLASH, INCHES.
X = EXCESS DEPTH OF CUT TO PROVIDE BACKLASH, INCHES.
? n = NORMAL PRESSURE ANGLE OF GENERATING TOOL.
THEN,
WHEN BOTH GEARS ARE CUT DEEPER.
WHEN ONE GEAR ONLY IS CUT DEEPER
HIGH SPEED GEARS REQUIRE MORE BACKLASH THAN LOW SPEED GEARS. FOR INDUSTRIAL HELICAL AND HERRING BONE GEARS (RUNNING NOT OVER 1500 FT.PER MIN.PITCH LINE VELOCITY) THE FOLLOWING TABLE GIVES VALUES OF BACKLASH THAT SHOULD BE SATISFACTORY.
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FOR HIGH SPEED GEARS (RUNNING AT PITCH LINE VELOCITIES IN EXCESS OF 1500 FT.PER MIN.) THE BACKLASH SHOULD BE NOT LESS THAN THE FOLLOWING:
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