Helical Gear Cutting On Milling Machine

Helical Gear-

Unlike Spur gears, Helical gears and Helical Gearbox both have the capacity to conduct a smooth operation. The teeth on a helical gear cut at an angle to the face of the gear. So, during the process when two of the teeth start to engage, the contact is gradual- starting at one end of the tooth and maintaining contact as the gear rotates into full engagement. When it comes to transmissions, helical is the most commonly used gears and it even generates large amounts of thrust.

AIM:

To make a helical gear from a CI blank using milling machine MATERIAL REQUIRED : Cast iron blank of Ф50 mm

TOOLS REQUIRED :

1. Turning tool 2. Milling cutter ( 2 mm module ) 3. Vernier caliper ( 0- 150 mm) 4. Drilling tool Ф 10 mm ,Ф20 mm 5. Mandrel Ф 20 mm 6. Spanner 7. Gear tooth Vernier

FORMULA : Outer diameter = (N+2) M, Module =OD/ (N+2), No .of teeth = (OD/M) -2 N- Number of teeth M=module OD= outer diameter

PROCEDURE OF HELICAL GEAR CUTTING : 1. Turn the given CI bank to required diameter in centre lathe. 2. Drill a hole in the blank of diameter equal to mandrel size. 3. Fix the blank between two centers of the dividing head using mandrel. 4. Set the milling cutter on the machine spindle and select the suitable speed. 5. Raise the table (knee) vertically up until blank touches the cutter. 6. Calculate depth of cut and indexing calculation from module & number of teeth. 7. Give the depth of cut by raising the knee up. 8. According to index calculation set the dividing head. 9. Switch on the spindle and feed the blank against the rotating cutter by reciprocating the table 10. Move the index arm on the index plate according to the calculated number of holes. 11. Feed the blank against the rotating cutter to cut the next tooth. 12. Repeat the same for remaining teeth.

MODEL CALCULATION FOR HELICAL GEAR: No of teeth(z) = 30 Module(m) = 2 mm External dia. of blank = (z+2)*m = (30+2)*2=64 Depth of cut =2.25*m = 2.25*2 = 4.5 mm The indexing crank rotation = one complete rotation and move arm holes in 33 concentric circle.