Ain Shams University.

Metal Cutting Machines and

Faculty of Engineering. Technology - MDP 384s.
Design and Production Eng. Dept. Spring 2024

Lab Report (3)

Helical Gear Cutting

No. Student Name Student I.D

1. Amal Mohamed Ali 1900261
2. Mohamed Nasr Mohamed Rfay 2100774
3. Mohamed Mosaad 1701288
4. Nour Mahmoud Mohamed AtTaher 1701592
5. Mustafa Rizq Abd-Elnazeer Ali 1900583
6. Taha Ayman Mohey Aldin Hassan 1900360

Remarks: Degree:

10
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.

Introduction:
Helical gears are essential components in various mechanical systems, renowned for their ability
to transmit power smoothly and efficiently. The process of manufacturing these gears demands
precision and expertise, particularly when employing milling machines. Helical gear cutting on
milling machines is a sophisticated method that combines the principles of rotary cutting with the
intricacies of helical gear geometry. This process involves the use of specialized tools and
techniques to carve out precise helical teeth on cylindrical workpieces, enabling the transmission
of rotational motion with reduced noise and smoother operation.

In this introduction, we'll delve into the fundamentals of helical gear cutting on milling
machines, exploring the key aspects of gear design, machining setup, tool selection, and the
sequential steps involved in the milling process. Understanding these principles is crucial for
engineers, machinists, and enthusiasts alike, as helical gears continue to play a pivotal role in
diverse industrial applications, from automotive transmissions to complex machinery in
manufacturing plants. Join us as we embark on a journey through the intricacies of helical gear
manufacturing, uncovering the art and science behind this essential mechanical process.

Fundamentals of Cutting Helical Gears on Milling Machines:

1. Gear Design and Calculations: The process of cutting helical gears begins with meticulous
design and calculations. Engineers must determine the gear specifications, including module,
pitch diameter, pressure angle, helix angle, and the number of teeth. These parameters influence
the gear's performance, strength, and meshing characteristics. Advanced software tools are often
employed to generate accurate gear profiles and calculate the necessary dimensions.

2. Machine Setup: Achieving precise helical gear cutting requires meticulous setup of the milling
machine. The workpiece must be securely mounted on the rotary table or indexing fixture,
ensuring proper alignment and stability. Additionally, the milling machine's axes must be
coordinated to accommodate the helix angle, allowing the cutter to follow the desired spiral path
during machining.

3. Tool Selection: Selecting the appropriate cutting tools is crucial for achieving accurate and
efficient gear cutting. Helical gear milling typically involves the use of special gear cutters with
angled teeth corresponding to the helix angle of the gear. These cutters may be single-tooth or
multi-tooth, depending on the application and the desired finish. Carbide or high-speed steel
(HSS) cutters are commonly used for their durability and precision.
4. Milling Process: The milling process for cutting helical gears involves a series of coordinated
movements to gradually shape the gear teeth. As the cutter rotates, it traverses along the
workpiece's axis while simultaneously moving radially to create the helical profile. This
synchronized motion ensures the accurate formation of each tooth, maintaining proper spacing
and alignment throughout the gear's circumference.

5. Feed and Speed Control: Controlling the feed rate and spindle speed is essential for achieving
optimal cutting performance and surface finish. The feed rate determines the rate of material
removal, while the spindle speed dictates the cutter's rotational speed. Adjustments may be made
based on the material being machined, cutter geometry, and desired cutting parameters to ensure
efficient chip removal and prevent tool wear.

6. Coolant and Lubrication: To mitigate heat generation and prolong tool life, coolant or
lubrication may be applied during the cutting process. Proper lubrication helps reduce friction
between the cutter and workpiece, preventing chip buildup and promoting smoother cutting
action. Coolant also aids in dissipating heat from the cutting zone, preventing thermal distortion
and maintaining dimensional accuracy.

Procedure of helical gear cutting:

1. Turn the given raw material 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.

The set up
Calculation
Given
Index plate

Side 1: 16, 17, 19, 21, 23, 29, 30, 31

Side 2: 33, 37, 39, 41, 43, 47, 49, 54

Gears

25, 30, 35, 40, 50, 55, 60, 70, 80, 90, 100

Lead Screw pitch = 4mm Z= 28 m= 1.75

Ψ= 14.5o β= 180

Solution
1) Blank Diameter= m(Z secβ+ 2) = 1.75(28 sec(18.7) +2) = 55.23 mm
𝒁 𝟐𝟖
2) ZV = = = 32.55 teeth
𝑪𝒐𝒔𝟑 𝜷 𝑪𝒐𝒔𝟑 (𝟏𝟖)
Cutter no 3 will be use
3) Depth of cut = 2.25 m = 2.25 x 1.75 = 3.9 mm
4) Indexing
𝟒𝟎 𝟑 𝟗
=𝟏 =𝟏
𝟐𝟖 𝟕 𝟐𝟏
The crank will be turn 1 complete Revolution
and 9 hole on circle 21 of the index plate
Figure 1 The index plates , the index crank
and the index arms
5) Gear ratio
Lead of the machine = 40 x 4 =160 mm
𝝅𝒙𝒁𝒙𝒎 𝝅 𝒙 𝟐𝟖 𝒙 𝟏.𝟕𝟓
Lead of gear = = = 498.2 ≅ 𝟒𝟖𝟎
𝑺𝒊𝒏 𝜷 𝑺𝒊𝒏 𝟏𝟖
𝝅 𝒙 𝟐𝟖 𝒙 𝟏.𝟕𝟓
Actual β = Sin-1 ( ) = 18.7o
𝟒𝟖𝟎
𝟏𝟖.𝟕−𝟏𝟖
Error = 𝒙 𝟏𝟎𝟎 = 3.9 % accepted
𝟏𝟖
𝟏𝟔𝟎 𝟏 𝟑𝟎
gear ratio = = =
𝟒𝟖𝟎 𝟑 𝟗𝟎

6) Milling calculations
 The total machining allowance At
At =2.25 M =2.25*1.75= 3.94 mm
 The roughing machining allowance Ar
Ar= At-Af=3.94- 0.44= 3.5 =mm
 Roughing
Ar = 3.5 mm
N= 130rpm
Ur = 12 mm/min
Dc= 100 mm
b= 40 mm
a (actual depth of cut) =3.5 mm
𝑏
Lr = ∆1 + 2√𝐷𝑐−𝑎2 + ∆2 +
𝑐𝑜𝑠𝛽
40
Lr = 2 + (2 ∗ √100 − (3.5)2 ) + 2 + = 64.96 mm
𝑐𝑜𝑠18.7
𝐴
i= 𝐼𝑛𝑡 ( ) = 1 pass
𝑎
L .i 64.96∗1
tm (roughing) = = = 5.41 min
u 12
 Finishing
Af = 0.75 mm
N= 210 rpm
Uf = 20 mm/min
Dc=100 mm
i = 1 pass
40
Lf = 2 + (2 ∗ √100 − (0.44)2 ) + 2 + 𝑐𝑜𝑠18.7 = 66.21 mm
L .i 66.21∗1
tm (finishing) = u
= 20
= 3.31 min
 7) Total M/c time
Estimated indexing time= 0.5 min/tooth
tm (total)=Z* (tm roughing+ tm finishing) + t indexing*(Z-1)
tm (total)= ( 28*( 3.31 + 5.41)) + (0.5*27)= 257.66 min

Operation sheet of the mandrel

Sheet No.: 1 No. of Sheets: 1
AIN SHAMS UNIVERSITY-FACULTY OF ENGINEERING DEPARTMENT OF DESIGN AND PRODUCTION ENGINEERING
Name of part : Mandrel

Code : 90318000
Process Description: Turning
M/C Tool: HSS RHT
No. of M/Cs per Operator:1
Type & Size of Input Material:
402*32 high carbon St
Total Basic Time: .62.3 (min.)
Time Allowance:

Standard Time per Piece:

Main M/Cg Dims. M/Cg Speeds & Feeds

Depth of Cut Setting Time Total Time
Allowance No. of Strokes
(mm) (min.) (min.)
(mm)
Basic M/cg
No. Operation Tool Type No. of Feed Rate
Time (min.)
Initial Final Feed Revs.
M/Cg Length Run in + Run Total Stroke Cutting Speed
Dimension Dimension (mm/rev.) (rev./min.) (mm/min.)
(mm) Out (mm) Length (mm) (m/min.)
(mm) (mm) (mm/stroke) (rev./stroke
)

1 Centering HSS RHT ___________________________________________________

2 Facing HSS RHT 402 400 16 4 20 1 1 1 0.05 28 300 15 1.3

3 longitudinal turning HSS RHT ∅32 ∅30 1 4 405 1 1 1 0.05 28 300 15 27

4 longitudinal turning HSS RHT ∅30 ∅22 100 2 102 4 1 4 0.05 18 200 10 10.2

5 longitudinal turning HSS RHT ∅22 ∅20 100 2 102 1 1 1 0.05 28 300 15 6.8

6 longitudinal turning HSS RHT ∅30 ∅22 100 2 102 4 1 4 0.05 18 200 10 10.2

7 longitudinal turning HSS RHT ∅22 ∅20 100 2 102 1 1 1 0.05 28 300 15 6.8
Operationsheets of the helical gear

Sheet No.: 1 No. of Sheets: 2

AIN SHAMS UNIVERSITY-FACULTY OF ENGINEERING DEPARTMENT OF DESIGN AND PRODUCTION ENGINEERING
Name of part : Helical Gear Blank

Code : 30.00

Process Description: Turning

M/C Tool: HSS RHT
No. of M/Cs per Operator:1

Type & Size of Input Material: S45C

Total Basic Time: 7.9 (min.)

Time Allowance: 56.00

Standard Time per Piece:

Main M/Cg Dims. M/Cg Speeds & Feeds

Depth of Cut Setting Time Total Time
Allowance No. of Strokes
(mm) (min.) (min.)
(mm)
Basic M/cg
No. Operation Tool Type No. of Feed Rate
Time (min.)
Initial Final Feed Revs.
M/Cg Length Run in + Run Total Stroke Cutting Speed
Dimension Dimension (mm/rev.) (rev./min.) (mm/min.)
(mm) Out (mm) Length (mm) (m/min.)
(mm) (mm) (mm/stroke) (rev./stroke
)

1 Centering HSS RHT __________________________

2 Facing HSS RHT 31 30 28 2 30 1 1 1 0.468 70.37 100 20 1.5

3 Longitudinal turning HSS RHT ∅56 ∅55.23 30 4 34 0.385 1 0.385 0.468 70.37 100 12 2.8

4 Drilling HSS Twist drill 0 ∅10 30 12 42 5 1 5 0.544 20 100 30 1.4

5 Boaring HSS Boaring ∅10 ∅30 30 13 43 10 1 10 0.544 20 100 20 2.2

Sheet No.: 2 No. of Sheets: 1

AIN SHAMS UNIVERSITY-FACULTY OF ENGINEERING DEPARTMENT OF DESIGN AND PRODUCTION ENGINEERING
Name of part : Helical Gear
Code : 84834021
Process Description: Milling
M/C Tool: RHT
No. of M/Cs per Operator:1
Type & Size of Input Material: S45C
Total Basic Time: 244.16 (min)
Time Allowance:

Standard Time per Piece: .

Main M/Cg Dims. M/Cg Speeds & Feeds

Depth of Cut Setting Time Total Time
Allowance No. of Strokes
(mm) (min.) (min.)
(mm)
No. Operation Tool Type No. of Feed Rate Basic M/cg
Time (min.)
Initial Final Feed Revs.
M/Cg Length Run in + Run Total Stroke Cutting Speed (rev./min.) (mm/min.)
Dimension Dimension (mm/rev.)
(mm) Out (mm) Length (mm) (m/min.) (rev./stroke
(mm) (mm) (mm/stroke)
)

1 Milling Roughing Gear cutter No.3 55.23 51.73 31.67 4 35.67 3.5 1 3.5 0.05 25 130 12 5.41

2 Milling finishing Gear cutter No.3 51.73 51.33 31.67 4 35.67 0.44 1 0.44 0.02 30 210 20 3.31

Repeat 28 times
Process Sheet of the Mandrel

Process Process Name Machine Basic Time

No. (min.)

1 Turning Center Lathe Machine 62.3

Process Sheet of the Helical gear

Process Process Name Machine Basic Time

No. (min.)

1 Turning Center Lathe Machine 7.9

2 Milling Horizontal Milling m/c 244.16