Sine Bars, Optical Comparators, and Fundamentals of Metal cutting & Machining Processes (Week 4)

Question 1

What is a Sine Plate or Bar?

Answer 1

A sine bar is used in conjunction with slip gauge blocks for precise angular measurement.

A sine bar is used either to measure an angle very accurately or face locate any work to a given angle.

This is an indirect method of angular measurement. They are frequently used for setting up angels from a horizontal plane.

Question 2

How do you calculate the height of the gauge blocks required to make an angle?

Answer 2

Calculate the sine of an angle, multiply by the length of the sine bar, and put the gauge block stack under the gauge block rod.

Question 3

What is 30° 20’ 15’’ in decimal?

Answer 3

30 + (20/60) + (15/3600) =
30.3375°

Question 4

What is 28° 52’ 37’’ in decimal?

Answer 4

28 + (52/60) + (37/3600) =
28.87694444…°

Question 5

What is 43° 34’ 32’’ in decimal?

Answer 5

43 + (34/60) + (32/3600) =
43.575555…°

Question 6

Using “Block Gauges” handout from Week 3 :

Calculate the gage blocks required for the following buildups: 7.8497 in.

Answer 6

0.1007, 0.149, 0.6, 3.0, 4.0

Question 7

Using “Block Gauges” handout from Week 3 :

What would the 10-inch gage block stack height be in inches for a ten-inch sine bar to attain an angle of 38 ͦ 37ʹ 36”?

Also Calculate the gauge blocks required for the buildup.

Answer 7

6.2424 in. →[0.1004, 0.142, 2.0, 4.0]

Question 8

When are Optical Comparators used?

Answer 8

Optical comparators are widely used for complex-shaped stampings, cams, gears, and threads, and compare to measured contour models.

In industries for measurements of machined parts such as gear parameters, thread parameters etc.

It’s also employed for inspecting and comparing very small and complex parts, which play a very significant role in the system’s structure.

Question 9

What are some of the important Applications of Optical Comparators?

Answer 9

Measurement of several linear and angular dimensions

All major dimensions of external screw threads, such as diameters, flank angle, lead, root and crest form, etc. can be inspected.

Question 10

Some benefits of using Optical Comparators :

1. Optical Comparator is _____________ measuring equipment where no physical contact with the object to be measured is required, eliminating the errors caused by __________ that result when physical pressure is applied to the object.
2. Optical comparators are _________ measuring systems that do not require regular check-ups to rule out wear and tear of the equipment.

Answer 10

1. Optical Comparator is [non-contact] measuring equipment where no physical contact with the object to be measured is required, eliminating the errors caused by [distortion] that result when physical pressure is applied to the object.
2. Optical comparators are [wear-free] measuring systems that do not require regular check-ups to rule out wear and tear of the equipment.

Question 11

What is Machining and the Material Removal Process?

Answer 11

Machining is a term used to describe a variety of material removal processes in which a cutting tool removes unwanted material from a workpiece to produce the desired shape/geometry.

The workpiece is typically cut from a larger piece of stock, which is available in a variety of standard shapes, such as flat sheets, solid bars, hollow tubes, and shaped beams.

Question 12

Machining – material removal by a ____________________________________, e.g., turning, milling, drilling. Machining can also be performed on an existing part, such as casting or forging.

Answer 12

Machining – material removal by a [sharp and harder (Harder than the workpiece) cutting tool], e.g., turning, milling, drilling. Machining can also be performed on an existing part, such as casting or forging.

Question 13

What are Abrasive processes?

Answer 13

material removal by hard, abrasive particles, e.g., grinding

Question 14

What are Nontraditional processes

Answer 14

various energy forms other than a sharp cutting tool to remove material.

Question 15

Mechanism of Metal Cutting

In metal cutting the metal is compressed and then plastically deformed as follows:

1. The tool ______________ the metal ahead of the tool when the workpiece moves on the face of the cutting tool
2. The compressed metal is then sheared whereby it slips. This process is known as ______________________.
3. As the cutting edge moves forward, the metal is strained at the cutting edge by what is known as the
   __________________________.
4. The concentration of stress at the cutting edge causes a
   _____________ (break by force from the workpiece)

Answer 15

Mechanism of Metal Cutting

In metal cutting the metal is compressed and then plastically deformed as follows:

1. The tool [compresses] the metal ahead of the tool when the workpiece moves on the face of the cutting tool
2. The compressed metal is then sheared whereby it slips. This process is known as [plastic deformation].
3. As the cutting edge moves forward, the metal is strained at the cutting edge by what is known as the
   [concentration of stress].
4. The concentration of stress at the cutting edge causes a
   [chip shear] (break by force from the workpiece)

Question 16

Define Plastic Deformation.

Answer 16

Plastic deformation is the deformation of the work material that occurs in the shear zone during cutting action.

Question 17

Define Plastic Flow.

Answer 17

Plastic flow is the flow of metal that occurs on the shear plane, which extends from the cutting-tool edge to the corner between the chip and the work surface.

Question 18

Define the Shear Zone.

Answer 18

The shear zone is the area where plastic deformation of the metal occurs. It is along a plane from the cutting edge of the tool to the original work surface.

Question 19

As far as metal cutting is concerned, What 3 surfaces define the geometry of the workpiece?

Answer 19

1. Work Surface to be removed (raw surface) geometry before cutting
2. Machined surface: surface produced by the metal cutting process (geometry after cutting)
3. Transient surface: surface formed on the workpiece and removed during the following cut

Question 20

Functions of Back Rake Angle?

Answer 20

• It helps to control the chip flow in a convenient direction.
• It reduces the cutting force required to shear the metal

Question 21

Functions of Side Rake angle?

Answer 21

• It performs similar functions as performed by the back-rake angle.
• The side rake angle along with the back-rake angle controls the chip flow direction.

Question 22

Functions of End Clearance (relief) Angle?

Answer 22

• It allows the tool to cut freely without rubbing against the work surface.
• Excessive relief angle reduces the strength of the tool.

Question 23

Functions of Side Clearance (relief) Angle?

Answer 23

• It avoids the rubbing of the flank against the workpiece
• It maintains that no part of the tool besides the actual cutting edge can touch the work.

Question 24

Functions of End Cutting Edge Angle?

Answer 24

• It avoids rubbing between the edge of the tool and the workspace.
• It influences the direction of chip flow.

Question 25

Functions of Nose Radius?

Answer 25

• A sharp point at the end of the tool is undesirable because it is highly stressed, short-lived, and leaves grooves in the path of the cut.
• If the nose radius is too large chatter will occur.