Shop Exercise 8 Indab

Mapúa Institute of Technology
Muralla St., Intramuros, Manila

Department of Mechanical and Manufacturing Engineering
SHOP PRACTICE NO. 08

MILLING PRACTICE (SPUR GEAR)
YATAL, Kristine G.
MFGE-2
ME137L/A2
2015100716
GRADE
Group# 3
Engr. Jose V. Hernandez

Instructor
Shop Practice No. 8
SPUR GEAR AND BEVEL GEAR
OBJECTIVE:
1. To familiarize the students with the milling machine and its parts.
2. To familiarize the students with the basic operation of the milling machine.
3. To familiarize the students with the gearing operation of the milling machine.
4. To be able to manufacture a spur gear.
METHODS AND ANALYSIS:

The advent transformation of the wheel by adding teeth on its circumferential surface has
made possible the transfer of motion to another gear or rack. It is through the understanding of the
basic design computation and actual fabrication of gears that one can fully appreciate the use of
this basic spare part and the machine that produces it.
MATERIALS:
50mm diameter x 30mm Wooden Block
50mm diameter x 80mm Wooden Block
TOOLS AND MECHINES TO BE USED:

o Milling Machine
o Bolt and Nut
o Sandpaper
o Universal Chuck
o Wrench Driver
PROCEDURE:
1. Prepare the materials and equipment needed.

2. Compute for the simple indexing needed for the 13-teeth spur gear and zero bevel gear
which is 3 revolutions and 3 holes in a 39-set holes index plate.
3. Clamp the formed wooden material, for the zero-bevel gear, to the chuck of the index
head with the index pin at the top most hole of the 39-set holes and set the sector arm in
place.
4. Turn on the milling machine, then adjust the height of the saddle/table and the depth of
cut for the first gear.
5. Let the chuck travels horizontally with the table to complete each cut.
6. Rotate the index crank 3 times and pass 3 holes from the previous hole.
7. repeat step number five and six until the wooded gear is already finish.
8. Turn off rotating milling cutter and remove the newly cutter gear.
9. Clean it with a sand paper.
10. Insert the second wooden pattern to the correct sized bolt-rod and lock it with a
corresponding nut.
11. Adjust the inclination of the index head’s chuck until it faces horizontally.
12. Clamp the bolt-rod with the wood pattern on it to the chuck and secure it with the tail
stock center.
13. Set the index pin again on the top most hole of the 39-set holes of the faceplate and
adjust the sector arm in place.
14. Turn on the milling cutter and adjust again the height of the saddle/table and the depth
of cut.
15. Let the chuck travels horizontally with the table to complete each cut.
16. Repeat stem number five and six until the gear is finished.
17. Turn off the milling machine and unclamp the bolt-rod with the wooden gear.
18. Remove the gear from the bolt-rod and clean it with a sand paper.
19. Write the section of the class of the gears and submit them.
QUESTIONS:
1. What is a milling machine?
- Milling machines are tools designed to machine metal, wood, and other solid materials.
Often automated, milling machines can be positioned in either vertical or horizontal
orientation to carve out materials based on a pre-existing design.
2. What are the two main kinds of milling machines and what are their differences?
- The main kinds of milling machines are the horizontal milling machine and the vertical
milling machine.
- In the vertical milling machine, the spindle axis is vertically oriented. Milling cutters are
held in the spindle and rotate on its axis. The spindle can generally be extended (or the
table can be raised/lowered, giving the same effect), allowing plunge cuts and drilling.
There are two subcategories of vertical mills: the bed mill and the turret mill.
- On the other hand, a horizontal milling machine has the same sort but the cutters are
mounted on a horizontal arbor across the table. Many horizontal mills also feature a built-
in rotary table that allows milling at various angles; this feature is called a universal table.
While endmills and the other types of tools available to a vertical mill may be used in a
horizontal mill, their real advantage lies in arbor-mounted cutters, called side and face
mills, which have a cross section rather like a circular saw, but are generally wider and
smaller in diameter.
3. What are the main parts of a milling machine?

•Base
•Column
•Saddle
•Knee
•Table
•Front brace
•Overhanging arm
•Arbor
•Spindle
4. What is indexing?
- Indexing in reference to motion, is moving into a new position or location quickly and
easily but also precisely. After a machine part has been indexed, its location is known to
within a few hundredths of a millimeter (thousandths of an inch), or often even to within a
few thousandths of a millimeter (ten-thousandths of an inch), despite the fact that no
elaborate measuring or layout was needed to establish that location. Indexing is a necessary
kind of motion in many areas of mechanical engineering and machining. A part that
indexes, or can be indexed, is said to be indexable.
5. What is a gear?
- A gear is a toothed wheel that work together to alter the relation between the speed of a
driving mechanism (such as the engine of a vehicle or the crank of a bicycle) and the
speed of the driven parts (the wheels).
6. What does the circular pitch of a spur gear mean?

Circular pitch is the distance between corresponding points of consecutive gear teeth
measured along the pitch circle.
7. What does the diametral pitch of a spur gear mean?

- It is the number of teeth of a gear per inch of its pitch diameter. A toothed gear must have
an integral number of teeth. The circular pitch, therefore, equals the pitch circumference
divided by the number of teeth.
8. On gears that has the same diametral pitch, will they have the same size and
thickness of teeth on the pitch circle even if they have different outside diameters?
Why?
- Yes, because they will have the same size and thickness on the pitch circle even if they
have different outside diameters.
9. What is the addendum of a gear?

- The addendum is the height by which a tooth of a gear projects beyond
(outside for external, or inside for internal) the standard pitch circle or pitch line; also, the
radial distance between the pitch diameter and the outside diameter.
10. What is the rule for changing diametral pitch to circular pitch?
- To change diametral pitch to circular pitch, the formula is pi times the inverse of diametral
𝜋𝐷
pitch. 𝑝 = 𝑁 , where p is the circular pitch, D is the pitch diameter and N is the number of
teeth
Front View
Scale 1:1
Unit: mm
Side View / Top View

Scale 1:1
Unit: mm
Isometric View
Scale 1:1
Unit: mm
DISCUSSION:
A gear or cogwheel is a rotating machine part having cut teeth, or cogs, which mesh with
another toothed part to transmit torque. Geared devices can change the speed, torque, and
direction of a power source. Gears almost always produce a change in torque, creating a
mechanical advantage, through their gear ratio, and thus may be considered a simple machine.
The teeth on the two meshing gears all have the same shape. Two or more meshing gears,
working in a sequence, are called a gear train or a transmission. A gear can mesh with a linear
toothed part, called a rack, thereby producing translation instead of rotation.
The gears in a transmission are analogous to the wheels in a crossed, belt pulley system.
An advantage of gears is that the teeth of a gear prevent slippage.
When two gears mesh, if one gear is bigger than the other, a mechanical advantage is
produced, with the rotational speeds, and the torques, of the two gears differing in proportion to
their diameters.
In transmissions with multiple gear ratios—such as bicycles, motorcycles, and cars—the
term "gear" as in "first gear" refers to a gear ratio rather than an actual physical gear. The term
describes similar devices, even when the gear ratio is continuous rather than discrete, or when
the device does not actually contain gears, as in a continuously variable transmission.
Early examples of gears date from the 4th century BCE in China (Zhan Guo times – Late
East Zhou dynasty), which have been preserved at the Luoyang Museum of Henan Province,
China. The earliest gears in Europe were circa CE 50 by Hero of Alexandria, but they can be
traced back to the Greek mechanics of the Alexandrian school in the 3rd century BCE and were
greatly developed by the Greek polymath Archimedes (287–212 BCE)
The definite velocity ratio that teeth give gears provides an advantage over other drives
(such as traction drives and V-belts) in precision machines such as watches that depend upon an
exact velocity ratio. In cases where driver and follower are proximal, gears also have an
advantage over other drives in the reduced number of parts required; the downside is that gears
are more expensive to manufacture and their lubrication requirements may impose a higher
operating cost per hour.
Numerous nonferrous alloys, cast irons, powder-metallurgy and plastics are used in the
manufacture of gears. However, steels are most commonly used because of their high strength-
to-weight ratio and low cost. Plastic is commonly used where cost or weight is a concern. A
properly designed plastic gear can replace steel in many cases because it has many desirable
properties, including dirt tolerance and low speed .
CONCLUSION:
The students were able to manufacture a spur and bevel gear. It is due to the
familiarization and knowledge of the students about the milling machine and its parts also the
basic and gearing operation of the milling machine.
RECOMMENDATION:
I recommend that the students should learn more about the computation in changing the
diametric and circular pitch so that there will be no problems in creating a gear. Also in doing the
computation, the students must be careful because the computation is an important factor in
producing a gear. Ensure as well that the vertical-horizontal milling machine is working
correctly, as well as the other tools involved, in order to lessen the risk of having accidents in this
shop practice.
REFERENCE:
 https://en.wikipedia.org/wiki/Milling_(machining)
 http://www.sabah.edu.my/cwm019/Index_files/page0039.htm
 https://en.wikipedia.org/wiki/Indexing_(motion)
 https://en.wikipedia.org/wiki/Gear
 https://www.merriam-webster.com/dictionary/circular%20pitch
 https://www.cs.cmu.edu/~rapidproto/mechanisms/chpt7.html
 http://machinedesign.com/technologies/gear-quality-what-its-all-about

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Mapúa Institute of Technology

Muralla St., Intramuros, Manila

SHOP PRACTICE NO. 08

Engr. Jose V. Hernandez

METHODS AND ANALYSIS:

TOOLS AND MECHINES TO BE USED:

1. Prepare the materials and equipment needed.

3. What are the main parts of a milling machine?

6. What does the circular pitch of a spur gear mean?

7. What does the diametral pitch of a spur gear mean?

9. What is the addendum of a gear?

Side View / Top View

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