Shop Computation

8/10/2019 Shop Computation

http://slidepdf.com/reader/full/shop-computation 1/34



MIRDC-ITS Slide 2

OBJECTIVE

At the end of the course, the participants

shall be able to perform basic computation

in machining.



MIRDC-ITS Slide 3

COURSE OUTLINE

Introduction to Measurement

Shop Calculations

- Cutting Speed

- Feed

Machine Shop Application



MIRDC-ITS Slide 4

Measurement

• defined as the estimation of some

attribute of an object, such as its length

or weight, relative to a unit ofmeasurement.

• it is expressed in terms of length,

volume, area, temperature, among

others.



MIRDC-ITS Slide 5

Systems of Measurement

• English System

• System Internationale (SI) or Metric System



MIRDC-ITS Slide 6


• English System

grew out of the creative way that people

measured for themselves. Familiar

objects and parts of the body were used

as measuring devices.



MIRDC-ITS Slide 7


• English System

Length:

12 inches (in) = 1 foot (ft)3 feet = 1 yard (yd)

5280 feet = 1 mile (mi)

Capacity:

3 teaspoons (tsp) = 1 tablespoon (tbsp)

16 tbsp = 1 cup (c)

8 ounces (oz) = 1 c

2 c = 1 pint (pt)

2 pt = 1 quart (qt)4 qt = 1 gallon (gal)

Weight: 16 ounces (oz) = 1 pound (lb)

2000 lb = 1 ton



MIRDC-ITS Slide 8


• Metric System

developed at the time of the French

Revolution, with standards set for the

meter and kilogram on June 22, 1799.

it was an elegant decimalsystem, where units of like type

were defined by power of ten.



MIRDC-ITS Slide 9


• SI (Metric System)

Meter (m); Kilogram (kg); Second

(s); Ampere (amp); Kelvin (°K); Mole

(mol); Candela (cd).

From these base units, manyother units are derived.

Ex: Velocity – meter per second



MIRDC-ITS Slide 10

Conversion of Measurement



MIRDC-ITS Slide 11




MIRDC-ITS Slide 12




MIRDC-ITS Slide 13

REVIEW AND EXERCISES



MIRDC-ITS Slide 14

Convert the following:

Given:

1 cm = 10 mm 1 ft = 12 in

1 m = 100 cm 1 mi = 5280 ft

1 km = 1000 m 1 in = 2.54 cm

1.) 10 ft = ______ m 4.) 27 in = ____ mm

2.) 18 mi = ______ km 5.) 1.5 mi = ____ m

3.) 8 m = _______ ft 6.) 37 km = _____ mi



MIRDC-ITS Slide 15

MACHINE SHOP COMPUTATION



MIRDC-ITS Slide 16

Cutting Speed (CS)

• defined as the length or distance which

the tool point of a machine cuts in one

minute.• it is expressed in units of distance

along the work-piece surface per unit of

time (surface feet per minute or meters

per minute).

CS = D N



MIRDC-ITS Slide 17

Cutting Speed (CS)

where:pi = 3.1416

D = diameter

N = rpm (revolution per minute)

CS = D N



MIRDC-ITS Slide 18

High-Speed Steel Cutter Carbide Cutter Material ft/min m/min ft/min m/min

Alloy steel 40 –70 12 –20 150 –250 45 –75

Aluminum 500 –1000 150 –300 1000 –2000 300 –600

Bronze 65 –120 20 –35 200 –400 60 –120

Cast iron 50 –80 15 –25 125 –200 40 –60

Mach steel 70 –100 21 –30 150 –250 45 –75

Stnless steel 30 –80 10 –25 100 –300 30 –90

Tool steel 60 –70 18 –20 125 –200 40 –60

Milling Machine Cutting Speeds



MIRDC-ITS Slide 19

Cutting Speed (CS)

Calculate the cutting speed in ft/min of acutting tool in a lathe that cuts a 5 ½ inch

steel that is revolving at a rate of 150 rpm.

Example No. 1:

Answer: 215.99 ft/min



MIRDC-ITS Slide 20

Cutting Speed (CS)

What is the cutting speed in m/min of a toolthat cuts a 105 mm stock if the lathe makes

190 rpm?

Example No. 2:

Answer: 62.67 m/min



MIRDC-ITS Slide 21

RPM Calculation (English)

For optimum use of cutter, proper speed(rpm) must be determined

Diameter of cutter affects the speed

D

xCS

x

xCS

xinncecircumfere

ftCSr 4141633

1214163390

...)()(min/

Calculate speed required to revolve a 3-in. diameterhigh-speed steel milling cutter for cutting machine

steel (CS=90 sf/min).simplified formula

1203

360

3

904

xr min/



MIRDC-ITS Slide 22

RPM Calculation (Metric)

Formula for r/min of the milling machine using

metric measurement

)()(

x.D(mm)x)(min/

mmDxmCS

DCSxxmCSr 32014163

10001000

simplified formula

Calculate the r/min required for a 75 mm diameter

high-speed steel milling cutter when cutting

Machine steel (CS 30 m/min)

12875

9600

75

32030min/

x

r



MIRDC-ITS Slide 23

Cutting Speed Rules for Best Results

1. For longer cutter life, use lower CS in

recommended range

2. Know the hardness of the material to be machined3. When starting, use lower range of CS and

gradually increase to higher range

4. Reduce feed instead of increasing the cutter speedfor fine finish

5. Using coolant will generally produce better finish

and lengthen cutter life



MIRDC-ITS Slide 24

Feed

• defined as the distance the cutting tool

advances along the length of the work

for every revolution.• the feed of an engine lathe is

dependent on the speed of the lead

screw or feed rod.

• expressed in inches per minute /

meters per minute



MIRDC-ITS Slide 25

Feed

Feed Rate = RPM x Chip Load x No. of Teeth

where:RPM = spindle speed

Chip Load = thickness of material removed

by each cutting edge

No. of Teeth = number of cutting edges/inserts



MIRDC-ITS Slide 26



MIRDC-ITS Slide 27

Example No. 1:

Feed

Find the feed in inches per minute using a

3.5 in. diameter, 12 tooth helical cutter to

cut machine steel (CS80)First, calculate proper r/min for cutter:

9153

8044

.

min/

x

D

CSxr

Feed(in/min) = N x CPT x r/min

=12 x .010 x 91

= 10.9 or 11 in/min



MIRDC-ITS Slide 28

Example No. 2:

Feed

Calculate the feed in millimeters per minute

for a 75-mm diameter, six-tooth helical carbide

milling cutter when machining cast-iron (CS 60)First, calculate proper r/min for cutter:

25675

20019

755

32060320

,min/

x

D

xCSr

Feed(in/min) = N x CPT x r/min

= 6 x .025 x 256

= 38.4 mm/min



MIRDC-ITS Slide 29

MACHINE SHOP APPLICATIONS



MIRDC-ITS Slide 30

Taper

A work is said to be tapered when the

dimensions of the cross section of a

piece of work, or a part of a work, isgradually and uniformly increasing or

decreasing from both ends.



MIRDC-ITS Slide 31

Taper

The taper on a piece of work is formed by

subtracting the diameter of the small

end from the diameter of the large end.

d D

Taper = D - d



MIRDC-ITS Slide 32

Taper

The taper per inch of a piece of work is

the taper divided by the length in

inches.

d D

L

Taper per inch = D – d

L



MIRDC-ITS Slide 33

Taper

The taper per foot of a piece of work is the

taper divided by the length in feet.

d D

L

Taper per foot = taper per inch x 12



THANK YOU.

MIRDC-ITS Slide 34

Shop Computation

Documents

Transcript of Shop Computation