##### Document Text Contents

Page 121

114 Chapter 3

II

I.

A

.9

2. Rp is the maximum profile height from the mean line within the

sampling length. Rpm is the mean value of Rp’s determined over

five sampling lengths.

3. PC (peak count) is the number of peak/valley pairs per inch projecting

through a band of width b centered about the mean line.

optical flats. Light waves of any kind are of invariable length and are the stan-

dards for ultimate measures of distance. Basically, all interferometers divide a

light beam and send it along two or more paths. Then the beams are recombined

and always show interference in some proportion to the differences between

the lengths of the paths. One of the simplest illustrations of the phenomenon is the

optical flat and a monochromatic light source of known wavelength.

The optical flat is a plane lens, usually a clear fused quartz disk, from about

51–254 mm (2–10 in) in diameter and 13–25 mm (.5–1 in) thick. The faces of a flat

are accurately polished to nearly true planes; some have surfaces within 25 nm

(.000001 in) of true flatness.

Helium is commonly used in industry as a source of monochromatic or single-

wavelength light because of its convenience. Although helium radiates a number

of wavelengths of light, that portion that is emitted with a wavelength of 587 nm

(.00002313 in) is so much stronger than the rest that the other wavelengths are

practically unnoticeable.

The principle of light-wave interference and the operation of the optical flat

are illustrated in Figure 3.28a wherein an optical flat is shown resting at a slight

angle on a workpiece surface. Energy in the form of light waves is transmitted

from a monochromatic light source to the optical flat. When a ray of light reaches

the bottom surface of the flat, it is divided into two rays. One ray is reflected

from the bottom of the flat toward the eye of the observer, while the other contin-

ues on downward and is reflected and loses one-half wavelength on striking the

top of the workpiece. If the rays are in phase when they re-form, their energies

reinforce each other, and they appear bright. If they are out of phase, their energies

cancel and they are dark. This phenomenon produces a series of light and dark

fringes or bands along the workpiece surface and the bottom of the flat, as illus-

trated in Figure 3.28b. The distance between the workpiece and the bottom surface

of the optical flat at any point determines which effect takes place. If the distance

is equivalent to some whole number of half wavelengths of the same monochro-

matic light, the reflected rays will be out of phase, thus producing dark bands.

This condition exists at positions X and Z of Figure 3.28a. If the distance is equiv-

alent to some odd number of quarter wavelengths of the light, the reflected rays

will be in phase with each other and produce light bands. The light bands would

be centered between the dark bands. Thus a light band would appear at position

Y in Figure 3.28a.

Since each dark band indicates a change of one-half wavelength in distance

separating the work surface and flat, measurements are made very simply by

counting the number of these bands and multiplying that number by one-half

the wavelength of the light source. This procedure is illustrated in Figure 3.28b.

There, the diameter of a steel ball is compared with a gage block of known height.

Page 240

Index Terms Links

This page has been reformatted by Knovel to provide easier navigation.

total quality cost 7

traceability

equipment 121

product 147

transfer standard 129

transfer type instruments 138

type I error 129

type II error 129

U

u-chart 64

ultrasonic testing 149

unilateral tolerance 132

universe, definition 35

V

value stream map 14

variable 135

variable inductance transducer 104

variable transformer 105

variables, acceptance sampling by 157

variables charts 57 59

variables sampling plans 161

variance 46

variation 44

common cause 68

in processes 3 4

special cause 68

venturi gage 105

verification inspection 144

vernier caliper 77

vernier height gage 79

Page 241

Index Terms Links

This page has been reformatted by Knovel to provide easier navigation.

vernier micrometer caliper 81

Vickers hardness test 151

virtual teams 33

W

wear allowance, for gages 90

weight 107

working gage 84

working papers, audit 171 175

working standard 128

X

and R chart 57

X-ray testing 149

Z

Z, standard normal distribution

for select values of (Appendix F) 207

X –

114 Chapter 3

II

I.

A

.9

2. Rp is the maximum profile height from the mean line within the

sampling length. Rpm is the mean value of Rp’s determined over

five sampling lengths.

3. PC (peak count) is the number of peak/valley pairs per inch projecting

through a band of width b centered about the mean line.

optical flats. Light waves of any kind are of invariable length and are the stan-

dards for ultimate measures of distance. Basically, all interferometers divide a

light beam and send it along two or more paths. Then the beams are recombined

and always show interference in some proportion to the differences between

the lengths of the paths. One of the simplest illustrations of the phenomenon is the

optical flat and a monochromatic light source of known wavelength.

The optical flat is a plane lens, usually a clear fused quartz disk, from about

51–254 mm (2–10 in) in diameter and 13–25 mm (.5–1 in) thick. The faces of a flat

are accurately polished to nearly true planes; some have surfaces within 25 nm

(.000001 in) of true flatness.

Helium is commonly used in industry as a source of monochromatic or single-

wavelength light because of its convenience. Although helium radiates a number

of wavelengths of light, that portion that is emitted with a wavelength of 587 nm

(.00002313 in) is so much stronger than the rest that the other wavelengths are

practically unnoticeable.

The principle of light-wave interference and the operation of the optical flat

are illustrated in Figure 3.28a wherein an optical flat is shown resting at a slight

angle on a workpiece surface. Energy in the form of light waves is transmitted

from a monochromatic light source to the optical flat. When a ray of light reaches

the bottom surface of the flat, it is divided into two rays. One ray is reflected

from the bottom of the flat toward the eye of the observer, while the other contin-

ues on downward and is reflected and loses one-half wavelength on striking the

top of the workpiece. If the rays are in phase when they re-form, their energies

reinforce each other, and they appear bright. If they are out of phase, their energies

cancel and they are dark. This phenomenon produces a series of light and dark

fringes or bands along the workpiece surface and the bottom of the flat, as illus-

trated in Figure 3.28b. The distance between the workpiece and the bottom surface

of the optical flat at any point determines which effect takes place. If the distance

is equivalent to some whole number of half wavelengths of the same monochro-

matic light, the reflected rays will be out of phase, thus producing dark bands.

This condition exists at positions X and Z of Figure 3.28a. If the distance is equiv-

alent to some odd number of quarter wavelengths of the light, the reflected rays

will be in phase with each other and produce light bands. The light bands would

be centered between the dark bands. Thus a light band would appear at position

Y in Figure 3.28a.

Since each dark band indicates a change of one-half wavelength in distance

separating the work surface and flat, measurements are made very simply by

counting the number of these bands and multiplying that number by one-half

the wavelength of the light source. This procedure is illustrated in Figure 3.28b.

There, the diameter of a steel ball is compared with a gage block of known height.

Page 240

Index Terms Links

This page has been reformatted by Knovel to provide easier navigation.

total quality cost 7

traceability

equipment 121

product 147

transfer standard 129

transfer type instruments 138

type I error 129

type II error 129

U

u-chart 64

ultrasonic testing 149

unilateral tolerance 132

universe, definition 35

V

value stream map 14

variable 135

variable inductance transducer 104

variable transformer 105

variables, acceptance sampling by 157

variables charts 57 59

variables sampling plans 161

variance 46

variation 44

common cause 68

in processes 3 4

special cause 68

venturi gage 105

verification inspection 144

vernier caliper 77

vernier height gage 79

Page 241

Index Terms Links

This page has been reformatted by Knovel to provide easier navigation.

vernier micrometer caliper 81

Vickers hardness test 151

virtual teams 33

W

wear allowance, for gages 90

weight 107

working gage 84

working papers, audit 171 175

working standard 128

X

and R chart 57

X-ray testing 149

Z

Z, standard normal distribution

for select values of (Appendix F) 207

X –