FIGURE 22.6 ■ Pipe thread designation.

Dimensioning data for American Standard Pipe Threads is applied in the same form to both metric and nonmetric drawings. There are two types of designations for this thread: National Pipe Taper (NPT) and National Pipe Straight (NPS). The NPT thread is a tapered thread with a taper of 0.75" per foot. The NPS thread is a straight thread. Each type has application for particular types of joint requirements. The included angle of a pipe thread form is 60°.

Nominal Size	Pitch	C T	oarse Fine hread Thread
4	0.7		M4		M4 x 0.5
5	0.8		M5		M5 x 0.5
6	1		M6		M6 x 0.75
7	1		M7		M7 x 0.75
8	1.25		M8 ........		M8x 1
9	1.25		M9		M9x 1
10	1.5		M10		M10x 1.25
12	1.75		M12		M12 x 1.25
16	2		M16		M16 x 1.5
20	2.5		M20		M20x1.5
24	3		M24		M24x2

TABLE 22.5 ■ Listing of coarse and fine metric thread sizes.

The manner in which National Pipe Threads are designated is illustrated in Figure 22.6. It should be noted that National Pipe Threads derive their sizes from the nominal sizes of the pipe to which the threads are applied.

A list of coarse and fine metric thread sizes is shown in Table 22.5. Note that for coarse threads (also sometimes identified as standard metric threads), prefix M and the diameter (in millimeters) is used for specifying the thread.

For fine threads, the prefix M, diameter (in millimeters), and the pitch (in millimeters) must be used. The pitch represents the distance from the crest of one thread to the crest of the next thread.

MATERIALS IN METRIC SIZES

Many components shown on metric prints can be fabricated from materials that are available in standard metric sizes. However, when mate­rials in metric sizes are not available, materials in inch sizes that most closely match the metric sizes are used. In certain cases, it may be neces­sary to machine the material to the metric size required. This is true particularly when there is a significant difference between the inch size material that is available and the metric sizes that are specified for a fabrication.

As more materials become available in standard metric sizes, the problem of conversion will be reduced. In the meantime, the welder should be able to convert metric to inch and inch to metric dimensions to select material sizes that will be most economical in the fabrication of a weldment.

The most common metric value found on a print is the millimeter. Tables of inch-millimeter conversions are contained in Appendix 1. Mathematical constants that may be used for making conversions, in the event conversion tables are not available, are shown in Table 22.6

Note that when converting an inch value to a millimeter value a multiplication process is used. The same constants may be used to convert a metric value to an inch value. In this case, the inch value is divided by the appropriate constant. Examples of these processes follow (the underlined figures are the constants):

Inch(es) to millimeter(s)

Linear Conversion
From	To		Multiply by
inches	millimeters		25.4
feet .	meters		0.305
yards	meters		0.914
Area Conversion
square inches	square millimeters		645.2
square feet	square meters		0.093
square yards	square meters		0.836
Volume Conversion
cubic inches	cubic millimeters		1.639
cubic feet	cubic meters		0.028

TABLE 22.6 ■ Constants for metric conversions.

Square feet to square meter(s)

20 square feet X 0.093 = 1.86 m2 (square meters)

Cubic inch(es) to cubic millimeter(s)

20 cubic inches X 1.639 = 19.668 mm3 (cubic meters)

Millimeter(s) to inch(es)

173 mm 25.4 = 6.811 inches

Square meter(s) to square feet 14 m2 0.093 = 150.537 square feet

Cubic meter(s) to cubic feet

20 m3 0.028 = 714.285 cubic feet

STANDARD PRACTICES FOR PRESENTING METRIC EXPRESSIONS AND DIMENSIONS ON METRIC DRAWINGS FOR WELDMENTS

■ When a millimeter dimension is less than 1, a “0” is shown preceding the decimal point. Note that the abbreviation “mm” is not used when applying a metric dimension to a welding symbol; rather it is so in­dicated by a general note on the print.

Example:

Correct Incorrect

0. 08 mm.08 mm

■ A decimal point and a zero are not shown when the millimeter dimension is a whole number.

Example:

Correct Incorrect

8 mm 8.0 mm

■ A millimeter dimension with a whole number and a decimal fraction is not shown with a 0 following the decimal fraction. However, this practice does not apply to tolerance dimensioning.

Example:

Correct 2.2 mm

Incorrect 2.20 mm

■ A metric dimension is given as a decimal fraction rather than a common fraction. Example:

Preferred 0.625 mm

Obsolete 5 — mm 8

■ An “s” is not added to a symbol to make it plural. The symbol without an “s” represents both singular and plural units.

Example:

Correct 16 mm

Incorrect 16 mms

■ Symbols for metric units are shown in lowercase letters, except for units derived from the names of people. Example:

Correct 6 mm

Incorrect 6 Mm

■ Metric tolerances are shown on a drawing with the positive tolerance placed above the minus tolerance. A zero tolerance is indicated by a 0, whether it be plus or minus.

Examples:

Correct

Incorrect

■ Drawings dimensioned in millimeters will not show the digits separated into groups by commas or spaces. Examples:

Correct 1650 12570

Incorrect 1,650 12 570

■ When all dimensions on a drawing are shown in millimeters, an identification of each dimension by the abbreviation “mm” is not required. The same applies when all dimensions are in inches. That is, the “IN” abbreviation is not used following each dimension. However, when some inch dimensions are included on a millimeter-dimensioned drawing, the abbreviation “IN” is used after each inch value. Also, when some millimeter dimensions are applied to an inch-dimensioned drawing, the abbreviation “mm” is applied following each millimeter value. Notes, as shown below, are applied to the drawing to clarify the application of millimeter and inch values. Note: Unless otherwise specified, all dimensions are in millimeters. Note: Unless otherwise specified, all dimensions are in inches. ■ A semicolon is used rather than a comma to separate metric dimensions that are shown in sequence.

Example:

Correct Incorrect

28 mm; 16 mm; 5 mm 28 m, 16 mm, 5 mm

■ When a note or specification indicates that SI units are to be multiplied, a raised dot (•) is included be­tween symbols in place of a times (X) sign. However, a raised dot is not used between numbers because it may be misinterpreted as a decimal point. A times sign (X) is used to indicate multiplication of numbers.

Example:

Correct Incorrect

C = A-S C = A X S

17 X 25 17-25

■ Metric prefixes shown on a drawing or in specifications will generally remain the same throughout. They are not mixed in one expression. In most cases the prefix “milli” is used. Variations in its value are ac­complished by changing the location of the decimal point in the numbers being expressed.

Examples:

Correct Incorrect

6 mm long 6 mm long

X 20 mm high X 0.02 m high

■ When converting an inch dimension not having a tolerance to a millimeter equivalent, the conversion is made to the same preciseness or better. For more examples, see Table 22.7.

Example:

Correct 16.50” = 419.10 mm

Incorrect 16.50” = 419 mm

Electrode Sizes	Fillet Sizes
in.	mm	in.	mm
0.030	0.76	1/8	3
0.035	0.89	5/32	4
0.040	1.02	3/16	5
0.045	1.14	1/4	6
1/i6	1.59	5/l6	8
5/64	1.98	3/8	10
3/32	2.38	7 he	11
V 8	3.18	1/2	13
5/32	3.97	5/8	16
3/16	4.76	3/4	19
>	6.35 ^	7/8	22
/	— —....	1	25
/ U. S. Customary (inch)	N Metric (millimeters)
TABLE 22.7 ■ Conversion tables.

■ Dual dimensioning including U. S. Customary units (common and/or decimal fractions) and millimeter units may also be found on prints; however, it is not standard practice.

Example:

)

UNIT 22: REVIEW A

1. For the following items, select those metric expressions that are presented incorrectly and revise them so they are correct.

a. 43/4 mm

b. .10 mm

c. 18.67 mm

Name	Quantity Represented	Symbol
ampere	length	m
	kg K
Celsius
	mm2
volt
	rad

d. 16 ± .05 mm

e. 16% mms. ,

4. a. What is the included angle of a radian?

f. All tolerances, unless otherwise specified, are + }0mm

b. Does it apply to the measurement of plane angles or solid angles?

j. 100 mm X 10 m X 25 mm

h. 30 mm dia. X 20 mm

5. What is the preferred method for showing the following dimensions on a metric drawing?

a. 26° 35' 22"

b. .758"

c. 0.08736 mm

d. 68[5]/2 square inches______________________

6. What is the included angle of a metric screw thread form?

<

<s

7. Interpret the significance of each element of the following screw thread designations.

a.

SPEC "A” - ALL FILLET WELDS TO BE 13 mm

*

3. Fill in the missing elements in the following table.

8. Make the following conversions.

a. 2.500" =______________________________ mm

b. 6 square inches c. 2.2 radians =_____________ d. 0.8 radian =

square millimeters

degrees

degrees

9. What is the area in square millimeters for the following shapes? Round answers to one decimal place.

10. How many millimeters of weld are required in each of the following sketches? Round answers to nearest millimeter.

13. What is the spacing of each of the following welds in millimeters? Round answers to the nearest millimeter.

гЄтг-

a.

/

200 з" (8)

	I I 35 mm * 1
	l Г
	L-12 mm L
	Г

/

0.25" Q 2" (4)

11. How many square millimeters of surface weld are required? Do not include the area of the hole. Round answer to nearest millimeter.

c —7~{и±Гё"

12. What is the size of each of the following welds in millimeters? Round answers to the nearest millimeter.

14. What is the pitch and length of the following welds in millimeters? Round answers to the nearest millimeter.

Pitch ___________________________________________________________

Length _________________________________________________________

15. How many degrees are indicated for each of the following angular dimensions? Round answers to the nearest degree.

16. a. What is the volume in cubic millimeters of the cylinder illustrated? Round answer to the nearest cubic millimeter.

b. How many millimeters of weld are required to fabricate the cylinder? Round answer to nearest millimeter.

1 7. a. What is the area in square millimeters

circumscribed by the broken lines in the following sketch at the top of next column? Round answer to the nearest square millimeter.

b. What is the perimeter of the area

circumscribed by broken lines? Round answer to nearest millimeter.

c. What kind of weld is required?

Note: All linear and welding symbol dimensions are in millimeters.

18. a. What is the volume in cubic millimeters of the tank illustrated below? Round answer to the nearest cubic millimeter.

b. How many millimeters of weld would be required to fabricate the tank, assuming all sides and the bottoms are separate pieces? The top is open. Round answer to the nearest millimeter.__________________________________________________

c. Add dual dimensions to each of the welding symbols in U. S. Customary units.

e. How many cubic millimeters of weld are required?

d. What does the number 20 applied to the welding symbol signify?

19. a. In the following sketch, how many cubic millimeters of weld will be deposited on the surface to be welded? Round answer to nearest cubic millimeter.

b. On the sketch, show how the welded surface would appear in terms of “circumferential.”

c. List the U. S. Customary dimensions that may be added to the mm dimensions.

20. a. The base of the pyramid in the following sketch has equal sides. Its area measures 1452 square millimeters. How many millimeters of fillet weld are required around the base of the pyramid? Round answer to nearest millimeter.

21. Convert the answers to 20a., b., c., and d. to U. S. Customary units.

a. c.

b. .

d.

22. Convert the answers to questions 21a., b., c., and d. to U. S. Customary units.

b. d.

a. c.

b. How many cubic millimeters are contained in the pyramid? Round answer to the nearest cubic millimeter. The height of the pyramid is 127 millimeters.

Note: The formula for calculating the volume of a pyramid is as follows: 1/3 X area of base X height of pyramid = volume.

c. What is the length of the square groove weld for each of the edge joints of the pyramid? Round answer to the nearest millimeter.

Note: The formula for finding the hypotenuse of a triangle is as follows: height squared + base squared equals hypotenuse squared (a2 + b2 = c2).

d. How many cubic millimeters are contained in the rectangular member?

NOTE: DIMENSIONS ARE IN MILLIMETERS.

QUANT/ASSY	PART NO	DESCRIPTION	ITEM
2	2D743	CENTER SILL	1
			2
2	A4D343A	CENTER BRACE	3
2	A8D189	STRIKER	4
4	38B236B	SIDE REINFORCING	5
4	9B33	CENTER SILL SEPARATOR	6
3	9A34	CENTER SILL TIE STRAP	7
1	9A35	CENTER SILL SEPARATOR	8
4	38A262	HOPPER END CONNECTION	9

TYP >

<( TYP

v—<TVP

typ>TEJ-

TOP FLANGES TO BE BROUGHT FLUSH / & SQUARE BEFORE WELDING

THE BOTTOM OF THE CENTER BRACE IS TO BE FLUSH WITH THE BOTTOM OF THE CENTER SILL FLANGE PLUS 0.8 OUTSIDE, MINUS 0 INSIDE

SILLS MUST BE WATERPROOF AND HAVE A MINIMUM GROOVE WELD SIZE OF 60% OF THE JOINT THICKNESS, WITH AN ULTIMATE TENSILE STRENGTH ACROSS THE WELD OF 40,000 PSI. WHERE COVER PLATE, ETC., ARE TO BE APPLIED TO THE TOP SURFACE, THE WELD MUST BE GROUND SMOOTH. WHERE THE CENTER SILL SECTIONS ARE AUTOMATICALLY WELDED THE GROOVE WELD SIZE IS TO BE A MINIMUM OF 75%. AT BOLSTERS, THE GROOVE WELD SIZE IS TO BE 100% FOR A MINIMUM DISTANCE OF 609.6 ON EACH SIDE OF BOLSTER CENTER LINE.

NOTE: ALL DIMENSIONS ARE IN MILLIMETERS (mm) ROUNDED OFF TO ONE DECIMAL PLACE

CENTER SILL ASSEMBLY
REF. DWG. A2D664	PREPARED BY sae	CHECKED BY D. R.
CORRECT TV-______ -	APPROVED £T
SCALE 3/4" = 1 '-0"	DRAWING
DATE	A2D744

.2AT BOLSTER & END ELSE - +4-7' WHERE

A			ITEM 1 WAS 1 PER ASS'Y & ITEM 2 REMOVED
REV	BY	DATE	REVISION

EDITOR'S NOTE: REDUCED PRINT, FOLLOW STATED DIMENSIONS ONLY. NOT TO BE SCALED.

A LARGER DRAWING IS PROVIDED AT THE BACK OF THE TEXT.

UNIT 22: REVIEW B

Refer to the drawing, Center Sill Assembly, page 267. Graph paper is provided at the end of this review for your use.

1. Identify the views shown on the drawing. 2. Item ^ is identified as:

12. a. The bottom of item 3 is to be flush with the bottom of the____ . b. Describe the finish and method of finish required at the weld required to join the items in 14(a).

3. If automatic welding is carried out on the center sill, the penetration at the bolsters is to be_____________________________ %. 4. Describe the welds required to join item 5 to item 1.

13. What is the leg length in millimeters of the 5-mm fillet welds?

14. Describe the welds required to join the center sill separator to the center sill.

5. a. The total overall length of the assembled center sill in millimeters is____________________________________________

15. Describe the welds required at @ .

b. The tolerance allowed on the above dimension in millimeters is ____________________________________

6. The distance from corner ^ to corner © is

16. Describe the welds required at ©

7. Part #9A34 is known as, It is identified as item __

and the quantity required is_________________________________ 8. How many of item #9 are required for each assembly?

17. a. What is the size of the fillet welds to be applied as shown in Section A-A? b. What would this size be in inches?

9. How many center sill separators are required per assembly?

10. What is the length of item 1 in millimeters?

c. What is the contour specified for the fillet welds indicated in Section B-B?

11. What must the ultimate tensile strength be across the weld for the sills?