1. Teknologi Dan Rekayasa
TECHNICAL DRAWING

2. SYMBOLS FOR SURFACE FINISH
Objective :
After studying this lesson, the students should be able to :
Explain the arrangement, type and meaning of surface symbols
Apply the surface finish symbols on technical drawing
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3. SYMBOLS FOR SURFACE FINISH
The use of symbols to denote surface finish (DIN / ISO 1302) supercedes the earlier conventional system of surface signs
Advantage :
More comprehensive and more accurate data can be entered in a very restricted space.
Denoting surface quality by :
Surface signs N8
Symbol
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4. SYMBOLS FOR SURFACE FINISH
Ground finish
N11 N5
Ground finish
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5. TYPES OF SYMBOLS
The basic symbol consists of two straight lines of different lengths inclined at 60° to the reference surface.
There are three types of symbol :
1. Basic symbol on reference surface
2. Basic symbol with circle
3. Basic symbol with transverse line
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6. 1. Basic symbol on reference surface
as group symbol
60° 10 5
60°
6-7
3 - 3,5
on the right above the elevation
The thickness of the line is 1/10 of the height of the smaller leg. This basic symbol acquires its meaning solely when used in combination with a descriptive word
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7. 1. Basic symbol on reference surface
painted grey
sand blasted
When such a descriptive word is used a horizontal line is added to the longer leg
NOTE :
Descriptive words are always written horizontally
The description always denotes the final condition
Example :
milled do not mill driled - do not drilled
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8. 2. Basic symbol with circle
For chipless forming, i.e. cast, forged, rolled, etc, a circle is added to the basic symbol
hardened
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9. 3. Basic symbol with transverse line
For a machined surface, for example, shaped, milled, turned, drilled, reamed and fillet etc, a transverse line is added to the basic symbol.
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10. LAY OUT OF DATA
For a machined surface, for example, shaped, milled, turned, drilled, reamed and fillet, etc, a transverse line is added to the basic symbol.
= roughness number (N1 – N12) or degree of roughness (Ra) in um (1/1000 mm)
= manufacturing process, treatment surface coating
= test length in mm
= direction of machining grooves
= machining allowance in mm
= additional roughness values (Rt, Rz, etc) a e d b
c / f
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11. a = roughness number (N1 – N12) or degree of roughness (Ra) in um (1/1000 mm)
Example : N5
new
previous
new
previous

12. b = manufacturing process, treatment surface coating
Information relating to a particular manufacturing process, treatment or surface coating can be given on the extension line
Information relating to surface treatment (hardness data) is entered on a thick chain doted line just above the surface to be treated
Example : N6
point hardened N5
ground
case hardened N7
painted grey

13. c = test length in mm / additional roughness data in
The test length and the depth of roughness are only rarely specified in practice
Example : N8
2,5 / Ra=3,2
2,5 / Ra=1,6 N7
Ra = depth of roughness

14. d = machining grooves direction (on the right next to the symbol)
The following symbols indicate the general direction of the machining grooves
= : parallel to the plane of projection
丄 : perpendicular to the plane of projection
X : crossing (cross line)
M, C, R (for explanation see standard)
These symbols should only be entered when they are necessary for the functioning of the component. The explanation of these symbols may be obtained, as required, from the standard (DIN / ISO 1302)

15. d = machining grooves direction (on the right next to the symbol)
Example :
direction of groove

16. e = machining allowance
Where necessary, a value should be specified for the machining allowance (i.e. for sub sequent grinding), this is to be indicated on the left hand side of the symbol
Example : N6
Hardened and ground
0,2
ground N5
0,5

17. STANDARD PROCEDURE
The symbol and lettering must be arranged so that they can be read from the bottom and from the right
The symbol must only be entered once for a given surface and at the point where the particular surface is dimensioned Ø

18. STANDARD PROCEDURE
If necessary, the symbol can be connected by a line with an arrow Ø

19. STANDARD PROCEDURE
If the component is to have the same surface finish on all sides, the a group symbol must be placed on the right above the front view, following the part number
The words “on all sides” can be added
on all sides a 1
thus or

20. STANDARD PROCEDURE
If the same surface quality is to be provided on most of the surfaces of a workpiece, this must be specified as group symbols above the view. All additional symbols relating to the workpiece should be entered on the workpiece, and must be specified in one of the following ways beside the group symbol.

21. 3 1 STANDARD PROCEDURE Variant 1.
Is preferable because it requires the least work (economical)

22. STANDARD PROCEDURE
Variant 2.
Gives greater detail 2 a1 3 a2 a3

23. STANDARD PROCEDURE 3 a1 a2 a3
Variant 3.
Is very involved

24. THE END
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