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BS 939:2007 Engineers\\\' squares (including cylindrical and block squares). Specification, 2007
- Contents [Go to Page]
- Section 1: General 1
- 1 Scope 1
- 2 Normative references 1
- 3 Terms and definitions 1
- 4 Protection against climatic conditions 2
- Section 2: Engineers’ try squares 3
- 5 Designating size 3
- 6 Recommended sizes 3
- 7 Material and manufacture 4
- 8 General features of design 4
- 9 Finish 4
- 10 Accuracy 5
- 11 Rigidity 9
- 12 Marking 9
- Section 3: Cylindrical squares 10
- 13 Designating size 10
- 14 Recommended sizes and dimensions 10
- 15 Material and manufacture 11
- 16 General features of design 11
- 17 Finish 12
- 18 Accuracy 12
- 19 Marking 13
- Section 4: Solid form block squares 14
- 20 Designating size 14
- 21 Recommended sizes and dimensions 14
- 22 Material and manufacture 15
- 23 General features of design 15
- 24 Finish 16
- 25 Accuracy 16
- 26 Marking 17
- Section 5: Open form block squares 18
- 27 Designating size 18
- 28 Recommended sizes and dimensions 18
- 29 Material 19
- 30 General features of design 19
- 31 Finish 19
- 32 Accuracy 19
- 33 Marking 20
- Annexes
- Annex A (informative) Notes regarding bevelled edges on blades of grade AA engineers’ try squares 21
- Annex B (informative) Notes on the manufacture and testing of squares 25
- Bibliography 26
- List of figures
- Figure 1 - Exaggerated illustration of deviation from squareness and squareness tolerance 2
- Figure 2 - Engineers’ try squares 3
- Figure 3 - Squareness of blade edges to working faces of stock 8
- Figure 4 - Lateral squareness of blade 8
- Figure 5 - Rigidity 9
- Figure 6 - Nomenclature for cylindrical squares 10
- Figure 7 - Nomenclature for solid form block squares 14
- Figure 8 - Nomenclature for open form block squares 18
- Figure A.1 - Using a bevelled edge 21
- Figure B.1 - Method of testing squareness of block squares 23
- Figure B.2 - Tilting tester 24
- Figure B.3 - Testing for rigidity 25
- List of tables
- Table 1 - Tolerances on straightness of blade edges 5
- Table 2 - Tolerances on parallelism of blade edges 5
- Table 3 - Tolerances on flatness of working faces of stock 6
- Table 4 - Tolerances on parallelism of working faces of stock 6
- Table 5 - Tolerances on parallelism of side faces of stock 6
- Table 6 - Tolerances on squareness of blade edges to working faces of stock 7
- Table 7 - Tolerance on lateral squareness of blade to base of stock 8
- Table 8 - Recommended sizes and dimensions of cylindrical squares 10
- Table 9 - Tolerances on cylindrical squares 12
- Table 10 - Recommended sizes and dimensions of solid form block squares 14
- Table 11 - Tolerances on flatness, parallelism and squareness of working faces (solid iron block squares) 16
- Table 12 - Tolerances on flatness and squareness of front and back surfaces (solid iron block squares) 16
- Table 13 - Recommended sizes and dimensions of open form block squares 18
- Table 14 - Tolerances on flatness, parallelism and squareness of working faces (open form block squares) 20
- Table 15 - Tolerances on flatness and squareness of front and back surfaces (open form block squares) 20
- Foreword
- Section 1: General [Go to Page]
- 1 Scope
- 2 Normative references
- 3 Terms and definitions [Go to Page]
- 3.1 deviation from straightness and flatness
- 3.2 deviation from parallelism
- 3.3 Squareness of two surfaces [Go to Page]
- Figure 1 Exaggerated illustration of deviation from squareness and squareness tolerance
- 3.4 tolerances
- 4 Protection against climatic conditions
- Section 2: Engineers’ try squares [Go to Page]
- 5 Designating size [Go to Page]
- Figure 2 Engineers’ try squares
- 6 Recommended sizes
- 7 Material and manufacture
- 8 General features of design
- 9 Finish
- 10 Accuracy [Go to Page]
- 10.1 Straightness of inner and outer edges of blade [Go to Page]
- Table 1 Tolerances on straightness of blade edges
- 10.2 Parallelism of blade edges [Go to Page]
- Table 2 Tolerances on parallelism of blade edges
- 10.3 Flatness of working faces of stock [Go to Page]
- Table 3 Tolerances on flatness of working faces of stock
- 10.4 Parallelism of working faces of stock [Go to Page]
- Table 4 Tolerances on parallelism of working faces of stock
- 10.5 Parallelism of side faces of stock [Go to Page]
- Table 5 Tolerances on parallelism of side faces of stock
- 10.6 Squareness of side faces of stock to working faces of stock
- 10.7 Squareness of edges of blade to side faces of stock
- 10.8 Squareness of edges of blade to working faces of stock [Go to Page]
- a) the outer edge of the blade to the outer working face of the stock; and
- b) the inner edge of the blade to the inner working face of the stock; [Go to Page]
- Table 6 Tolerances on squareness of blade edges to working faces of stock
- Figure 3 Squareness of blade edges to working faces of stock
- 10.9 Lateral squareness of blade [Go to Page]
- Table 7 Tolerance on lateral squareness of blade to base of stock
- Figure 4 Lateral squareness of blade
- 11 Rigidity [Go to Page]
- Figure 5 Rigidity
- 12 Marking [Go to Page]
- a) the number of this British Standard, i.e. BS 939;
- b) the grade designation, e.g. A;
- c) an identification number for grade AA try squares; and
- d) the manufacturer’s name or trade mark.
- Section 3: Cylindrical squares [Go to Page]
- 13 Designating size [Go to Page]
- Figure 6 Nomenclature for cylindrical squares
- 14 Recommended sizes and dimensions [Go to Page]
- Table 8 Recommended sizes and dimensions of cylindrical squares
- 15 Material and manufacture [Go to Page]
- 15.1 Material
- 15.2 Steel squares
- 15.3 Cast iron squares
- 15.4 Granite (diabase) squares
- 16 General features of design
- 17 Finish
- 18 Accuracy [Go to Page]
- 18.1 General
- 18.2 Straightness of sides
- 18.3 Flatness of ends
- 18.4 Squareness of cylindrical surface to end faces [Go to Page]
- Table 9 Tolerances on cylindrical squares
- 19 Marking [Go to Page]
- a) the number of this British Standard, i.e. BS 939;
- b) the designating size and grade, e.g. 450 mm AA;
- c) an identification number;
- d) the manufacturer’s name or trade mark.
- Section 4: Solid form block squares [Go to Page]
- 20 Designating size [Go to Page]
- Figure 7 Nomenclature for solid form block squares
- 21 Recommended sizes and dimensions [Go to Page]
- Table 10 Recommended sizes and dimensions of solid form block squares
- 22 Material and manufacture [Go to Page]
- 22.1 Material
- 22.2 Steel squares
- 22.3 Cast iron squares
- 22.4 Granite (diabase) squares
- 23 General features of design
- 24 Finish
- 25 Accuracy [Go to Page]
- Table 11 Tolerances on flatness, parallelism and squareness of working faces (solid iron block squares)
- Table 12 Tolerances on flatness and squareness of front and back surfaces (solid iron block squares)
- 26 Marking [Go to Page]
- a) the number of this British Standard, i.e. BS 939;
- b) the designating size;
- c) the grade designation (AA or A, as appropriate);
- d) an identification number for grade AA squares;
- e) the manufacturer’s name or trade mark.
- Section 5: Open form block squares [Go to Page]
- 27 Designating size [Go to Page]
- Figure 8 Nomenclature for open form block squares
- 28 Recommended sizes and dimensions [Go to Page]
- Table 13 Recommended sizes and dimensions of open form block squares
- 29 Material
- 30 General features of design
- 31 Finish
- 32 Accuracy [Go to Page]
- 32.1 General
- 32.2 Open form block squares supplied in matched pairs [Go to Page]
- Table 14 Tolerances on flatness, parallelism and squareness of working faces (open form block squares)
- Table 15 Tolerances on flatness and squareness of front and back surfaces (open form block squares)
- 33 Marking [Go to Page]
- a) the number of this British Standard, i.e. BS 939;
- b) the designating size;
- c) the grade designation (A or B, as appropriate);
- d) an identification number;
- e) the manufacturer’s name or trade mark.
- Annex A (informative) Notes regarding bevelled edges on blades of grade AA engineers’ try squares [Go to Page]
- Figure A.1 Using a bevelled edge
- Annex B (informative) Notes on the manufacture and testing of squares [Go to Page]
- B.1 General [Go to Page]
- a) cylindrical and block squares;
- b) testing of engineers’ try squares; and
- c) the rigidity and design of engineers’ try squares.
- B.2 Cylindrical and block squares [Go to Page]
- B.2.1 General
- B.2.2 Cylindrical squares
- B.2.3 Block squares [Go to Page]
- Figure B.1 Method of testing squareness of block squares
- B.3 Engineers’ try squares [Go to Page]
- B.3.1 Testing an engineers’ try square against a reference cylindrical square or block square
- B.3.2 Tilting square-tester [Go to Page]
- Figure B.2 Tilting tester
- B.3.3 Rigidity of engineers’ try squares
- B.3.4 Notes on design of engineers’ try squares [Go to Page]
- Figure B.3 Testing for rigidity
- Bibliography [Go to Page]
- [1] National Physical Laboratory. Notes on Applied Science No. 5: Gauge Making and Measuring. London: HMSO, 1967. [Go to Page]