Machinery's Handbook, 31st Edition
1790 Miniature Screws End of Body: Miniature fastening screws shall be regularly supplied with flat ends hav ing a chamfer of approximately 45° extending to the minor diameter of the thread as a minimum depth. Thread Series and Tolerances: The screw threads of miniature screws shall be in confor mance with American Standard Unified Miniature Screw Threads, ASA B1.10-1958. Material and Finish: Miniature screws are generally supplied in ferrous and nonferrous materials, coatings, and heat treatments which must be specified by the user. Coatings, when required, are limited to those of electro-plating or chemical oxidation. Designation: Screws in conformance with this standard shall be identified by the desig nation for thread size in conformance with American Standard ASA B1.10 followed by the nominal length in units of 1 ∕ 1000 inch (omitting the decimal point) and the head type. Typical examples are: 60 UNM × 040 FIL HD
100 UNM × 080 PAN HD 120 UNM × 120 FLAT HD 140 UNM × 250 BIND HD
Machined Finish: Roughness of the machined surfaces of heads shall not exceed 63 micro-inches arithmetical average (per ASA B46.1, Surface Texture) determined by visual comparison with roughness comparison specimens. American National Standard Metric Machine Screws This Standard B18.6.7M (Withdrawn) covers metric flat and oval countersunk and slot - ted and recessed pan head machine screws and metric hex head and hex flange head ma - chine screws. Dimensions are given in Table 1 through Table 4 and Table 5. Threads: Threads for metric machine screws are coarse M profile threads, as given in ANSI/ASME B1.13M (see page 2012 ), unless otherwise specified. Length of Thread: The lengths of threads on metric machine screws are given in Table 1 for the applicable screw type, size, and length. Also see Table 6. Diameter of Body: The body diameters of metric machine screws are within the limits specified in the dimensional tables ( Table 3 through Table 4 and Table 5 ). Designation: Metric machine screws are designated by the following data in the sequence shown: Nominal size and thread pitch; nominal length; product name, including head type and driving provision; header point if desired; material (including property class, if steel); and protective finish, if required. For example: M8 × 1.25 × 30 Slotted Pan Head Machine Screw, Class 4.8 Steel, Zinc Plated M3.5 × 0.6 × 20 Type IA Cross Recessed Oval Countersunk Head Machine Screw, Header Point, Brass It is common ISO practice to omit the thread pitch from the product size designation when screw threads are the metric coarse thread series, e.g., M10 stands for M10 × 1.5.
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