If used improperly, even the high strength classified bolts cannot guarantee the strength (tensile strength and etc.). In this vol., some basics (common sense level) of fastening using bolts will be explained.

(1) Combination of bolts and nuts

• The fastening strength guarantee values are for usages of bolts and nuts of the same strength classifications used in a normal manner.
• The term "used in a normal manner" means that all the threads of a standard thickness nut are fully engaged with the threads of a bolt ([Fig.1]).
• [Fig.2] shows examples of abnormal usages. The threads of the nuts are not utilized fully.
• [Fig.3] shows examples of excessively long incomplete threads and improper application of shoulder bolts. The subject to be fastened is not properly fastened with bolts and nuts.

(2) For a bolt and threads

• When bolting a part to a threaded part, the threads must be properly designed depending on the material strength of the threaded part.

Example

1. For low strength materials (i.e. aluminum), thread length must be made long in order to ensure ample thread strength.
2. If the thread length cannot be made sufficiently long, use threaded inserts (MISUMI: HLTS, etc.) for thread reinforcing.