小形二面幅をもつスタイル１超軽量フランジ付き六角ナットの締付け特性

抄録

Hexagon nuts with flange are widely used as fastening components for their high loadability on the mating threads and on the bearing face. However, it was pointed out that the actual mechanical properties of nuts with flange specified in JIS B 1190 are excessive compared with the bolts mated since the flange boosts the stiffness against the nut dilation. Furthermore, the width across flats specified in the current product standard is bigger (e.g., s=13 mm for M8) than that of bolts mated (e.g., s=10 mm for M8). This may bring some troubles in assembly and may reduce the assemblability (workability). Therefore in the Japanese automotive industry, they have their own product standards (JASO F 126 and F 127) in which the common width across flats (e.g., s=12 mm for M8) is specified for bolts and nuts.

This study aims to develop the lighter weight (critical design) nuts with flange by reducing both the width across flats and the nut height. In this paper, as one of the extreme cases, the tightening characteristics of M8 hexagon nut with flange having the width across flats s of 10 mm with style 1 nut height was compared with those of regular hexagon nuts with flange (s=13 mm) of the same material and manufacturing procedures.

It was confirmed through tensile test that this super light weight hexagon nuts with flange with 230HV have equivalent loadability of property class 10 style 1 hexagon nuts with 270HV (min). The results from the loadability test for the driving feature and the tightening test show that the super light weight nuts quenched and tempered can be used in combination with a bolt of property class 10.9.