Screw and Clearance Hole
Screws are typically used for securing mating parts. When two pieces are joined together using screws, one piece is made with threads, and another piece is made with clearance holes, which have bigger diameters than that of the screws. If the diameter of the clearance hole is too small, the piece cannot be assembled as the screw will not fit through the hole. Also, if the diameter of the clearance hole is too big, , the piece will be loose as the hole will provide a sloppy fit. Therefore, we must provide make suitable diameter clearace holes. As a "rule of thumb", the diameter of the clearance hole has more 10 % than the diameter of the screw. For examples, the clearance hole for a M3 screw has 3.2 mm or 3.5 mm diameter. the clearance hole for a M4 screw has 4.2 mm or 4.5 of diameter. And we would make a hole with 5.5 mm of diameter for a M5 screw.
Thats one method.
What i do is
Close = dia + 1mm, ie: M6 = 7 dia hole
Normal = dia + 2mm ie M6 = 8 dia hole
Loose = dia + 3mm ie; M6 = 9 dia hole
this increases with large dia bolts
Daniel
Daniel
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