8.8Hex bolt(Nihon Fastener Kogyo(Coarse Steel Trivalent white(Silver) 6X25X18 Pitch 1.0

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This is a strength class 8.8 bolt with "8.8" stamped on the head.
It has a regular hexagonal head and is tightened using a wrench or spanner.
It can be tightened more securely than slotted or cross recessed screws.
●Full thread = A bolt where the entire length under the head is threaded. (Generally for lengths of 30mm or less)
●Partial thread (medium bolt) = A bolt that is only threaded from the tip partway up the shank.
Partial thread length calculation method (approximate guide)
〇L = up to 129　　　Thread diameter × 2 + 6　〇L = 130–219　　 Thread diameter × 2 + 12　〇L = 220 and above　　　　 Thread diameter × 2 + 25
Example: For an M10×250 partial thread bolt, since L (length) is 220 or more, the threaded length = 10×2+25 = 45mm.

●M30 × 80 and above will be partial thread.

Thread Pitch and Hex Width Across Flats List　Hex Bolt Encyclopedia

• 8.8 Hex bolt Nihon Fastener Kogyo Coarse pitch
• Nominal diameter (d) M6
• Pitch (P) 1.0
• Length under head (ℓ) 25.0
• Body diameter (ds) Nominal 6 Tolerance 0,-0.2
• Head height (k) Nominal 4 Tolerance ±0.25
• Width across flats (s) Nominal 10 Tolerance 0,-0.6
• Width across corners (e) Approx. 11.5
• Top surface diameter (dk) Approx. 9.8