Hex socket head cap screw P=3(Coarse Stainless steel Unplated 8 X 20 Pitch 1.25

This is a bolt with a hexagonal socket in a cylindrical head. Tightening is performed using a hex key (Allen wrench).
In most cases, it is used without a nut. It is also known as a cap screw or socket screw.
When fastening a hex bolt, a wrench requires working space, whereas a hex key does not.

Cap Bolt　
Hex Socket Head Cap Screw Encyclopedia
Cap Bolt　P=3

• Hex socket head cap screw P=3 Coarse pitch
• P=3 (With spring washer + JIS flat washer)
• Nominal thread diameter M8
• Length under head (L) 20.0
• Coarse pitch 1.25
• Head diameter (dk) Nominal 13 Max 13.27 Min 12.73
• Head height (k) Nominal 8 Min 7.64
• Hex socket width across flats (s) Nominal 6 Max 6.14 Min 6.02
• Hex socket depth (t) Min 4
• Flat washer (D x t) 18 x 1.6
• Spring washer (d) Max 14.3
• Spring washer (b x t) 3.2 x 2.0
• Incomplete thread length Max 7.7
• Partial thread range L55 or more
• Partial thread thread length 40 - 44
• *Full thread thread length = L dimension - Incomplete thread length