Hex socket head cap screw(Coarse Steel Unplated 8 X 25(P=1.25 Pitch 1.25

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This is a bolt with a cylindrical head featuring a hexagonal socket.
Tightening is performed using a hex key (Allen wrench). Although classified as a bolt, it is most commonly used without a nut.
It is also known as a cap screw or socket screw.
Spanners and wrenches with jaws for tightening hex bolts require clearance space around the work area, whereas a hex key requires no such space.
For this reason, hex socket head cap screws enable work in confined spaces and allow for more compact machine designs.
Their appearance has also led to increasing use in decorative applications.


Cap Bolts　
Representative Standard Dimensions for CAP Screws　
Hex Socket Head Cap Screws　

• Hex socket head cap screw (Coarse pitch)
• Nominal diameter (d) M8
• Length under head (ℓ) 25.0
• Pitch (P) 1.25
• Thread length (b) Reference 28
• Head diameter (dk) Max(1) Nominal 13 Max(2) 13.27 Min 12.73
• Neck diameter (da) Max 9.2
• Body diameter (ds) Max Nominal 8 Min 7.78
• Hex socket width across corners (e) Min 6.863
• Head height (k) Max Nominal 8 Min 7.64
• Neck fillet (r) Min 0.4
• Hex socket width across flats (s) Nominal Nominal 6 Max 6.14 Min 6.02
• Hex socket depth (t) Min 4
• Head chamfer (v) Max 0.8
• *Max(1) Maximum diameter without knurling / Max(2) Maximum diameter with knurling