Socket head cap screws and counterbore holes are a matched made in heaven.

Socket head cap screws are widely used in precision engineering. They are particularly useful in applications where a higher torque is required or there is limited tool access but also, the cylindrical head with heaxagonal socket provides a more sophisticated look than standard hex bolts.

When using socket head cap screws, counterbore holes can be extremely useful in scenarios when:

• A clean appearance: is required: Counterbore holes are the perfect way to ensure protruding screw heads sit sub-flush to the surface
• Space constraints are tight and clearance above the mounting surface is limited
• Protection is required: To prevent damage to the screw head or to protect nearby components/personnel from sharp edges

Remember that counterbored holes reduce the effective thickness of the material, so always verify that the remaining material thickness is sufficient for your application’s load requirements.

Metric Fasteners

Fastener	Head Diameter	Head Height	C’Bore Diameter	Diameter Tolerance	Concentricity Tolerance*	C’Bore Depth**	Depth Tolerance**	Radius	Radius Tolerance
M3	5.50	3.00	7.10	+/-0.1	0.2	3.50	+/-0.1	0.5	+/-0.05
M4	7.00	4.00	8.60			4.50
M5	8.50	5.00	10.10			5.50
M6	10.00	6.00	11.60			6.50
M8	13.00	8.00	14.60			8.50
M10	16.00	10.00	17.60			10.50
M12	18.00	12.00	19.60			12.50

Imperial Fasteners

Fastener	Head Diameter	Head Height	C’Bore Diameter	Diameter Tolerance	Concentricity Tolerance*	C’Bore Depth**	Depth Tolerance**	Radius	Hole Radius Tolerance
#6	5.74	3.51	7.35	+/-0.1	0.2	4.00	+/-0.1	0.5	+/-0.05
#8	6.86	4.17	8.45			4.65
#10	7.92	4.83	9.50			5.35
1/4	9.53	6.35	11.15			6.85
5/16	11.91	7.94	13.50			8.45
3/8-	14.27	9.53	15.85			10.05
1/2	19.05	12.70	20.65			13.20

ELEVATE YOUR KNOWLEDGE

Check out the links to see:

• Example drawings
  See how this hole type should be displayed on manufacturing drawings