Wrench / spanner clearances around screw Heads

Wrench / spanner clearances around screw Heads

Important Note

The information below is generally based on conservative appraisals of the clearance required for open ended spanners, ring spanners, and sockets. It is probable that smaller dimensions can be used if the wrench / spanner / socket geometry is selected at the early design stage.    The links on this table provide more detailed information.

For Bolt edge distances applicable to structural design refer to Edge Distances

Bolts Holes, Min Spacings, and Wrench / Spanner Clearances Precision Hexagon Bolts And Screws

Dimensions in mm

Tables for bolts and screws in accordance with BS 3692:2001..ISO metric precision hexagon bolts, screws and nuts. Specification.

Note clearance hole dimension "D" is in line with BS EN 20273:1992, ISO 273:1979. med fit

Size	Hole D	Min P	Clearance			G	S Nom. Size Spanner(A/F)	H (Sq.Drive)
			a	b	c
M3	3.4	14	10	8	10	-	5.5	14(6,3)
M4	4.5	17	10	8	12	14	7	22(10)
M5	5.5	20	10	8	12	14	8	22(10)
M6	6.6	24	14	10	15	17	10	26(12,5)
M8	9.0	30	18	12	18	22	13	26(12,5)
M10	11.0	37	28	14	21	27	17	27(12,5)
M12	13.5	42	30	16	22	30	19	29(12,5)
M16	17.5	50	30	20	26	38	24	42(20)
M20	22,0	60	32	22	32	46	30	47(20)
M24	26,0	75	48	25	38	55	36	54(20)
M30	33.0	94	60	30	48	70	46	70(25)
M36	39.0	104	60	34	52	90	55	81(25)

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High Strength Friction Grip Bolts

Dimensions in mm

Clearances suitable for bolts & nuts to BS EN 14399-3:2005.. High-strength structural bolting for preloading. System HR. Hexagon bolt and nut

Size	Min P	Clearance			G	S Nom. Size Spanner (A/F)
		a	b	c
M16	56	30	25	38	27	27
M20	64	48	28	42	48	32
M24	84	48	40	55	65	41
M30	98	60	45	65	77	50
M36	112	60	45	70	81	60

Relevant links

1. Tecnocentro Wrench clearances.. Excellent source of relevant information - Better and more detailed than my information
2. EngineersEdge Wrench Clearances.. American (inch sizes) similar to Information in Machinerys Handbook
3. Icrank Wrench Clearances.. American (inch sizes) .