An M10 bolt has been selected for a reusable application. The proof stress of the low carbon steel bolt material is 310 MPa. Determine the recommended preload on the bolt and the torque setting.

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Accepted Answer

From Table 16.2,

Table 16.2: Selected dimensions for a selection of British Standard ISO Metric Precision Hexagon Bolts.

Nominal size and thread diameter	Pitch of thread (coarse pitch series)	Width across flats		Height of head		Tapping drill	Clearance drill
Nominal size and thread diameter	Pitch of thread (coarse pitch series)	(max)	(min)	(max)	(min)	Tapping drill	Clearance drill
M1.6	0.35	3.2	3.08	1.225	0.975	1.25	1.65
M2	0.4	4.0	3.88	1.525	1.275	1.60	2.05
M2.5	0.45	5.0	4.88	1.825	1.575	2.05	2.60
M3	0.5	5.5	5.38	2.125	1.875	2.50	3.10
M4	0.7	7.0	6.85	2.925	2.675	3.30	4.10
M5	0.8	8.0	7.85	3.650	3.35	4.20	5.10
M6	1	10.0	9.78	4.15	3.85	5.00	6.10
M8	1.25	13.0	12.73	5.65	5.35	6.80	8.20
M10	1.5	17.0	16.73	7.18	6.82	8.50	10.20
M12	1.75	19.0	18.67	8.18	7.82	10.20	12.20
M14	2	22.0	21.67	9.18	8.82	12.00	14.25
M16	2	24.0	23.67	10.18	9.82	14.00	16.25
M18	2.5	27.0	26.67	12.215	11.785	15.50	18.25
M20	2.5	30.0	29.67	13.215	12.785	17.50	20.25
M22	2.5	32.0	31.61	14.215	13.785	19.5	22.25
M24	3	36.0	35.38	15.215	14.785	21.00	24.25
M27	3	41.0	40.38	17.215	16.785	24.00	27.25
M30	3.5	46.0	45.38	19.26	18.74	26.50	30.50
M33	3.5	50.0	49.38	21.26	20.74	29.50	33.50
M36	4	55.0	54.26	23.26	22.74	32.00	36.50
M39	4	60.0	59.26	25.26	24.74	35.00	39.50
M42	4.5	65	64.26	26.26	25.74	37.50	42.50
M45	4.5	70.0	69.26	28.26	27.74	40.50	45.50
M48	5	75.0	74.26	30.26	29.74	43.00	48.75
M52	5	80.0	79.26	33.31	32.69	47.00	52.75
M56	5.5	85.0	84.13	35.31	34.69	50.50	56.75
M60	5.5	90.0	89.13	38.31	37.69	54.50	60.75
M64	6	95.0	94.13	40.31	39.69	58.00	64.75
M68	6	100.0	99.13	43.31	42.96	62.00	68.75

the pitch for a coarse series M10 bolt is 1.5 mm.

[latex]d_{p}=10-0.649519 imes 1.5=9.026 mm,[/latex]

[latex]d_{r}=10-1.226869 imes 1.5=8.160 mm,[/latex]

Table 16.5: Values for the constant K for determining the torque required to tighten a bolt.

Conditions	K
¼ in. to 1 in. mild steel bolts	0.2
Nonplated black finish steel bolts	0.3
Zinc-plated steel bolts	0.2
Lubricated steel bolts	0.18
Cadmium-plated steel bolts	0.16

[latex]A_{t}=\frac{\pi}{16}(9.026+8.16)^{2}=57.99 mm ^{2}[/latex]

For a reusable connection, the recommended preload is

[latex]F_{i}=0.75 A_{t} \sigma_{p}=13.48 kN[/latex].

From Table 16.5, K = 0.2.

The torque required to tighten the bolt is given by

[latex]T=K F_{i} d=0.2 imes 13.48 imes 10^{3} imes 0.01=26.96 N m[/latex]

Question 16.1: An M10 bolt has been selected for a reusable application. Th...

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