Guide 09 · Fastener Reference Guide

High Tensile Bolts

ISO metric precision hex bolts and set screws — dimensions and properties.

In Australian steel construction a bolt is specified by two things: its property class, and how it is installed. That is what the bolting categories in AS 4100 describe — the letter after the slash is the installation method, not a different bolt.

The four categories

4.6/S — commercial bolts to AS/NZS 1111, property class 4.6, tightened with a standard wrench to snug tight.
8.8/S — any property class 8.8 bolt, snug tightened the same way. Effectively a higher grade commercial bolt, used to lift the capacity of the connection.
8.8/TF — high strength structural bolts to AS/NZS 1252, fully tensioned, in a friction-type joint. The clamped plates carry the load through friction and the joint does not slip.
8.8/TB — the same fully tensioned AS/NZS 1252 assembly in a bearing-type joint, where the design allows the connection to bear on the bolts.

As a rule of thumb, 4.6/S and 8.8/S are used in simple (flexible) connections, while 8.8/TB is the most common procedure in rigid connections in Australia.

Snug tight is not "as tight as it will go"

Snug tight means firm contact between the plies — the effort of one person on a standard wrench. Full tensioning is a different operation altogether: the bolt is deliberately stretched to a specified minimum tension by a controlled method such as part-turn, load-indicating washers or a calibrated tool.

If a drawing calls for /TF or /TB, simply tightening the bolts hard does not deliver the design capacity, and there is no way to tell by looking. The installation method is part of the specification.

Fully tensioned assemblies also need the right hardened washers. Under a tensioned high strength bolt an ordinary washer can dish or bite into the steel, and the tension you carefully applied disappears into that deformation.

High Tensile Bolts — page 1 of the MEGAFIX Fastener Reference Guide

Text version — searchable and screen-reader friendly

Bolts Set Screws AS 1110.1

Diameter mm	Pitch mm	af	af	ac	ac	h	h	ds	ds	t	t	t
		Min	Max	Min	Min	Max	Min	Max	L ≤ 125	125 < L ≤ 200	L > 200
M4	0.70	6.78	7.00	7.66	2.68	2.92	3.82	4.00	14	20	33	7
M5	0.80	7.78	8.00	8.79	3.35	3.65	4.82	5.00	16	22	35	8
M6	1.00	9.78	10.00	11.05	3.85	4.15	5.82	6.00	18	24	37	10
M8	1.25	12.73	13.00	14.38	5.15	5.45	7.78	8.00	22	28	41	13
M10	1.50	15.73	16.00	17.77	6.22	6.58	9.78	10.00	26	32	45	16
M12	1.75	17.73	18.00	20.03	7.32	7.68	11.73	12.00	30	36	49	18
M14	2.00	20.67	21.00	23.36	8.62	8.98	13.73	14.00	34	40	53	21
M16	2.00	23.67	24.00	26.75	9.82	10.18	15.73	16.00	38	44	57	24
M18	2.50	26.67	27.00	30.14	11.28	11.72	17.73	18.00	42	48	61	27
M20	2.50	29.67	30.00	33.53	12.28	12.72	19.67	20.00	46	52	65	30
M22	2.50	33.38	34.00	37.72	13.78	14.22	21.67	22.00	50	56	69	34
M24	3.00	35.38	36.00	39.98	14.78	15.22	23.67	24.00	54	60	73	36
M27	3.00	40.00	41.00	45.20	16.35	17.35	26.48	27.00	60	66	79	41
M30	3.50	45.00	46.00	50.85	18.28	19.12	29.48	30.00	66	72	85	46
M33	3.50	49.00	50.00	55.37	20.58	21.42	32.38	33.00	–	78	91	50
M36	4.00	53.80	55.00	60.79	22.08	22.92	35.38	36.00	–	84	97	55
M42	4.50	63.10	65.00	71.30	25.58	26.42	41.38	42.00	–	96	109	65
M48	5.00	73.10	75.00	82.60	29.58	30.42	47.38	48.00	–	108	121	75
M56	5.50	82.80	85.00	93.56	34.50	35.50	55.26	56.00	–	–	137	85
M64	6.00	92.80	95.00	104.86	39.50	40.50	63.26	64.00	–	–	153	95

Property Class 8.8 and 10.9 Bolts Set Screws AS 1110.1

Diameter mm	Pitch mm	af	af	ac	ac	h	h	ds	ds	t	t	t
		Min	Max	Min	Min	Max	Min	Max	L ≤ 125	125 < L ≤ 200	L > 200
M8	1.00	12.73	13.00	14.38	5.15	5.45	7.78	8.00	22	28	41	13
M10	1.00/1.25	15.73	16.00	17.77	6.22	6.58	9.78	10.00	26	32	45	16
M12	1.25/1.50	17.73	18.00	20.03	7.32	7.68	11.73	12.00	30	36	49	18
M14	1.50	20.67	21.00	23.36	8.62	8.98	13.73	14.00	34	40	53	21
M16	1.50	23.67	24.00	26.75	9.82	10.18	15.73	16.00	38	44	57	24
M18	1.50	26.67	27.00	30.14	11.28	11.72	17.73	18.00	42	48	61	27
M20	1.50	29.67	30.00	33.53	12.28	12.72	19.67	20.00	46	52	65	30
M24	2.00	35.38	36.00	39.98	14.78	15.22	23.67	24.00	54	60	73	36

UNC and UNF Grade 5 and 8 AS/NZS 2465

Diameter	Pitch (UNC)	Pitch (UNF)	af (Min)	af (Max)	ac (Min)	ac (Max)	h (Min)	h (Max)	ds (Min)	ds (Max)	t (Min)
1/4	20	28	0.428	0.438	0.488	0.505	0.150	0.163	0.245	0.250	3/4
5/16	18	24	0.489	0.500	0.557	0.577	0.195	0.211	0.306	0.313	7/8
3/8	16	24	0.551	0.562	0.628	0.650	0.226	0.243	0.369	0.375	1
7/16	14	20	0.612	0.625	0.698	0.722	0.272	0.291	0.430	0.438	1 1/8
1/2	13	20	0.736	0.750	0.840	0.866	0.302	0.323	0.493	0.500	1 1/4
9/16	12	18	0.798	0.812	0.910	0.938	0.348	0.371	0.554	0.563	1 3/8
5/8	11	18	0.922	0.938	1.051	1.083	0.378	0.403	0.617	0.625	1 1/2
3/4	10	16	1.100	1.125	1.245	1.299	0.455	0.483	0.741	0.750	1 3/4
7/8	9	14	1.285	1.312	1.461	1.516	0.531	0.563	0.866	0.875	2
1	8	12	1.469	1.500	1.675	1.732	0.591	0.627	0.990	1.000	2 1/4
1 1/8	7	12	1.631	1.688	1.859	1.949	0.658	0.718	1.114	1.125	2 1/2
1 1/4	7	12	1.812	1.875	2.066	2.165	0.749	0.813	1.239	1.250	2 3/4
1 3/8	6	12	1.994	2.062	2.273	2.382	0.810	0.878	1.363	1.375	3
1 1/2	6	12	2.175	2.250	2.480	2.598	0.902	0.974	1.488	1.500	3 1/4

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