Washer (hardware)

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A washer is a thin plate (typically disk-shaped) with a hole (typically in the middle) that is normally used to distribute the load of a threaded fastener. Other uses are as a spacer, spring (belleville washer, wave washer), wear pad, preload indicating device, and locking device. Rubber or silicone washers may also be used to reduce vibration when fastening fans to computer cases. Washers usually have an outer diameter (OD) about twice the length of their inner diameter (ID).

Washers are usually metal or plastic. High quality capscrews require hardened steel washers to prevent the loss of pre-load due to Brinelling after the torque is applied. Rubber or fiber gaskets used in taps (or faucets, or valves) to stop the flow of water are sometimes referred to colloquially as washers; but, while they may look similar, washers and gaskets are usually designed for different functions and made differently.

Washers are also important for preventing galvanic corrosion, particularly by insulating steel screws from aluminum surfaces.

Contents 1 Types 1.1 Anchor 1.2 Belleville 1.3 Spherical 1.4 Torque 1.5 Washer nut 1.6 Other 2 Standard metric flat washers sizes 3 References 4 External links

[edit] Types

[edit] Anchor

An anchor plate or wall washer is a large plate or washer connected to a tie rod or bolt. Anchor plates are used on exterior walls of masonry buildings, for structural reinforcement. Being visible, many anchor plates are made in a style that is decorative.^[1]

[edit] Belleville

A Belleville washer, also known as a cupped spring washer, is a type of non-flat washer. It has a slight conical shape which gives the washer a spring characteristic. Belleville washers are typically used as springs, or to apply a pre-load or flexible quality to a bolted joint. Belleville springs are also used in a number of landmines e.g. the American M14 mine.

[edit] Spherical

A spherical washer is a washer with one radiused surface, which is designed to be used in conjunction with a mating nut in order to correct for up to several degrees of misalignment between parts.

[edit] Torque

A torque washer keeps the carriage bolt from spinning freely. It has a square hole in the center where the carriage bolt square fits into. It also has several bent prongs around the edge that dig into the wood to keep the washer from spinning.

[edit] Washer nut

The washer nut is a combination nut and washer. The washer is free floating just like using a separate washer and nut, however assembly is easier because the washer is captured.

[edit] Other

• bimetal
• bit guard (horse tack)
• crush washer
• fender washer (mudguard washer in UK; similar to repair washer)
• flat
• flat, hardened
• lock
• multi-tooth (star)
• phenolic
• shoulder
• split
• spring
• top hat
• wave

[edit] Standard metric flat washers sizes

Nominal screw sizes M (mm)		Screw pitch thread P (mm)		Internal (Inside) diameter hole d1 (mm)	External (Outside) diameter d2 (mm)	Height H (mm)
1st choice	2nd choice	coarse	fine
1		0.25		1.1	3	0.3
1.2		0.25		1.3	3.5	0.3
	1.4	0.3		1.5	4	0.3
1.6		0.35		1.7	4	0.3
	1.7			1.8	4.5	0.3
	1.8	0.35
2		0.4		2.2	5	0.3
2.5		0.45		2.7	6	0.5
	2.6			2.8	7	0.5
3		0.5		3.2	7	0.5
	3.5	0.6		3.7	8	0.5
4		0.7		4.3	9	0.8
5		0.8		5.3	10	1
6		1	0.75	6.4	12	1.6
	7	1		7.4	14	1.6
8		1.25	1	8.4	16	1.6
10		1.5	1.25 or 1	10.5	20	2
12		1.75	1.5 or 1.25	13	24	2.5
	14	2	1.5	15	28	2.5
16		2	1.5	17	30	3
	18	2.5	2 or 1.5	19	34	3
20		2.5	2 or 1.5	21	37	3
	22	2.5	2 or 1.5	23	39	3
24		3	2	25	44	4
	27	3	2	28	50	4
30		3.5	2	31	56	4
	33	3.5	2	34	60	5
36		4	3	37	66	5
	39	4	3	40	72	6
42		4.5	3	43	78	7
	45	4.5	3	46	85	7
48		5	3	50	92	8
	52	5	4	54	98	8
56		5.5	4	58	105	9
	60	5.5	4	62	110	9
64		6	4	66	115	9
	68			70	120	10
72				74	125	10
	76			78	135	10
80				82	140	12
	85			87	145	12
90				93	160	12
	100			104	175	14

[edit] References

[edit] External links

• The Straight Dope on lock washers