Washers under nuts

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I would say yes but it can sometimes be difficult to get the correct scale size for a model unless you make your own.

Brian

Usually yes; unless you use flanged nuts.

Geo.

.

No ... Sometimes the nut is captive [in a suitably shaped recess] and the washer is then much more useful under the head of the bolt.

MichaelG.

No; in the photos I have of full size Burrell SCC traction engines almost none of the nuts have washers underneath them.

Andrew

no. but they stop your paint from damage when tightening up.

Under which bit rotates, we were told and I've stuck with it. John

There are some circumstances ahere a washer should NOT be used. For example, if both the bolt and the surface it's fitted to are hardened an normal soft washer will reduce the reliability.

Russell

Certainly if material being fixed is likely to be damaged by the nut, damage can be reduced if the hex is turned off at the point of contact but I prefer a washer to spread the load.

Emgee

Should washers ALWAYS ? be fitted under nuts or not?

Simple answer to the OP’s simple question is No.

Hi Russell, but you can get hardened washers.

Generally, you don't have to have any washers at all, if you don't want them, but if you are bolting a thin sheet to a thicker section it would be advisable to have a washer in most cases, on top of the thin sheet, whether it's the head of the bolt or the nut. Personally, I like to have them under both head and nut in most situations where it is possible. In structural steelwork it is common to see them on both sides, as the holes are very often bigger, mainly for easy erection and small adjustments.

Regards Nick.

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I'd rather be wrong than wright.

Andrew

I'd rather be wright than wrong.

Pat

Do two Wrights make a Wrong?🙂

No. Two wright's made 3 more wright's.

Pat

Hi, well that should be all wright then! right! or is that wrong also.

Regards Nick.

Personally I tend to use washers most of the time for stuff I'm making, just feel they give a better 'fit' to things. If you study the vast majority of early industrial / victorian engineering they never seemed to use them. Was this because of the extra cost or just considered unecessary? When did they start to become in regular use, and was it one of these trends that started perhaps in America and spread over here or vice versa? Have often wondered. Regards

I'd rather chew up a sacrificial component than a spotface, and I'd rather spread the compressive load there and at the bolt end as well, so my default position is to use them at both ends.

Unless otherwise prompted by other tech considerations, shortage or laziness.

Intrigued by the why washers question I went through my collection of Engineering Books in hope of finding an explanation. Nope! Instead I found inconsistencies. Drawings sometimes show washers and sometimes not. There's a British Standard covering metric washers but it concerns itself only with dimensions. BS metric washer can be made of almost anything ranging from plastic to hardened steel. Brass and mild-steel seem popular.

None of my books explain anything, but I suggest 6 reasons for fitting plain washers:

• To spread the load so the nut doesn't crush a soft material, or have the sharp edges cut into it as the nut is tightened.
• To avoid the nut damaging painted or plated surfaces put on to protect the underlying metal against corrosion.
• For cosmetic reasons - looks neater, and keeps paintwork safe.
• To bridge gaps when the hole is larger than the bolt, as when fixing a panel through holes slotted to simplify fitting. (No need for the holes to be accurately positioned - the washer covers up a wide tolerance.)
• To grip something that might otherwise be squeezed out at the nut rotates, such as a wire in a screw terminal.
• By provide two bearing surfaces, the washer reduces friction as the nut is tightened, making an ordinary spanner slightly more effective. The nut is tighter, and the bolt tensioned better.

Another mystery my books don't answer is thread angles. Metric and American bolts are both 60°, Whitworth is 55°, Lowenherz 53.1333°, and Thury and BA are 47.5°. Just guessing, but within the range of practical thread angles I think 60° provides the strongest thread, whilst the weaker 47.5° angle provides higher friction and is less likely to come undone. Does anyone know the actual answer?

Dave