Washers under nuts

[JAParticipant @ja]

Posted by SillyOldDuffer on 30/01/2021 12:12:28:

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

 

Dave

Wrong way round. The 60degrees thread is the weakest and less likely to un-do. The thread is a double wedge, a small pitch and large thread angle will give a small angle wedge. Hence the use of 60degrees and 26tpi used on cycle threads. It also suggests that BA screws would be frequently undone and done up.

As for washers, generally they have been used under nuts for at least 170 years. Before then washers were difficult to make and not used. There are no washer on the Pontcycslite aqueduct. I worked with jet engines where each set of flanges were held together with 100s of flanged screws and nuts (without washers). I don't think washers were used with larger, ordinary, nuts used in the core of the engine.

As for models, this is simple. If the model is "generic", such as a Stuart 10, use washers. If it is of an actual full size engine etc, copy the full size. If it is your own design you can make the rules (but you should stick to them).

JA

The thread answer suggests that lab technicians would be cack-handed and motorcyclists very careful with spanners.

 

Edited By JA on 30/01/2021 13:19:15

Edited By JA on 30/01/2021 13:20:05

[Ian Johnson 1Participant @ianjohnson1]

I remember one of the F1 team engineers, may have been team McLaren? He said he didn't use washers on the cars because he didn't see why they should get a free ride around the race track. In other words washers are not an essential component.

IanJ

[S.D.L.Participant @s-d-l]

Posted by Mike Hurley on 30/01/2021 11:18:36:

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 suspect that washers every where came from working on costs plus jobs for the MOD in the cold war where if you added washers everywhere on thousands of bits of kit and got cost plus profit it would add up.

Reason for this is everyone iIhave met that worked for GEC, Marconi, BAC etc wants washers every where, and when asked why because there supervisor or manager insisted, never have got a good explanation.

Commercial people I have worked with only wanted them if to cover slots or protect paint etc.

Steve

[JAParticipant @ja]

Posted by not done it yet on 30/01/2021 13:21:14:

The whole thread smacks of little initial thought, or just posting for something to do.

What do you expect with a freezing workshop and bitterly cold high winds and rain from the east.

JA

[Former MemberParticipant @formermember12892]

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[Former MemberParticipant @formermember12892]

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[JAParticipant @ja]

br

I should not really reply to this.

There is nothing at all wrong with your question and after some consideration I tried to give a sensible reply to it and Dave's comments. I DO NOT consider it a beginner's question at all. Everyone is still learning, I hope.

My comment on the weather was due to the sort of trivial replies that had been posted.

JA

[Brian HParticipant @brianh50089]

I thought that this was an excellent question to ask. I've always thought that a washer should be used but note from some of the replies that this may not be the case.

My 'go to' book is a text book for draughtsmen dated 1880 and shows various engineering items and assemblies with instructions as to how they should be drawn.

It shows washers being used in some assemblies but not in others, so no answer there then. I would still tend to use washers unless there was a specific reason not to.

Brian

[Tim StevensParticipant @timstevens64731]

I suggest that the reasons for differing angles on early thread systems were not recorded when they were 'invented'. Very likely the earliest threads in use were made by craftsmen working by eye, and very often in wood rather than metal. As soon as there was a need for lots of threaded parts, and interchangeability was the aim, attempts would have been made to set 'standards' for each workshop. When it became obvious that general standards would be an even better idea, the threads were standardised on what was in use most generally at the time – and using the dimensions system of the area, or the trade, involved. So, steam engines made in Newcastle on Tyne used inches and sixteenths for bolts and threads, and then Whitworth came along and copied the flank angles they used for his thread standards – generally around 55 degrees. Engineers in France would be likely to use the metric system as soon as it was created (just in time, really), Germany used Whitworth or Metric depending on designer whims, or availability of tooling, or whatever. Later when electrical work was done the standard preferred for small stuff for switches and domestic fittings was BA, set out by the British Association at the request of electrical engineers, not according to previous good practice but on theoretical principles of proportion. Specialist trades like clock and watch making, and sewing machines, also developed their own thread systems, to meet their own specialised needs.

And every trade seems to have had odd special sizes – such as the 9/32" x 26tpi BSF thread just used for bicycle pedal cotters, and the German 68mm and 82mm threads for Honey Pots only.

Spanner sizes are a further area for confusion, irritation, or enthusiasm.

Cheers, Tim

[Tim StevensParticipant @timstevens64731]

I was forgetting – long ago I was talking about washers with engineers at Land Rover. Their explanation for 'shakeproof' washers (the ones with radial blades twisted like micro-propellors) – was 'Oh, those. They are designed so that the rain water gets into the threads and locks everything together properly.'

Cheers, Tim

[John ShepherdParticipant @johnshepherd38883]

Mick B1 – A question I have wanted to ask for some time. Thanks for raising it.

From the answers given, I think I will base my use of washers as follows:

1. Under the part that rotates
2. To protect a surface
3. If I want to spread the load I will use a large washer not a standard size one
4. It looks right
5. I won't beat myself up if I don't fit one

I saw a chalk drawing on the wall of a factory some years ago that showed a machine screw with legs chasing a nut also with legs and the caption was "not without a washer"

[Neil WyattModerator @neilwyatt]

Posted by br on 29/01/2021 15:07:06:

Should washers ALWAYS ? be fitted under nuts ?

Thanks

br

Simply put, no not always.

Most nuts on cars or steam engine don't use washers.

I remember a piece in ME claiming washers were never used on prototype steam engines, ironically the one pictured on the cover had washers…

To protect paint nuts can be fitted bevel edge down.

Neil

[Neil WyattModerator @neilwyatt]

Posted by JA on 30/01/2021 13:12:43:

As for models, this is simple. If the model is "generic", such as a Stuart 10, use washers. If it is of an actual full size engine etc, copy the full size. If it is your own design you can make the rules (but you should stick to them).

Stuarts never specified washers!

They are very rarely used on prototype steam engines and where do you see them on cars – only where there is a specific need for them.

Random washers for appearance’s sake on engineering models are like brass belaying pins on model sailing ships (ugh!!)

Rant over!

Neil

[Neil WyattModerator @neilwyatt]

Posted by S.D.L. on 30/01/2021 13:21:34:

Reason for this is everyone iIhave met that worked for GEC, Marconi, BAC etc wants washers every where, and when asked why because there supervisor or manager insisted, never have got a good explanation.

Because they are electronic engineers not mechanical engineers

Neil

[Former MemberParticipant @formermember12892]

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[JasonBModerator @jasonb]

Answer to the original question is YES, as they don't do a lot when fitted above the nut

[Former MemberParticipant @formermember12892]

[This posting has been removed]

[JAParticipant @ja]

Just had a look at my Stuart 7 that I finished quite a few years ago. There are no washers.

(There should be a "smiley" of a head being hit with a hammer)

JA

[JasonBModerator @jasonb]

Will these do?

Edited By JasonB on 30/01/2021 17:14:35

[JAParticipant @ja]

Thanks JasonB.

I have just looked back at Hick, Hargreaves & Co drawings and photographs from the Engineer between 1850 and 1950. Washers were used on some engines and not others. Some engines had washers under only some nuts, and so on.

I am leaving this posting totally confused. I shall return to trying to understand the Stephenson's reversing gear.

JA

Edited By JA on 30/01/2021 17:29:01

Edited By JA on 30/01/2021 17:30:42

[HOWARDTParticipant @howardt]

An interesting article here Bolt science. There are no doubt lots of other papers as it is a science in its self. For the modeller though much of it is for aesthetic reason like hexagon size on bolts.

[Anonymous]

Posted by Neil Wyatt on 30/01/2021 16:45:42:

Because they are electronic engineers not mechanical engineers

… but mechanical engineering is "obvious"; anyone can do it. Ask any electrical/electronics engineer.

[Brian HParticipant @brianh50089]

You wouldn't believe that a simple question could generate so many answers, which goes to show that the question was a very valid one.

Brian

[Michael GilliganParticipant @michaelgilligan61133]

Posted by not done it yet on 30/01/2021 13:21:14:

[…]

Does nobody use spring washers these days?

The whole thread smacks of little initial thought, or just posting for something to do.

.

If answering that question in your style … NO
 

[ noting that your unfortunate phrasing does smack of little initial thought, or just posting for something to do ]

MichaelG.

.

Some people do use spring washers, therefore nobody doesn’t

 

 

Edited By Michael Gilligan on 31/01/2021 10:21:45

[Nigel McBurney 1Participant @nigelmcburney1]

design and production engineers do not like washers and avoid their use,its another part number,which has a cost,an assembler can miss a washer then it becomes a quality problem ,or they can be all to easily dropped into an assembly incurring delays and costs ,if washers are required modern preference is to have captive washers supplied pre assembled to the screw or bolt,this was usual practice on hard drives in my time,to prevent microscopic particles of aluminium being generated,which can be the death knell of a hard drive. Washers are used where a part has a slotted hole or quadrant for adjustment purposes. back in the days when cast iron was the most common material and hole drilling was slow and laborious,holes which did not need to be accurate were often cast to an approximate size which cost nothing,eg holes in engine and machine tool bases,to secure them to a floor or other mounting where the hole was often far larger than the bolt and a hefty washer was required. Where there is a variation in the use of washers or no washers on similar types of machinery its very often due to the preference of the owner or other senior member of a manufacturing company whos word was not questioned particularly in Victorian times.

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