UNF better than metric?

old-git

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I have discussing with my chassis builder this afternoon about modifying my rear bottom wishbones, fitting rose joints so the toe in/out can be adjusted. The top wishbones were made to be adjustable during their manufacture.

He said that I should use imperial UNF threaded joints rather than metric as they are stronger size for size. This is due to the depth of the thread being less on a UNF bolt than the metric equivalent. Apparently, F1 teams still use imperial rather than metric where strength is an issue for this very reason. I guess it also means that smaller diameter bolts can be used resulting in less weight.

Can anyone confirm this?
 

T9 man

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I would be interested in hearing the answer to this one also! Still trying to get too grips with an F1 team (Technology Junkies) resorting to some Imperial materials :amazed:

There's still hope for the old ways after all ;)
 
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old-git

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I would be interested in hearing the answer to this one also! Still trying to get too grips with an F1 team (Technology Junkies) resorting to some Imperial materials :amazed:

There's still hope for the old ways after all ;)
They will use what is best for the job, regardless of how old it is.
 

old-git

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lol.

Ok, why doesn't someone make deeper threaded metrics?
Deeper threaded metrics would be even weaker!! The deeper the thread the weaker the bolt.

Thread sizes and design are now so deeply standardised that they won't be changed. For almost all purposes, metric thread design is fine. For specialist work where stength and weight are the important factors, there is already a perfectly good thread, UNF :)
 

SLEEPER

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F1 cars treat weight as king in every department.
I had never thought about metric v UNF but now I have it makes pefect sense
 

Charliep

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Your chassis builder is talking utter rubbish.

The general rule is that a bolt will have reached its full tensional strength at the depth being equal to its diameter. Additional depth can be given for a variety of reasons, which range from assembly to maintenance. Whatever thread type is being used is immaterial.

To increase the strength a material with a greater tensile strength should be selected.

The added length has one added advantage. When adjustment is needed on a fairly regular basis or the the bolt/stud has to be taken out then damaging the top of the thread will weaken it (even if it is not being cross threaded wear will make connections weaker). Therefore added length comes in handy.

Such constructions obviously add some more weight to it, which is in racing situation not desirable. But then living components is not an issue in racing.
 

old-git

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Your chassis builder is talking utter rubbish.

The general rule is that a bolt will have reached its full tensional strength at the depth being equal to its diameter. Additional depth can be given for a variety of reasons, which range from assembly to maintenance. Whatever thread type is being used is immaterial.

To increase the strength a material with a greater tensile strength should be selected.

The added length has one added advantage. When adjustment is needed on a fairly regular basis or the the bolt/stud has to be taken out then damaging the top of the thread will weaken it (even if it is not being cross threaded wear will make connections weaker). Therefore added length comes in handy.

Such constructions obviously add some more weight to it, which is in racing situation not desirable. But then living components is not an issue in racing.

I think you missunderstand what I am talking about :) I am not talking about depth or bolt length but about the diameter of the bolt between the bottom of the treads, the minor diameter of the bolt. For any given bolt diameter the minor diameter of a UNF bolt will be bigger than the equivalent metric bolt and, therefore, stronger.

However, as any sheer forces should be concentrated on the unthreaded part of the bolt, I doubt that the improvement in strength is very much.
 

old-git

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Ah, I get it. To have shallow threaded bolts you'd need shallower threaded holes in all your engines.
No. The major daimeter of the bolt thread is the same, it's the thread's minor diameter that is bigger on a UNF bolt compared to the metric equivalent. So the hole will be slightly bigger :)
 

Charliep

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No. The major daimeter of the bolt thread is the same, it's the thread's minor diameter that is bigger on a UNF bolt compared to the metric equivalent. So the hole will be slightly bigger :)
It depends on the pitch. The finer the pitch, the bigger the threads diameter.

bolts are designed for different uses, which are tensional, torsional or sheer forces or a combination of them.

The metric system has many applications that are not available in just any hardware shop.

The metric standard threads are designed to have a balance between pulling out the thread and the bolt snapping. In theory it should happen at the same time.

The applications work around the structural requirements. Whenever the strength can't be achieved within the accepted tolerances a different material will be sourced. Hence the all aluminium construction of the Audi A2 consited of 37 different aluminium alloys. For the same reason as well as others some bolts are standard pitch and others are fine pitch.
 

old-git

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Agree. But UNF is generally finer than the equivalent sized metric thread.

I have asked anther guy who restores F1 cars and he confirmed that they are built mainly from Imperial bolts. I have asked him why and will report on the answer.
 

Charliep

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Agree. But UNF is generally finer than the equivalent sized metric thread.

I have asked anther guy who restores F1 cars and he confirmed that they are built mainly from Imperial bolts. I have asked him why and will report on the answer.
When the thread is finer than the metric fine threads then you need a longer bolt as the thread can't take as much tension as the bolt (thread length needs to be longer than bolt width). The question is what you want to let go sooner if things are stressed over the limits or for safety reasons (i. e. accident).

Most of the F1 teams have been based in Britain, where the UNF was the norm. Designs have therefore been UNF based and therefore are still being used.
 

SLEEPER

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If there was even the smallest benefit of using any other thread over UNF you can be sure F1 would have changed.
 

Charliep

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If there was even the smallest benefit of using any other thread over UNF you can be sure F1 would have changed.
The thing is, there isn't an advantage to use one or the other in general. Both can be made working evenly well, depending on application and approach.

I am living engineering and not bothered with either of the 2c norms. What it boils down to is the material the threads are made of.

About 25 years ago I had to make some special bolts for some equipment that is stressed for more (and used on a daily basis) at 30.000rpm. The original bolts were failing to often leading to some serious problems. I spent 2 whole days in a steel mill going through data sheets to find the right steel.

25 years on we have many more available. The base material is where you start from.

Talking about racing. F1 is extreme in on way. However, other sports and other applications are extremely demanding too. The stresses on LMPs are extreme and metric threads are being used. Having worked a lot with Brembo brakes I can tell that they are happily using metric. In truck racing they use metric as well, braking 6 tons of mass. The list goes on.

It doesn't matter whether you use UNF or metric. I certainly would not convert a UNF designed part to metric or vice versa.
 

SLEEPER

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Yawn....................................
You really should spend more time reading what people have said rather than telling us how knowledgeable you are.

I didnt even comment on if there was a differnce I simply said that regardless of why UNF was used originally they wouldnt use it now if there was something better
 

Charliep

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Yawn....................................
You really should spend more time reading what people have said rather than telling us how knowledgeable you are.

I didnt even comment on if there was a differnce I simply said that regardless of why UNF was used originally they wouldnt use it now if there was something better
If you had thought about what I wrote you wouldn't have made such an immature comment.

Threading goes back many hundreds of years. Standards only came in due to industrialisation. Different global powers standardised them differently.

Rather than implying what my motives are, switch on the brain and use physics. You are speculating without understanding the full back ground. This is one great help for the thread. I am talking fact. If you would I would not have to do it.

So, refrain from silly and insulting remarks and contribute to the topic, but with factual input not speculation.
 

claymore

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If you had thought about what I wrote you wouldn't have made such an immature comment.

Threading goes back many hundreds of years. Standards only came in due to industrialisation. Different global powers standardised them differently.

Rather than implying what my motives are, switch on the brain and use physics. You are speculating without understanding the full back ground. This is one great help for the thread. I am talking fact. If you would I would not have to do it.

So, refrain from silly and insulting remarks and contribute to the topic, but with factual input not speculation.
Still waiting to hear what you do for a living and who you work for, so that we can all bow down before you and your superiour knowledge.
 

SLEEPER

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I see you still have not read my post despite your reply

The thing is I wasnt and still dont disagree with you (on the point there may be no difference in which is best)

So why you have to tell me how much experience you have (again) is beyond me.
Id also be interested where I imply anything to do with your motives -

We dont bring up your "abundance of knowledge" you do .......................all the time.
 

Charliep

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I see you still have not read my post despite your reply

The thing is I wasnt and still dont disagree with you (on the point there may be no difference in which is best)

So why you have to tell me how much experience you have (again) is beyond me.
Id also be interested where I imply anything to do with your motives -

We dont bring up your "abundance of knowledge" you do .......................all the time.
It might have occured to you that forums are information bases. What is the point of having the knowledge when it is not being used? Unlike the ones who want to make believe that only the 'chosen' ones can do the work I am, I give my knowledge away.

And to clarify this: If I make claims, I am being flamed. Yes, it has happened even here on the forum. When I bring proof I am going to be flamed because I am bragging.

Where you imply my motives? In the the last sentence of the quote and in the first sentence of the previous quote.

@ Claymore - Only idiots would bow down to me. Intelligent people go and make use of my knowledge. This is what knowledge is for.

And why do you want to know who I am? This doesn't make a difference of what I am claiming is true or not. I am going with the test results I am colating. These tests don't lie and they aren't hear-say. They are hard facts and this is what this forum should be about.
 

HDi fun

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I agree with CP that material selection is likely to be the single biggest factor. I am not a metallurgist, however.

This is why, for example, long bolts such as cylinder head bolts are designed to stretch during installation and for the same reason they cannot be re-used. A hard but brittle material would be totally unsuitable in this application.

One the other hand, a bolt that's simply used to clamp a jubliee clip is not really subjected to any forces at all other than extremely slight tension (stretching). In this case choice of material and thread pitch and depth are largely unimportant. Corrosion resistance would be the secondary goal. Cheap manufacture being the primary one.

@CP, I don't think anyone's trying to attack you. Torque Cars is not like that in general. I agree many other forums are so I understand you appearing slightly defensive when you really have no need to be so. All that's happening is people are clamouring to understand what it is you're saying. They're not looking for justification in order to flame you or discredit you when you provide it. There's a thirst for knowledge here -something I see as credible given the general low level of intelligence we see during our daily lives.

Welcome. It's good to have you on board.

Best regards,

Paul Anderson.
 

old-git

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When the thread is finer than the metric fine threads then you need a longer bolt as the thread can't take as much tension as the bolt (thread length needs to be longer than bolt width). The question is what you want to let go sooner if things are stressed over the limits or for safety reasons (i. e. accident).

Most of the F1 teams have been based in Britain, where the UNF was the norm. Designs have therefore been UNF based and therefore are still being used.
Why would you need a longer bolt? Imperial nuts are no longer than metric ones?

We need, then, to confirm whether Ferrari use metric or imperial.

I must point out that I am not claiming that F1 uses UNF only that I was told this recently. I have now been told by another guy who used to spanner for Williams and now restores F1 cars that they mainly use UNF. He reckons it's because the finer thread allows for finer adjustment.

My old boss's son is an aerodynamicist with Red Bull. If I can find his number I will ask him to ask his son.
 

Charliep

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When you tighten a bolt you obviously put tension on the thread. The finer the thread the weaker it will be and the bigger the the base diameter of the bolt.

The only way to counteract this is the have more thread length.

I have not claimed that F1 doesn't use UNF threads. All I am saying is that the strength of the bolt of a UNF is stronger than its thread on a UNF nut. Therefore you will need more thread for the same overall strength when it comes to tensile strength.

Obviously the UNF bolt would be able to take a bit more sheer force because of the slightly thicker base diameter.

With the finer UNF pitch adjustment is easier/quicker.

It boils down to preference. The key element is the bolt material, which will give you the strength needed.
 
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