Stuff you probably don't know about bolts (for car DIY-ers) | Auto Expert John Cadogan 

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As much as I enjoy your opinion pieces, these technical videos are by far your best IMHO. Extremely helpful. Thanks!

First form metalwork 65 years ago we were taught how to use a crescent (shifter) wrench correctly. The moveable jaw should be place so it is in compression while fixed jaw can located so that jaw is being forced apart. The correct orientation means the jaws fit snugly on the nut, and increasing force on the handle increases the clamping effect of the jaws onto the nut. In effect, increased force increases the locking compression of the jaws. Conversely, with the incorrect orientation, increasing force on the handle forces the jaws apart, with the eventual expansion causing the jaws to open so it slips off the nut, rounding the square ends. Hence the nickname. A crescent wrench will never be as effective as a ring spanner, or a socket, with care and skill, it is a valuable addition to the tool box. Similar principles apply to using many other wrenches, like the monkey wrench, the Stilson pipe wrench, and adjustable pliers. Some sneer at bush mechanics, until their problem is solved by the intelligent use of these primitive tools.

In a former life I was a test engineer for BP. Testing engine oil and fuel. My memorable lesson was about the co efficient of friction of materials. Stainless bolt going into stainless bolt or flange and what tolerance we need so they have a chance to be removed later. Steering lock bolts are fine examples of torque to yeild. They have a bolt head that snaps off them when it's tight enough and prevents a spanner monkey faffing with it. Cylinder head bolts stretch beyond the elastic limit by design. (Ford CVH engine) So a head gasket job means you need a head bolt set too because your original ones will not screw into the block.

As a dentist, I use a small deflecting beam torque wrench when screwing in implant crowns. The torque used varies from 10-35ncm, and these little suckers cost about $400 each. I know, there'll be those who say dentists charge a lot, so we can afford it, but I only use this wrench once every week or two-not 100 times a day like a tyre fitter might. Also, when I was in high school, (1973), one of my metalwork projects was making a copy of a Warren and Brown deflecting beam torque wrench. Still got it, but it's hard to calibrate.

Thanks for the Knipex pliers tip. When I first started messing about with bangers I came across a recommendation for "parallel jaw locking pliers" but couldnt find any, 50 years on you may just have finally hooked me up

Who’d a thunk the world of bolts would be so interesting. Time spent learning stuff like that is always worth it. More deep dives would be welcomed, and might stop me buggering something up in the shed. 👍👍

A really interesting and informative piece here, John. Well done! Loved it. Can we have more of this kind of stuff?

John, I believe that torque wrenches were first introduced in the 1920s. I was told by the bloke that taught me my trade ( a RAF engine fitter ) that Napier were experiencing random engine failures, when the chief engineer dug down into the problem he found that it was a big end bolt failure that was the root cause and that there was no consistent tightening procedure. It was was down to the size of the engine erector and how long a spanner he had in his tool box. If he was a gorilla with two foot long spanners the bolts would be over tightened and if he was a seven stone weakling (like me) they weren’t tight enough. Some of the engines I worked on had the big end bolts tightened to a specific stretch rather than a specific torque, which I think gives the same result.

Great subject covered with your usual informative and sardonic style. Good point about those overhead nuts and bolts. Lock tab washers help prevent them coming undone. You didnt cover the difference between tightening the nut versus tightening the bolt.

Knipex Pliers-Wrench - awesome addition to ones tool-kit. Oh - shit yeah, bolts matter. hey John - so many don't understand gaskets either. I'vehad me' WB torque wrench over 45 years - awesome tools.

Awesome video mate. I always learn a shit ton when I watch your channel.

A most excellent video. This is extremely valuable to the community in Australia and around the world. One of your best examples of qualified expertise. Thankyou...

I was skeptical when I noticed 46:11 for duration but I watched every minute - time well spent, Thank you,

Hi John, I am a draftsman working in the mining & heavy industry sector. We mainly use structural assemblies. They consist of a bolt nut & plain washer, class 8.8, with large heads. The washer has 3 small lugs to visually assist when using the part turn method. I have a chart that I use as the length of the bolt affects the amount of part-turn required.

Another ripper topic. Having spent some time studying torque of impact tools, factors such as extensions, wobble bits and lube make a massive difference. As you stated there is a big difference between torque on the bolt and clamping pressure on the part.

John, if you decide to do another vid on fasteners, I would love to hear your take on dealing with steel fasteners into aluminium, particularly when there is significant vibration involved. I would love to know if there are any tips for preventing vibrating out, undoing, etc, when you have to use low torque for fear of stripping the captive thread in the Al.

Thanks for this, i appreciate you sharing your in depth understand of metals and how they actually work, i could go down this rabbit warren all day. A couple of years ago i had a fast lesson on fastener quality when i discovered two missing bolts holding my front wheel attached to my motorcar. Previous owner had "upgraded" the rims that didn't perfectly fit so had to attach a 4-5 expansion plate, supplied bolts didn't work so they sourced some interior bolts from "you know where" , so upon discovering this i quickly learned what shearing meant. Considering the driving i had been doing just days previously at unrecommended speeds i consider myself very fortunate, so when my trusted mechanic gave me the invoice for replacement with original fasteners there was no batting of eyelids.

Yeah, loved the tech talk on bolts. Learnt some too.

Mate, excellent segment. I learned a lot. Thanks.

I found it very interesting thanks. I feel that now I have been educated my old rule of thumb, snap it and back half a turn, is no longer suitable. NASA has announced that spring washers do nothing but luckily for me I have been applying Loctite 262, which does come apart with normal tools, when working on my 4x4. I figured that I that I would prefer to have more difficulty removing a part than having it fall off.

Such a pleasure to listen to a someone who know what the hell he is talking about. Thank you!

I had a old 1st generation pajero with a V6, we were replacing the head gaskets and lost one of the washers that came in the head stud kit... so we went to bunnings and got the closest washer we could find hahah. The engine did about 30,000km, before the mate I sold it to decided to replace the engine since he was present for the "rebuild" but it was running fine for a 400,000km bodged engine.

Takes me back to my early days as an engineering student and new graduate mechanical engineer working in heavy industry. In my even younger days used to play rugby at Mudbank (Meadow bank) always muddy and best of fun and the Parramatta River was a tip

You needed to replace my College professor on the Material Resistance Course back then, you made nuts and bolts quite literally entertaining for the entire 45 minutes of the lecture. I didn't doze off, astounding work! My entire Mechanics Degree needed more teachers like yourself, that really know their nuts and bolts, pun absolutely intended. Just a handful of them actually practiced their craft; those were the good ones.

I had watched this a while back and was working on some engine mount bolts on my motorbike. Other owners had had issues with stripping threads due to seized bolts so I though I though I would check mine and use antisieze. The 12.9 bolts broke free but it took some effort so i set to lube them with some general grease and put them back in while I sourced some copper grease. I stupidly torqued them to dry spec thinking there was tolerance in the bolt but there wasn't. They had stretched and wouldn't go back in so I had to order new bolts. I had to hunt this video down because it's the only one where i've heard someone state how much to reduce the torque for dry vs lubed.

I love my W&B torque wrenches! I use their deflecting beam types in the electrical generation industry. With care, these things remain spot on with calibration for a long, long time. Never loan them out to anyone so you know the history of use.

Hi From the uk I quite liked the assembling of con rods to crankshaft on the old triumph twins using a micrometer to directly measure the stretch of the fastener also used this method on a medium speed marine engine big end Keep up the good work

Very informative nice one John much appreciated

Excellent video John. My Grandpa was a tool maker as well as a fitter and Turner. So some of what you've been saying makes a little sense. Go easy on the Skoda phobia. They're pretty good and far better built than their VW/Audi relatives. We have an 11 year old Fabia that's only had new tyres, battery and full services and no issues. I'm not alone either. My key to Skoda success was keeping it away from the dealer.

@ProjectFarm has recently done a video on his channel called “Best thread repair”. There were some that exceeded the thread strength of the control alloy used in the experiment, highlighting a decent thread repair is not only acceptable but in some circumstances could be better than pre stripped thread.

i am a HD tyre fitter, we investigate when wheels come lose in the mining industry and we find a lot of the time people just do not tighten the bolt to the required spec as you stated or, mating surfaces are dirty and rusty. the sequence is also extremely important, i remember the Holden v8 super cars years ago had rims cracking in half. this was due to insufficient torque setting. it was really interesting.

33:15 John is correct for 99% of fasteners, however I’m seeing more and more ‘stretch’ bolts with a reduced area in the shank that I believe is when the actual stretch occurs. The threads are perfect, however if you compare a new bolt with a used bolt, you will see an elongation in the used bolt.

Thank you John. A very informative session.

I have run 2 Fabias for over 200,000 k’s each. Tyres were the big expense , but I wrecked the block in the blue one and the body in the red one

I work as a washer squasher (mechanic) and it’s nearly comical if it wasn’t so dangerous what some people try to secure on their cars with the finest chinesuim grade bolts.

Some years ago I had an information booklet from Cleveland fasteners, in it they stated that as long as the internal stresses of a bolted item were greater than the external or applied stress the joint would never fail. Way back I had a diesel engine with a centrifugal oil filter and cast into the top was the message "finger tight plus three quarter turn, alway stuck me as funny as this would depend on the size of the gorilla doing the finger tightening or me as I was then a weedy 15 year old.

When I worked for M Benz we tensioned the head bolts to 28 Nm then +90 then another +90. This was when many other cyl heads were still using full torque settings. Stretch bolts are the go!!!

“grinder and paint makes me the welder I ain’t”

Hi John. Why do plate washers fit the bolts so loosely? Is this intentional? I get real OCD about this sometimes and will often use the next size smaller which requires filing/drilling for a good fit. The more visible the application, the more likely I am to do this as it makes my fabrications look wonky with sloppy washer fit. Is this a bad idea? Are poster-sized prints of you wearing fishnets available?

I've still got my old W&B deflecting beam tw. I have a 25 Yr old Norbar that I use for general purpose and a slightly newer Norbar purely for wheel nuts. Then my latest one is a fancy Sidchrome digital that does torque angle.

John an old joke I remember from school. Fastener manufacturer John Nutts bangs his cleaner gets her pregnant and does a runner. Headline in local paper: Nuts, screws washer and bolts 😉 what a great informative piece again. You really explain in easily understood phrases this seemingly dark art and I know from experience that my Jedi tightening is shite when I changed a wheel on my son’s first car a Renault Cleo and the thing came loose, fortunately found our before a major incident 😱

Great tutorial thanks John.

Thanks, John. Great information in this video. ?: Have you ever used Boeshield T-9 rust and corrosion protection? Originally developed by Boeing for the aerospace industry.

Awesome video! I knew when I saw DIY in the title I was gonna get schooled hard as a home mechanic :)

This is the best video I’ve ever seen you do, still has your style but I’ve learned that some situations I’ve used high tensile bolts to replace older bolts it’s not the best idea

Proper education…. Keep up the good work JC

I've seen a cuople of interesting bolt related things on YT lately, from Allen Millyard checking the calibration of his torque wrench with a spring balance, to Edddd China stripping the "threads" formed in an alloy suspension arm with a trilobe bolt. That was repaired with a timesert, making it stronger than BMW did. If I need a replacement fastener, I go to a fastener specialist. I get exactly the right thing.

I used a torque wrench to reinstall the bolts on my strut tower brace just the other day. Would you suggest also replacing the bolts? Not sure if they are intended to be one time use only. Carmakers are generally poor at communicating those details.

Heavy going for the average bodge it and scarper 😉 but also very informative 👍 Much appreciated, thankyou

Great stuff John. I really enjoy these ones, have ordered my 123 blocks due to your other video ;-)

@TorqueTestChannel did a semi recent video called “Strongest Head Stud” where they test the strength of various LS Head studs. A good practical display of some of the discussion in this video.

Thanks John. This was rivetting! Or may be not? I learnt so much. Thanks. You talk about lubrication of fasteners. Ii have been told by many, many people to use copper paste or similar on practically every application - wheels, cylinder heads, suspension parts, door hinges etc. Is that the case and if so, does the amount used impact on the ability of the fastener to fasten appropriately?

Thanks John, great piece. I recently had to replace the bolts on the lower ball joint, which is also part of the steering arm on an old charger. Is a grade 8 bolt sufficient for this application? Many thanks.

I noticed when working on a gazelle helicopter, the engineer checked the torque wrench against a very accurate dial gauge on the hangar wall before using the wrench, very impressive!!

Good Video John - As a Suggested future topic - I wonder if its worth going into the differences between rolled threads and cut threads on bolts and studs........ most people don't know about rolled threads.... and they probably should.... DUUUUUUUUDE

Thank You “Doctor of Physics” I for one , really appreciate you.

One of my older workmates (he's 70, I'm 60) had to tighten some critical bolts to 20Nm. He used the old scale on the wrench, and went to 20ft.lb. = 27Nm. Buggered the shims.

Bloody good information. Thanks John.

I'm from England too, just like too add I always use a torque wrench and never reuse a torque to yield bolt. But do admit printing off a 360° printable sheet, laminating it the sticking it to a lid of a chocolate tub 😅 Didn't know not to use a torque wrench from a percentage either side of its range, but makes sense.

Always funny, to get a UNC bolt and a Metric nut to 'join' by the use of enough 'Oomph' to get it going... Oh, the 'Nut' makes it a 'Bolt,' otherwise it's just a 'Screw'... And just for fun tighten a 316 Stainless Steel nut and bolt together and then have fun stripping the nut taking it off again (you need dissimilar grades of Stainless so they will 'slip' to be able to undo them again, 2 of the same grade bind/fuse together....lotsa fun!) Oh, by the way, the skunk works was 'established' in 1943. Rolls Royce had a shaved bolt that a BSW nut of a special type would only tighten to a particular point and could not be tightened any further, the nuts and bolts were 'paired'.

I had a lot of stress back in the day bolting on foot pegs to my moto cross racer. Too strong leaning over dragging them in the dirt at 155kph they would tear the down tubes out of the frame Just saying leaving a foot peg behind at the first corner made for a difficult race

A particular employer of mine challenged me to the "Jedi" test. He was an engineer. On a couple of jobs that I did every day, with the same tool, I was less than 10% out of spec, on extreme spreads. More often than not, I was close to spot on, within a few percent. When challenged with "Guesstimating" applied torque on jobs that I didn't perform regularly, and with tools that I didn't use regularly, it was a little bit embarrassing, to say the least. If you can get within 35%, good on you, you're doing better than me.

Take it from me, 3 semi loads of bolts chucked into a lay down yard. Then organising them according to the pn id is great fun

Don't expect your local dealer's workshop to operate like NASA. I have seen enough people struggling to get wheel nuts off on the way to DPC and I once had to use a 2 meter extension and plenty of muscle to get a diff drain plug off. The rattle gun is quick and brutal.

John, when are we getting bin cam so we can see where the shifter goes?

Hi John, when you mentioned backing off the torque number by about 30% when using lube, it kind of does my head in. I am assuming, that because of the lubrication the nut has less friction when tightening? Thanks

Thanks John, very enjoyable and informative video. As a mechanic it really shits me when I see an ad for a car service or similar with the "mechanic" holding a shifter [nut fucker] . Have a think about bringing the pen back please as it would have been a useful tool when pointing to sections of the bolt. On the subject of bolts it would be really really good to describe the various types. Keep up the great work, Mal

I recently used a M12 (10.9) strength for my car’s belt tensioner. Finished in black oxide. The factory bolt was maybe zinc coated. I ordered the factory bolt despite the $21 USD price but had to arrive from Europe. Certainly I didn’t want to wait 3 weeks. The black oxide bolt is working…the threaded female part the bolt goes into is not steel but some sort of aluminum or magnesium cast alloy. Should I worry about a corrosion issue between the metals?

Why do we have 3/4", 1/2, 3/8"" and 1/4" wrenches? What size is ideal for torquing wheel nut on a 4WD and sedan? Is 1/2"wrench good enough?

I love my torque wrenches. I have a small 1/4 drive and a larger 1/2 inch drive. Many moons ago I owned a Kombi with a 1600cc motor. The crank bolt had to be tightened to 400ft/lb. Luckily, the local hire place had big lump of a torque wrench for when I needed it.

This was great ❗Thanks

Use torque wrenches on your oil bung plugs and transmission plugs at least the 1st time. Stripping or cracking the castings down there could be a death sentence to w/e box is associated. That said I hand tighten my steering fasteners no torque wrench just offset double-ended ring spanners. But I do use loctite on the ball joints. Other things I use the torque wrench on are spark plugs and recently I used it to torque my swivel pin bolts which were replaced with brand new grade 8 hardware. I drive a Jimny, you could probably do a whole episode on that rig hahah.

I can not disagree with anything you said, but I look back at my 50 years of bush mechanics and wonder how I survived 4 million kilometres of driving ( mainly taxis) doing a lot of my own repairs. many dozens ( hundreds?) of wheel changes over the years, all done by feel. More than dozens of brake changes, belt changes and quite a few gearbox exchanges. In the old days we would buy alternators and starters from wreckers and fit them at the side of the road. In the past never owned a torque wrench. Must have been lucky. Love the videos, hope I win the Bluetti.

Nice work, thank you. Riddle me this though ... why when I'm using a stubby screwdriver do I struggle to undo the screw but if I swap to a 250 long screwdriver I can easily undo the screw. Where does the extra torque come from?

when the video started I was thinking head gaskets were a great example that needs specific torque to do its job best and with it needing to seal water, oil, and combustion pressure; accuracy helps a lot with current day precision and engineering compared to a 30s V8 with a soft gasket; which a lot of the rumors of 'just tighten it up' must come from though I don't think many are alive that worked on them with any regularity.

Dear John. I heard you mention a bin cam while listening to a podcast a couple of days ago. Just a suggestion. Maybe do a bin cam and add a montage at the end of your vid so it's not disruptive while your loyal viewers/listeners are hanging off every word you say. Could be entertaining though it will mean more work.

Where does hydraulic tensioning fit in the great scheme of things? Totally impractical or the Jedi and the average shed guy just wondering.

Always love Aussie made tools, gonna check out those torque wrenches :-)

Square plates without a radius. Either bolted or welded. Does my head in. Same principal as the radius shoulder.

Just recently purchased an Angular (spelling) gauge, why it was a good price on a good brand and it may come in handy one day.

Real info thanks brother.

John, could you please explain for those that don’t know, how extension bars affect torque settings

BRILLIANT !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! Thank you ... ... ... You really have a very special way of using your fingers on nuts :)

There was a lot of torque in there, like you were trying to stretch it out. You weren't just screwing around with us? Or was it all some pitch. Sounded a bit nuts, seemed to go round n round. I felt like yielding, but I was quite galvanised by it all. I think you did socket to 'em

As an actual toolmaker, I approve. Also, 1.25 microns can be quite large.

I am wondering how much torque wrench calibration is a factor and if so how often to check for this

Teflon coated bolt and gasoline (brake cleaner) grease tighten by clicking torque wrench is kinda spot on and really easy to apply on field. Bolt is rust free and consistent friction, brake cleaner is cheap and clicky wrench is kinda good way to have consistent speed. Digital torque wrench is the worst. They have lag and you gotta go slow. Downside is bolt and nut are garbage after one use. That is kinda standard for steel cable assembly in my area. In some application for cable is better to let go at certain point. You can use steel sleeves and press the shit out of it but. For radio tower is better to have 1 meter slack and and cable which is gonna slip at some point.

You made a brief reference to "ugga dugga" jobs. I was disappointed you didn't delve more deeply into the science of ugga duggas and how many should be used in different fine tolerance engineering situations.

What about telling us something about lock washers, and lock nuts

Very good information thank you 👌🖤💪

All my 10mm sockets seem to turn into 3/16 Whitworth, until I buy a replacement.

What I love about this kind of video is how it 'threads' lots of things I know into one piece of knowledge. I'm not saying I knew everything but there were lots of things I did know in isolation that I now know where they fit together. That time no pun intended. The one about checking by threading down the nut I learned from an old guy years ago but he didn't really explain the theory behind it. Thanks John.

Factual and brilliant

You do love this Sh!t, don't you? Well done, very well explained, and thank you 👍

I've been a Licensed Aircraft Maintenance Engineer (mechanic) for the better part of three decades and I have never owned a shifter. I couldn't agree more. The only thing I have seen worse than a shifter is a set of Knipex nut fuckers. AKA Knipex parallel pliers. Keep up the good work JC!

Tomorrow's lesson, coarse vs fine thread clamping force and torque settings. 😁😆

I remember the “ Wrist Click “ method to replace better shit.😊

Thanks John. Now my RU-vid feed is all about bolts and screws

Then you get the really tricky question of how tight do you do up a bolt-nut combo when there is a nyloc or self locking nut in the equation?