Screw It! Intro to Fasteners & Bolted Connections

Mechanical fasteners like screws, nuts, and bolts are fundamental components in any machine or vehicle. In this video, we will walk you through the basics of:
- Different fastener types and shapes
- Drive types
- Materials and coatings
- Galvanic corrosion
- Coarse vs fine thread
- Best practices of joint design
- Helicoils and heat-set inserts
- Calculating the correct preload and torque
- Vibration control methods
And we'll answer that age-old question: what's the difference between a screw and a bolt?
Companion blog post (with additional reference materials): tarkka.co/2019/07/07/screw-it...
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Tarkka Shop: www.etsy.com/shop/tarkkadesign/
Connect with us!
Website: www.tarkka.co/
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Twitter: / tarkka_design
LinkedIn: / tarkka-design
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Some video footage is incorporated under a Creative Commons license and is credited to:
bry so (Incredible footage of ironworkers in Georgia)
• Ironworkers building G...
NT Department of Trade, Business and Innovation
• Northern Territory Ind...
Other video footage is furnished royalty-free by the following organizations:
National Aeronautics and Space Administration (NASA)
US Department of Defense (DoD)
North Atlantic Treaty Organization (NATO)
Ford Motor Company
Fiat Chrysler Automobiles

[@halogod0298]

I love they way you flamed up the split lock washers 😂

[@danielplaya4211]

Frl, the disrespect 😔

[@sky173]

With more videos like this, this channel could easily be one of my favorites. I hope to see more!

[@tarkka]

Thank you! More to come soon :)

[@whollenbeck8]

I second that! :)

[@justin60222]

Never knew the unthreaded areas were for shear. Awesome!

[@MrCharliebbarkin]

A rare gem on youtube, a very informative video with no fluff, no time wasted. Great job.

[@jabzerloo2699]

Thank you I've been trying to convince everyone at my work that split lock washers don't anything special.

[@Hackwurschtable]

In my technicians school I was told that the norm for that even got withdrawn.

[@stalwardstallion]

You were right..Split washer is not used ay were in where the critical fastening is required,

[@yangxinkai]

Split lock washers do help in mild vibration conditions. They are applicable if the connection is tested in service and proven to be sufficient. Otherwise wedgelock is a much better choice but the cost is much higher. We have applications with no lock washer, with split lock, and with wedgelock.

[@hanhdhsj]

@@Hackwurschtable Habe letztens die Norm dieser Dinger gesucht. Wikipedia meinte dann "Nachdem seine Wirkungslosigkeit erkannt war[2], wurde die entsprechende Norm zurückgezogen." Hat mich gut zum lachen gebracht :D

[@cablenowadays6586]

@@yangxinkai They work very well in low torque applications on vehicles. Like lighting adjustments or bolt on accessories. I use them all the time actually.

[@MaximilianonMars]

The music gives me "How it's Made" vibes, very nostalgic! I love your work. Excellent video, it's information dense and I'm learning a lot every video.

[@FireStorm4056]

I hope you start making videos again soon! Your videos are simply the best out there for a lot of these important engineering topics that often don't get much coverage in undergrad curricula. Your short-form, no-nonsense style makes these some of the most valuable and information-dense videos out there (perfect supplemental material when we teach machine design courses!) Hope you are well!

[@tarkka]

Thank you so much!! We are planning on making more soon!

[@evanparker]

i have been a mechanical engineer for 11 year and this video is 100% correct, except maybe for the major diss to lock spring washers. spring lock washers definitely have their place, although not in any sort of critical vibrating assembly. they are used a ton in big construction stuff, bridges, big casting forging bolted joint type stuff with much success. nordlocks are amazing but about a zillion dollars amazing for your airplane, but not for everything. Even as a believer in them, I will admit that there is a lot of correct information floating around that the spring lock washers are not as useful as many other methods. They have lots of weak points, but they're incredibly cheap. superb video!

[@hammurambi]

This channel has a lot of good information. This video and the one on making engineering drawings are particularly helpful. I really hope to see more from you guys soon.

[@searching616]

Please make more of these these are so detailed and interesting.

[@whollenbeck8]

I just watched your Engineering Drawings video and now this one. I have to say that this is so much in my wheelhouse. You folks do an excellent job with your videos that they have the same quality as the 'How It's Made' show on Discovery.

[@brianbender7438]

Excellent work. I have been a mechanic for over 50 years, working on many different types of equipment and still learned some new information tonight. Thanks a lot. Keep it up.

[@byte_dance]

This channel is gold!

[@RaymundoGabriel]

Thank you for such amazing videos. I hope you keep doing more, I'm learning so much from you.

[@4n2earth22]

Wow! Top shelf info! Excellent research and delivery. Thank you for all the hard work that went into this vid. Exceptional!

[@moshe778950101]

This video summaries this issue so well. I have watched numerous engineers talk about screws and means to prevent them from losing pre load. You did that in less than a minute. Would love to see more videos like that

[@reneseib6532]

this content is amazing and i love how you both take turns with the voice over, makes it easier to learn from some reason

[@we-are-electric1445]

As an electrical engineer I found this video fascinating !

[@nayzawaung9]

The purpose of this video is so beneficial for everyone who is interested in engineering, I'd like to suggest that it would be great if talking is a little bit slower. Some viewers are from non-English backgrounds like me. Otherwise next time they will skip your videos if they don't understand them. Apart from that issue, everything is great to watch and learn and even gave me lots of ideas through the video.

[@devops9506]

I worked in CNC machining for almost a year and I found out more about fasteners from this video. Thanks! Please keep up the good work!

[@key2010]

a year isn't a lot to find out ... i made mistakes my entire first year out of college, from unrealistic tolerances to out of standard threads to wrong scale drawings and wrong sheet sizes :D... boy, i sure gave my boss heartburn ... nothing like slaving away underpaid to make your boss tolerant to rookie mistakes

[@coreyrosteutcher8429]

Very good channel. I appreciate the research and the obscure subjects that most overlook but as you said are the nuts and bolts of nuts and bolts so true. Please keep making videos

[@georgeboaru5935]

Thank you for the efforts put in making this video. Really useful!

[@AertPietersz]

Thank you so much for making this. I learned so much from it and it pointed me towards a lot of areas that I need to learn more about.

[@Sk8n2Enjoi]

This is the way informational videos should be produced! Great breadth of information, in depth information, explanation of the terms used, and spectacular visual aids. Keep up the great work 👍

[@johnsmitty4516]

Absolutely top notch content here. Good work!

[@Spectrum3847]

This is a fantastic video as are others on your channel. Hope you are able to produce more in the future.

[@EverettWilson]

Thanks for the video! If there's enough material, I'd love to see one on different forms of threads, and especially when different tolerances are used.

[@Rycamcam]

Super helpful video, and channel! Thank you for uploading these. Hope you guys do more

[@dansv1]

Great content. Bit of humor at 4:53.

[@truetilde4162]

dude this video was freaking amazing! taking a component design for mechanical engineering right now and this helped so much. great video

[@overfortea6937]

I was quite lost in my lessons, but seeing all these examples with real life videos accompanying them really put everything into place in my mind! Thank you so much! Great videos and of high quality!

[@bingosunnoon9341]

Another good video. I had to pass a written test on the Federal H28 thread manual before moving from apprentice to journeyman machinist classification at McDonnell Aircraft. I can still quote a lot of it fifty years later. Four years of training is something that doesn't happen anymore.

[@mikeyh6104]

Great video...Great Channel. This channel seems to have found a niche filling the gap between what I wish I had learned in engineering school and what I actually learned. For me much more useful information than knowing how to calculate a line normal to a sphere by hand.

[@ishimomo7842]

This is an amazing video. Thank you for all the facts~ I never knew I could learn so much about screws and bolts~.

[@LDam-pf6lx]

Thanks a bunch for this quick overview!

[@dellangdale4071]

Great video, thank you for posting!

[@ALXG]

@tarkka, I love you guys!

[@tjvanderloop1686]

Your "TARKKA" people has a great KZbin Video. Thanks for the excellent information. The Machinery's Handbook is certainly the finest resource for a beginning. (Fastenal is also an Excellent Fastener-reference.)Thank You! T J (Tom) Vanderloop, Author, Mechanical Designer, & Manufacturing Consultant. ATEA, AWS, & SME-Life/Leader

[@TabletopMachineShop]

Awesome video! There's so much material to cover, I think it would be awesome if you guys did a "part 2" or even a series. Keep up the good work!

[@tarkka]

We definitely didn't cover everything we wanted to. Still trying to figure out how much people can take in one sitting!

[@tarkka]

@@ravindrawaghela9072 We would love to do a video on that -- it's on the list :)

[@bobvines00]

@@tarkka Could you also go into the details on how to determine when to use different washers? I mean, when are "hardware store quality" washers OK vs. when are "spec quality" washers needed. I can make a good guess at some of this, but I'm sure that you have lots of ideas and good ideas that I've never thought of.

[@tarkka]

Bob Vines that’s a great suggestion!

[@alexliao6847]

‪We are a China factory of bolt ,nut ,screw and other fasteners with top quality and beautiful price.‬ ‪We have export fasteners to many countries all over the world.‬ ‪If you have inquiry recently,welcome to contact me ‬ ‪Email:[e-mail]‬ ‪WhatsApp:[phone]‬

[@BrianHoff04]

Terrific video covering a lot of information. Might I suggest reviewing the audio levels of the two different speakers. Some of the narration was very light & I had to turn it up a bit making the other narrator a bit loud.

[@finnigan16]

Please make more of these!

[@michaell8835]

Such an informative video, well done 👏🏻, really enjoyed watching this, and saved for future reference 😬👍🏻

[@wildone838]

Subscribed. This was a fantastic presentation. Fabricator of 12years.

[@jchidley]

Your videos are excellent.

[@26mridul]

extremely helpful! Can you make an intro for springs?

[@ryanho7033]

Such a helpful video. Subscribed.

[@danlebich]

hahaha this video saved my class presentation, this is the info I needed!

[@ttalvit1e]

In Finnish tarkka means exact, accurate, precise. Seems fitting.

[@roberthurley2412]

Excellent presentation

[@dmytroi5456]

4:53 nice packing for single screw)

[@officer_baitlyn]

its like letters dont exist

[@JaySmith91]

Excellent video

[@TheNormalUniverse]

Awesome video!

[@gryn1s]

quality content. also packaging of industrial goods at 4:56 is on point

[@MesquiteAutomotive]

Fasteners are a big part of my job. I enjoyed this. Thank you.

[@catalyzt7162]

whats your job?

[@litebohosekonyela67]

Hello. What’s your job lol?

[@MesquiteAutomotive]

Engineer in an automotive factory.

[@jaschawilcox1868]

Loved this! One piece of feedback: surprised there was no mention of thread forming fasteners in softer material applications (ie. plastic thread formers, non-ferrous thread formers, etc.) There is a lot that goes into plastic thread formers, especially in consumer products.

[@tarkka]

Thanks for your feedback!

[@pablo55343]

Really like your videos

[@rahuldumu8456]

Awesome.. please make more videos

[@Frank-bh3cm]

Information density is off the chart. thx

[@jimsvideos7201]

There are washers which are two metal elements with little dots of wax between them. When they reach the design compression load the wax (dyed a bright color) squeezes out.

[@wtacademy5091]

Beautiful.

[@lokgatorindustrialfastener7786]

Impressive👍

[@jjacowino]

Muy bueno!!!! 🙌🙌🙌

[@dawgyv72]

That wax stuff is pretty cool

[@erikisberg3886]

Enjoyed the video. Agree on the general uselessness of split ring lock washers, for small screws they seem to increase failure rates. When at college I built a lab for ME students that graphically measured clamping force vs nut and bolt torque for M8 screws. Some Zn plated and some stainless screws did reduce clamping force below 50% the second time torquing them down. If at all critical, thread length and correct lubrication seems as important as correct torque and angle. Subscribed to Your channel.

[@SenorGoodLife]

Really good video. Incredible info. I would add specifying that UNC threads are stronger for weaker female material like aluminum since failure more likely to occur along cross section of thread and UNF is better for stronger female material like steels where failure occurs along minor diameter of fastener.

[@LAG_Kuroneko]

This Video tells so much within 12 Mins

[@tuva600]

(EDIT: turns out I mixed up belleville spring washer and spring washers) The mechanical engineers I work alongside doing electronics uses (belleville) spring washer all the time. They ensure good electrical connectivity in the power-electronics designs. Connectors are often made out of soft metals that can deform over time (e.g. due to temperature, pressure, vibration etc). If and when this happens the (belleville) sping-washer "springs into action" and pushes the two mating surfaces together.

[@usamahibrahim2201]

subscribed!!!

[@framavia2201]

Interesting Video - Split washers and toothed (MS35333 type) washers are often specified in the aviation industry, almost always between a plain washer and the nut. The plain washer is free to slide against the part, so the only way they can have much effect is by maintaining a little pre load if the fastener begins to loosen? I suspect its true that they have little real benefit, but I must always install them as specified!

[@joechoi3699]

The hex head screws belong to the big family of screws. Which of the following descriptions related to the hex head screws are true: This type of screws is that it is not strong enough for most application scenarios Avoid confusing hex head screws with a hexagon socket head or an Allen, which have an internal hexagonal socket that is driven by hex bits or keys. Hex heads always have an external hexagon head. This type of screw requires a fair amount space to accommodate the tool. The price of the hex head screws usually very high

[@SquidIndustriesco]

Hey Tarkka, loved the video. Could you briefly go over why an increase in grip length results in higher resistance to loosening? Also, at 10:43, you mention the deformed thread lock nuts. Is this the same thing as the locking thread operation at 11:49?

[@TheEnglish2011]

Not sure if you only wanted a answer form tarkka but I have done some research on this. I think the long neck acts like a better spring. Allowing changes in load to occur with out thread deforming or changing shape. As for the lock nuts. They are the same technology. But I don’t like thread deforming because you can’t reuse the nut. Many nylon locking nuts can be reused.

[@SquidIndustriesco]

@@TheEnglish2011 That makes sense. Thanks Geoff!

[@gaffney92]

Spring washers, could you guide me to information as to why they are ineffective please? Again great video!! Invaluable!!

[@PhatToni]

I did sub during this vid - good content! I think Split washers and nordlocks perform the same task, although the former does a better job, neither increase breakaway torque but both resist vibration

[@tarkka]

Thanks! And there is another comment thread here that goes into why split washers are not good.

[@thealchemist5376]

Excellent video, thank you! I'm enjoying your channel.

[@jakewagner7416]

If I could make a suggestion on the video production side of things, utilizing a "de-esser" on your audio would go a long way in making everything sound a bit more polished and comfortable to listen to. Especially on a video where nearly all the information is in the form of audio. This channel is making great stuff either way.

[@mariajoseuseromatute515]

Nice and clear, but you forgot castle nuts with cotter pins. They are not as popular due to the additional costs of drilling and the pin, but they are wonderful in some circumstances.

[@andreasbeier2431]

Damn, I don’t get it. Why isn‘t youtube full of channels like these? Feels like university!

[@makarlock]

Great video! I have just discovered your content, and its amazingly concise and straightforward. You guys even machine examples! I have begun using your videos as part of an on boarding procedure for undergrads at my rocket club. Question about lock wire: from what I understand, it does not affect the preload or the vibe resistance of the fastener, it just prevent a loose screw from becoming dangerous debris in applications like turbines by keeping it connected to the other screws in the event of backing out. Is this true? I’ve been thinking about it, and i can see how the lock wire can prevent the fastener from backing out but it seems like it can’t add preload to it or prevent the fastener from breaking the static preload friction. Are there any good resources documenting the behavior of lock wire that you know of? Thanks!

[@lohikarhu734]

At 4:15 the grades of strength are shown, but the text for the metric ones has the same 4.6 class for all of them...

[@mikeyh6104]

Could you do a video on piping schedules and types?

[@yangxinkai]

Cyclic load does not affect preload setting. Sufficient preload is critical to minimize cyclic load effect on the joint. If the cyclic load is causing preloaded screw to reach critical stress limit, the solution is to increase the screw size and/or the number of screws, not to reduce preload. Reducing the preload will cause the cyclic load to increase its effect on the joint. Unless there is material strength constraint of the tapped hole material, preload of 75% proof load of the fastener should always be applied whenever possible, especially for cyclically loaded high vibration applications.

[@aviator-BY]

Would be great to see hi-lok and hi-lite fasteners in this video.

[@barisucarsoy]

This channel is VERY helpful. Thank you for all the effort. PS: you guys might want to consider narrating a bit louder.

[@tarkka]

Thanks! We appreciate the feedback!

[@bobvines00]

@@tarkka Yes, in some of your earlier videos I had to turn on KZbin's closed-captioning to understand Betsy's quiet voice. These last two videos were better, but a higher recorded volume would be great. I'm looking forward to your next video! Speaking of hard of hearing, perhaps you could touch on designing for less noise? I'm past where I should get hearing aids due to noise at work. And I'm a just-retired Mechanical Engineer, not a Machinist or other Artisan who has to stay in possibly noisy environments around loud equipment all day. :(

[@tarkka]

Bob Vines Acoustics and noise control is such an important topic that a lot of people overlook. We would love to do a video on acoustics and noise control.

[@ninemilliondollars]

This was very helpful. Now when I pull a bolt, or is it a screw? out of the jar we'd been saving for ever, I'll have some idea of whether it's useful or not. Thanks.

[@iceyliu7132]

nice

[@lolx400]

8:07 I believe the forces are transmitted by the high friction between the parts, that is caused by the bolts and not by shear forces?

[@flemish4]

If you fix the ssss sound this channel will be good

[@andrewclements6371]

Hello IRHS 2019-2020 Auto Class, its ya boy, my father left when I was only a youngling.

[@RinksRides]

should have named you Sue.

[@kylelaw7210]

A castle nut with cotter pin is another good way to keep a nut from coming off.

[@ToyotaKTM]

On your "Strength vs Corrosion Resistance" chartS, the "Relative Cost" box has the blue and green hexes reversed. The people who request that the video be slowed down, can use : Playback settings / Speed / 0.75

[@tarkka]

Thanks for spotting that! We will fix the graphic on our website.

[@nikhilbhale79]

You missed a pre tensioning method of elongating the bolt by hydraulic jacks and fitting the nuts. Nuts are hand tight initially and after hydraulic pressure is released the bolt contract and is pretensioned by correct value. Used on marine engines.

[@martinpconti]

Why do grower washers have no place in engineering applications? What's the source info for this affirmation or where can I read more about this.

[@michaelbettati6440]

What specific faults do spring washers exhibit? I just see them everywhere and was wondering.

[@ordinarypinoyreview1843]

I am using a 12mm bolt and nut for the installation of tow hitch receiver for my bike rack. Is it not a good idea to use 14mm washer on a 12mm bolt? What is that 2mm internal clearance going to cause? 14mm washer is what's currently available, so i used it. Should I remove and replace it with a 12mm instead?

[@Gigaguenther]

really good at 0,75x playback speed. makes them sound like actual people

[@paddykulkarni11]

You guys mentioned that the spring washers are useless. What is the reason for this? We are using them in a few of our valves.

[@Rushan.online]

I need some ideas about Mounting methods for thin-wall cast aluminum I'm Having a cast aluminum enclosure with a 3mm wall thickness. now I need to mount this to a mounting plate fixed in vertical walls. and my thread engagement is 3mm I need to increase the thread engagement. can I have some idea on how should I choose the appropriate fastener? 1.cast aluminum enclosure 2.mounting plate, for now, I have placed a 5M countersink

[@chiquinhoreydelas]

great video! just one question, why are those split washers useless?

[@tarkka]

Thanks!

[@tarkka]

As far as the split lockwashers go, there was some research done in 1969 by a guy named Junker: saemobilus.sae.org/content/690055 Unfortunately, that paper requires a subscription and I couldn't find it reproduced anywhere on the internet, but the results are summarized in this whitepaper: www.boltscience.com/pages/self-loosening-of-threaded-fasteners.pdf I have read that NASA repeated this testing and had the same results, but I can't find the report anywhere.

[@bucypher1]

Yes, in general split washers aren't resistenant against vibrations. The toothed washers can be used, they are cheaper than Nordlocks, but not that effective, so Loctite is a way to go in most cases. But, one must be careful, since different producers make the thread lockers make them in different colors.

[@tarkka]

Fantastic!! Thank you for finding this!

[@bucypher1]

@@tarkka You may also mention using flathead screws for location/positioning parts (ofc, it's tolerance isn't the tightest) and also using cone/flat set screws for holding other parts. Pretty sure You already know all that stuff ;)

[@rexmyers991]

EXCELLENT video! If you could talk just 10% slower my comprehension would increase by 70%. As a retired aircraft mechanic school instructor I would have used your videos were they available.

[@panza.]

Finnish word tarkka as accurate.