Fits and Tolerances: How to Design Stuff that Fits Together

Fits and tolerances are a foundational mechanical design skill, but they're commonly misunderstood and misused. In this video, we explain how to apply correct and functional fits and tolerances using ASME B4.1 and Machinery's Handbook, so your parts fit together exactly as you intend, the first time, every time. No emergency filing required!
Blog Post: tarkka.co/2019...
If you're looking to pick up a copy of Machinery's Handbook, don't worry about getting the latest edition. Most of the content hasn't changed in a long time. For example, ASME B4.1 hasn't been revised since 1967!
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[@BestFleetAdmiral]

Ah this is awesome! So many people just say "Yeah these are the fits and tolerances" but you guys actually showed what those fits look like, which is so important for us to connect what we want with what we have to say!

[@ryanheyman1223]

As a machinist who works constantly with engineers to make their parts, taking the time to talk to the people who make the things you design will end up saving you both time, money, and headaches.

[@pdrhodes68]

Great video. Would have liked to see examples of when to use each fit in real world designs. I had an older engineer help me out with that when I was starting out. The benefits of the loosest fit possible are many.

[@akosrupp232]

great vid

[@tardisblu3.1415]

Nice

[@JayLikesLasers]

This was excellent! Perhaps as a suggestion a video on GD&T, and another on statistical tolerance stacks and Cpk values?

[@tarkka]

Sounds like there are a few thumbs up, here and on reddit too, for GD&T, so we've added that to the list!

[@JayLikesLasers]

@@tarkka Sincerely looking forward to it. The 20 minute 'e-learning' provided at work for these sorts of things are usually so dry, and involve clicking of the 'next' button a bunch of times.

[@hammurambi]

@@JayLikesLasers Check out the GD&T Basics course. It's pretty long and it is a paid course, but it's very easy to understand

[@tarkka]

Thanks! Our next video will be position tolerance and we will do more GD&T as well. We discuss material selection for fasteners in our “Screw It!” video, and check out the companion blog post for material compatibility and strength charts. For calculating forces etc., we can do another video. I recommend getting Shigley’s Machine Design book, that has the info you need. Good luck with your career plans! We are happy to hear the videos help :)

[@augurelite]

This was infinitely more clear than my engineering lectures at school. Great video

[@lancebeasley3064]

If you are reading this, I hope today is much like a clearance fit - easy to get through, with lots of light at the end of the tunnel.

[@holyravioli5795]

How on earth did i not find this channel earlier, i've been struggling with tolerances for ages now.

[@andygraham9056]

Why is she almost whispering?

[@Bloated_Tony_Danza]

That RC3 fit was oddly satisfying

[@MartinezRBA]

Since I first started on Mechanical design this was one of the most challenging things to understand. I remember feeling incapable of imagining how these tolerances would behave beyond my CAD models. And that's why this video is so valuable. Thanks!

[@buntayaj2167]

Love the visual comparison. Seeing numbers and descriptions of "loose" or "tight" doesnt really paint the full picture.

[@Irohbro]

Then you can paint the rest yourself. And you get a shorter video.

[@sethtrey]

This is high quality content. How did you guys get so good at explaining?

[@02cahillt]

You can get a running fit with a drill if the feeds and speeds are correct.

[@thatdopelifestyle2602]

"They'll tolerate it."

[@tjvanderloop1686]

Excellent visual examples of ANSI Standard Fits. The use of shop-floor tooling examples was great! Thanks for the design and piece-part applications. T J (Tom) Vanderloop, Author, Mechanical Designer, & Consultant; ATEA, AWS & SME-Life Member & Leader

[@the7thgymleader]

Great video ! Maybe one on choice of fasteners or bearings!

[@joaonunes782]

About to say that, bearings vídeo would be allsome

[@tarkka]

We'll add bearing and fastener selection to our list. That will be a fun one! Thanks for watching!

[@sky173]

@@tarkka Love the channel. Any thought's on a bearing video yet? Love to see more!

[@effreyjeppstein4673]

Great info! Subbed! Maybe do a video on shaft seal/bushing/bearing witchcraft?

[@StuartZiane]

This is a great video, very well explained. I'd love to see an ISO version.

[@x0urce942]

tabletop machine shop made one :)

[@KentRodgman]

@@x0urce942 that one is why I found this one!

[@Happy_363]

Can you please elaborate the same in millimetre (metric system)

[@neilfranciotti1020]

True position would make a good logical next video. Great Job.

[@ALXG]

I subscribed immediately. Fantastic explanation: both informative and short.

[@lephtovermeet]

Thank you for this. I think just about any machinists, engineer, or just general builder has encountered these and has some familiarity with them, however to see them lined up next to each and visually put together is a huge help with mental approximation!

[@atul2048]

This is one of the best video I’ve seen with respect to fits and tolerance

[@inertproductionsalternate9114]

Great video! Thank you I have been trying to find resources on how to determine an acceptable level of tolerances but most fall laughably short. Yours was interesting to watch and informative.

[@rahulbindhu]

Wow, completely blown away by the quality and content of these videos.

[@OMGIndia-vd9ls]

can you pls let us know when to select what kind of fit??

[@BuddysDIY]

That lc6 looks like so much fun to play with

[@tjvanderloop1686]

Excellent Job! The Machinery's Handbook is our "Bible of the Trades" and you did well! T J (Tom) Vanderloop, Author, Technology-Instructor & Design Consultant/ AWS & SME Leader & Memberships

[@vaga4239]

KZbin algorithm taunting me trying to fit aftermarket parts on my motorcycle.

[@arturzych138]

Can someone explain to me @2:44 why the shaft is 0.4295+0.000/-0.010 while the limits are -0.008/+0.018.? Why is the shaft automatically reduced by 0.012?

[@ProfessorGreen900]

The Shaft is reduced by 0.0080 from the hole dim (as stated in the tolerance limit, which is -0.0080), so the shaft diameter becomes 0.4375-0.0080= 0.4295. Now a shaft of 0.4295 can can surely fit inside the hole of 0.4375. Now with that shaft, you can go more 0.0100 smaller (extra play) as per the tolerance limits, (difference between -0.008 and -0.018 = -0.0100).

[@arturzych138]

@@ProfessorGreen900 thanks for explaining that. Makes sense now

[@tjvanderloop1686]

The Machinery's Handbook is a great tolerance-resource. This is a great video. The graphics from "SME" identify the exponential curve that exists with the tighter tolerances. Thanks for the excellent review on tolerancing. T J (Tom) Vanderloop, Author, Technology-Instructor and Design Consultant; ATEA, AWS, & SME-Leader/Memberships

[@DanielTesla74]

An extremely helpful video if you're not a mechanical engineer. I am just an enthusiast who is designing a big thrower flashlight and needs to know the tolerance necessary for the aluminium reflector to slide into the aluminium body of the flashlight. Although this uses the US standard I could see that I need RC3 that would means space of 0.08-0.1 mm between the parts.

[@Jazu58]

Mulher faz a narração mais devagar por favor.

[@RobertWelchman]

Thank you for clarifying that! Definitely helps a lot on the design side.

[@jackroman8821]

Absolutely excellent video, great use of examples and explanations. Thank you!

[@greglaroche1753]

Very interesting. I’m subscribed and look forward to watching more videos from you.

[@rosssshed2336]

Good video. Is there an equivalent reference for positional accuracy?

[@tarkka]

This is the only one I have seen (second table on the page): www.engineersedge.com/manufacturing/drill-mechanical-tolerances.htm It appears to relate to drilled holes. As far as true position of machined features, this might be something we can test.

[@harshavardhanaharsha7261]

Can you please make vedio on difference between achieving surface finish by grinding and surface finish achieved by itself in the process of maintaining the tolerance.

[@victorvontastyfreeze5553]

Another great video. Excellent background music

[@tarkka]

Thanks!

[@leandrojr.picson58]

Tolerance is useful in mechanical design

[@emanggitulah4319]

Metric please... Only USA and some 3rd world countries using inches :facepalm:

[@WildlyStapled]

Underrated channel. Schools should play these in shop class on days when the teacher is hungover

[@MRMIKE276]

Think about how much information was provided in this video... how much would all of this information cost you at school? Probably in the hundreds especially because it wouldn't be formatted in such a nice way. KZbin creators are saints.

[@jerzykepinski]

Dear Lady! You should speak much louder, clearer and slower. The stupid music in the background adds no value to the video and makes it this much harder to understand what the Lady is talking about, so why put it there? Thumbs up for the comparison of the fits.

[@manmohanmp]

How does interference fit work- like , how does it make it permanent? what's stopping it from coming apart?

[@researchandbuild1751]

This narrator lady has a beautiful voice but it's honestly too fast and a bit hard to hear and understand

[@stevenleffanue]

Great vids and info. Would love to watch more of your vids but the female voice used speaks too fast and not easy to pick all the words.

[@yokeshkumar8323]

Nice video guys ! post videos about all types of GD&T symbols & inspection , tolerance stackup analysis in the same way !! Thank you

[@cirosmserpico3832]

Hello, the transition fit LT3 could be acceptable for a ball bearing fitting? between LT3 and press fit there are an "intermediate" fit? thank you for your patience

[@michaelrizun3403]

I would like to know why Engineers will place tolerances on a print, (example) .500+.005-0.000 ,and/or .250+0.000-.005, as to opposed stating the mean tolerance along with the acceptable tolerances. It does make for a confusing adaptation of which dimension you are measuring and what the tolerances are.

[@tarkka]

I think some engineers use this convention to more clearly convey the "design intent." To use your example, the engineer is possibly saying "I want a slip fit on a .500 pin." The problem is that some engineers (and possibly machinists) start to think that 0.5005 (very close to the nominal) is "more right" than 0.5025 (right in the middle of the tolerance band) and end up aiming for the nominal dimension. Instead, you really want to keep parts as close to the middle of the tolerance limits as possible.

[@jeepmanxj]

You can hit far tighter tolerances than your chart and explanation repeatedly with cnc equipment. I do it all day long. Interpolation on a mill is not a good way to make a round hole and anything resembling a tight tolerance you should avoid this.

[@MajesticDemonLord]

Woah.... wait a minute... You telling me that "hit it with a bigger hammer until it fits" isn't the right way?!? My whole life has been a lie.

[@wayedk1040]

So I'm working on my bachelor's in engineering and we don't get this...

[@pieterbotes8938]

This person's voice sounds like a robot. No thank you!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

[@argueve]

Great!! Very Helpful thank you so much!

[@williamhuang5329]

Hanzhen harmonic drive gear , robot arm gear , over 30 years experience

[@RicktheRecorder]

Narration is gabbled and I didn’t believe that either narrator knew anything about what he or she was reading.

[@Proximachannel]

Great video! Can you post video about metal cutting?

[@tarkka]

Sure, is there a specific topic within metal cutting you are interested in?

[@HopelessCT]

this is my new favorite channel ever

[@FNeighbor]

This is a really nice video! You just got one new subscriber! Please keep them coming!!!

[@tarkka]

Thanks!

[@NorfKhazad]

We have a part we're working on now with a .003"-.005" interference fit, a bronze bushing going into an aluminum housing. Had to heat the aluminum in an oven and chill the bronze with dry ice because the aluminum already has marking on it which can't withstand more than 200°f. That's definitely a fit that isn't intended to ever come apart.

[@andrewt8116]

All I could hear while she spoke was new shoes on a basketball court

[@intheshell35ify]

Surface finish plays a huge roll in fit.

[@johngaver1104]

This was very helpful. Thanks

[@engineerahmed7248]

Best video I've ever watched .... Plz do a video on injection moulded polymeric parts and FABRICATION PROCESS TOLERANCES too ...eg final part is made up of many machined parts welded together

[@Zippo_1234]

Good video, very nice job with demonstrating the different fits

[@tarkka]

Thanks!

[@GermanTopGameTV]

One thing about this video that doesn't quite sit right with me (maybe it's because I'm used to metric and it's different in Imperial Standarts) is the portrayal of the fits. A high tolerance doesn't mean that parts will end up having lots of clearance - it means that those that do don't go into the waste bin. The workshop will still try to match your indicated nominal diameter. They will not install special "worse" tooling to give you a nice wide range of rattly fits, they will simply not remove that many parts in quality control. Of course I am aware of the concept of intersection fits and press fits, which just mean that the parts "share" a hypothetical space, but the choice of a press fit does not influence the machining cost at all. Tolerance is the determining factor and can run any clearance fit, intersection fit and press fit into a high price range. Yes, even the loosy goosey one. You can have a +0,1 mm to +0,105 mm tolerance dimension on a bore, and that will make it quite expensive, even though it clearly is a clearance fit. Why would you need that? Maybe your part needs to keep a constant oil film on its surface that has to have a very precise volume and flow properties. Just keep that in mind. The choice of tolerance is the thing that makes the accountants angry, not the choice of clearance, intersection or press fit.

[@BLACK-hl4ic]

Summary 1. Clearance Fit - Shaft Max OD less than Bore Min ID 2. Transition Fit - Shaft max od greater than bore min id but shaft min od is less than bore min id. Bore max id is more than shafts max od. 3. Interference Fit - shafts min od is greater than bore max id

[@swamihuman9395]

Excellent! Thx, a lot. BTW, have a EE degree, but find myself doing a lot of mechanical design/CAD/prototyping (at local makerspace; for members, and clients), so have been on a practical, and self-academic path. Really enjoying the endeavor:)...

[@rc8rsracer1]

Rc6 can be repeated using a drill just under the finish diameter repeatedly. I’ve cheated 1” reamed holes using a 63/64” bit then finishing with a 1” bit using a .007” feed. Gotta do what ya gotta do

[@lortunder]

just found you guys! WOW THANK YOU FROM THE BOTTOM OF MY SCRAP PILE (which is where my heart is)

[@dansv1]

There are so many KZbin channels, Tom Stanton, Lock Picking Lawyer, Adam Savage, to name just three, that improperly use the word tolerance to mean clearance. As a retired machinist, it drives me nuts. I always leave comments trying to inform them, but to no avail.

[@camilewis87]

Do you think you guys could do a video on the types of engineers a company would be hiring for and what their job description might be? I am asking as someone who has worked in manufacturing for over 10 years and has been a CNC programmer/ machinist for the past 8. I have been thinking about going back to school but am still not exactly sure what to go back to school for. I just know I am ready to move up in my career. Great videos and thank you!

[@nikonurknees255]

how much clearance is on an rc6 fit?

[@thomastoadally]

Good explanation of making a pin fit. I understand your language, been a machinist for over 40 years. Good luck with your channel 👍

[@aakashgupta4702]

Please make video on GD & T detailed one.

[@davestambaugh7282]

You mean the software manual does not explain fits and clearances? I am flabergasted that it does not. Always remember that two objects can not occupy the same space at the same time. I like the way they tolerance cylinderical fits with plus plus, minus minus instead of plus a value minus nothing. It insures that you will always have some clearance.

[@mikebeta2909]

Hey guys, Thank you for the video, very informative. I have a question to ask: how can I compensate on tolerances when the assembly has 4 parts stacked up that their thickness may vary. thank you

[@JohnyDays69]

THIS IS THE MOST EDUCATIONAL VIDEO I HAVE EVER WATCHED ABOUT METAL PARTS. - EXCELLENT AND THANSK FOR SHARING KNOWLEDGE...!

[@ThriftMedusa]

Great explanation , could you guys also make one for how to choose GD&T tolerances ( type of tolerances & it's numeric values)

[@yyyyy354]

This. I always wonder how they're made. Nice explanation

[@FenomeSean]

This video is great. Its all fun on the computer like you say but I'd pay some money for a set of ANSI pin and hole fitments just to get a real world idea.

[@raminmersi]

Thank you for this great video. It was really helpful.

[@MrZhefish]

topic idea: machine tool inspection, the different methods used for ways like dovetails, linear rails and the system to actuate like pneumatic, trapezoidal screw, ball screw - and how to check for wear and alignment, backlash and what to do :-) could be a mini series, like the tolerance classes of lead screws and off the shelve parts, preloads etc.

[@karlsangree4679]

I've watched a couple videos that try to explain limits and fits, but this was the one that caused me to have an "Ah ha!" moment. Thanks!

[@brajaybr]

I'm so thankful for sharing this video. Gave a great deal of information on connecting the theeory to the practical application!

[@rabbitbabbit7311]

Can you guys make a video series on GD&T? Or a example of engineering and designing a component?

[@anneallison6402]

Could you talk about different machines?

[@foolwise4703]

That is a really nice video. Its too bad its imperial so I will never use those terms, but you demonstrated the concept really nicely.

[@Andronicus1717]

Another great video. Does anyone know where one can get a set of parts to demonstrate fit classes? I always recommend new engineers keep a set of calipers and feeler gauges at their desk to help visualize specified tolerances. A set of class of fit demonstrators would be another fantastic learning tool to keep handy.

[@MrSingh369]

Thanks to KZbin for suggesting this video and also Thanks to tarkka

[@davidschwartz5127]

Too fast, try not drinking that extra cup of coffee before the camera light goes red.

[@mguarin912]

These videos are gold for the amateur engineer (like moi). Thanks!

[@Julian_Fitzek]

There are some things wrong here...

[@sovietoperator1385]

Конструктор: ставит 11-12 квалитет Технолог: видит 14-ый квалитет

[@brycecroucher9944]

Hi there, thank you for the insightful video! After watching, I'm left wondering how you design the strength of your interference fit. If for instance you want to calculate the press force required for installation, or the torque that can be transmitted by the interaction. I'm also curious when a retaining compound would be used, and how that would affect the calculations.

[@shashankmore45]

Inches is the problem.

[@kaapotzu]

Great video! Hienosti tehty video! Ihmetyttää tuo Tarkka nimi...?

[@Xsidon]

it feels like christmass thank you fior this in depth and easy to understand video