AVT 206 A&P - P2 - Developing Sheet Metal Flats - The Math Behind the Bends

[@rtwg605]

Thank you!! This was a FAR better explanation than I'd gotten from my own class. I'll be watching more of your explanations.

Omg man, I can't even begin to thank you for this. I didn't go to college b/c I started developing a software product which turned into hardware as well but now I'm on a "roadblock" since I lack some very specific knowledge like this. Thank you so much man!!

[@pauljohnson1991]

Even if you went to college you'd still be here watching with the rest of us lol

[@miruu28]

Why is it so difficult to find such important info on the internet! Thank you so much.

[@remiew45]

Interesting, but you are making it too confusing for some. A much more simple formula for the length of a bend is......length = (radius x angle x 3.1416) / 180. That will give you the length of the bend in the middle of the material thickness if you use r+1/2t

[@JimBob-lz1gy]

Yeah, or Radius x 2 x Pi = Circumference, divided by 4 = arc length.

[@throngcleaver]

Many years ago, while working as a flight mechanic at a large aerospace corporation, I was tasked with building several complex parts for a flight test aircraft. The stack of drawings was daunting, with each part having multiple bends at various angles, but also multiple radii on some parts, and many of the flanges were at angles to the other flanges. Calculating non-standard angles wasn't fun, since the process at the time was to look up the setback in a table for that thickness and radius. (table was every 5°) I'd then have to do the math to extrapolate the answer for, say, a 37° angle. I knew how to calculate the bend allowance and do all the math, but it was taking too long and errors could definitely happen. I went to one of the computers in the shop, and basically put the bend formula in an Excel spreadsheet. I gave it enough places to add up to 4 bends, to make hat sections. To use it, all you have to do is type in the thickness, radius, and angle of each bend, and hit enter. It fills in all the info you need, and puts it in a drawing format with the thickness, radius, and angle of each bend in a table below the drawing. One click on the print button, and you're ready to cut your metal and head off to the press brake to bend your parts. Everyone loved it, and they are still using it today. Now I use Solidworks, but it took a bit of experimenting in the program to get the K factor correct (not .5) for aluminum correct. I knew my formula to be correct in my spreadsheet, so I drew a 1" x 1" flanged part, and kept changing the K factor until it measured within 0.0005" (half a thousandth) of what my formula said the flat pattern length should be. I've only used cornice brakes and finger brakes a few times, (A&P school mostly) but I always used a small hard square to align the sight line with the edge of the brake radius. Press brakes are where it's at though. Very nice explanation of what's going on in sheetmetal bending! Brought back a lot of memories. Thanks for sharing your expertise!

[@trmechanic]

thanks

[@TheEngineeringToolboxChannel]

Going through something similar at my company. Trying to streamline and standardize how we determine things like bend deductions, tool selection, die opening size, etc. Sheet metal bending has so many variables but once you standardize and control them it becomes much more predictable. Automated flat development processes and CNC press brakes make things a little easier too :).

[@arniespace]

I worked in sheet metal shops my whole life (retired now). I was a welder for many years and moved into calculating flat layouts for the last 13 years of my career. I did something similar but I developed my programs on a graphing calculator instead of excel. My programs would prompt for the necessary variables and then spit out all the dimensions needed to draw out the flat with autocad. We made a lot of cones and transitions so I had programs for those as well as other shapes you would come across in daily life. My cone program would calculate the chord, which was necessary to draw the flat in a CAD program, as well as all of the other information needed. The variables it prompted for where simply the two diameters and how tall the cone was. It was a lot like cheating, but I was never wrong, unless I made a really dumb mistake and entered a variable incorrectly. The variables for most other shapes where basically what are referred to here as the mold lines, plus the die radius, real world location of holes, etc. I never had to worry about sight lines, that was up to the press brake men, but they had computerized back stops, I only needed to give them the bend line and radius information. I also was responsible for nesting the parts on the sheet for laser cutting. At the end of my career we started using Solidworks, which took all the fun out of it.

[@tulsihomes]

Can you please share the formula you were using.

[@throngcleaver]

@@arniespace Great stuff! I've only designed and made a couple of cones, and they were related to bomb tails. Fun! I too, loved the challenge of it all, and really enjoyed that part of my career. The small department where I ended up making flight test components had a pair of Promecam hydraulic press brakes, one 4' and one 6'. They had DROs on their back gauges, making them super accurate. I ended up starting a business, (not related to sheetmetal fab, mostly machining) and eventually it morphed into sheet metal fab for U.S. Army helos. I had a pair of waterjets, (wish I had had a laser!) and bought a 4' Amada press brake. The hole location tolerances were 0.002", meaning that the center of the hole had to be inside a 0.002" circle. I put all the holes in the flat pattern full size, and once cut, deburred, countersunk for rivets, and bent, all the pieces Clecoed together and the rivets fit perfectly. (They also got conversion coated and primered, and a few got anodized black) Gotta love technology, at least for production parts. :D Saved a TON of labor. While I do love Solidworks, it sure took the fun out of figuring out the really difficult pieces. At least that knowledge got me retired at 46. I truly was lucky that I chose being an A&P as my career. Edited, because I forgot to mention, that in my spreadsheet, the little drawing included the 4 bend lines, (even if you only had one bend.......everything else would be zero) and also the material thickness, part number, bend angle, radius of each bend, and leg length, so you could mike the flanges without having to have the actual drawing at the brake.

[@kfsrayjay7898]

thank you so much!! Explained it better than my teachers did!

[@1donagin]

This video shows the theory behind making 90 degree bends. Here are links to more. For info on non-90 degree bends, see kzbin.info/www/bejne/hp_LoX13i7uUqck. To see example calculations done by hand, see kzbin.info/www/bejne/jXmVpmdpitWihtE and kzbin.info/www/bejne/jHvQdINve9x9d9U. To see non-90 degree examples, see kzbin.info/www/bejne/d5urqJJomMt1p9k and kzbin.info/www/bejne/g4CYgqWbbteXbNE. To see the bends made in the shop, view kzbin.info/www/bejne/rHW6iq13mbedfbc. To see the same bends made in the shop without the math, view kzbin.info/www/bejne/f2ndfpeYbbGlhsU.

[@paulmanhart4481]

This is exactly what I’ve been looking for. Thanks.

[@naboulsikhalid7763]

great explanation, without a word. thank you for sharing your experiences and knowledge.

[@baklolHai]

It's good to see this video . Useful for an engineer

[@nyronm941]

Best explanation available love how simple you made it, great job !!!!!

[@TheEngineeringToolboxChannel]

nyron matton agreed he did a great job!

[@tjvanderloop1686]

Great sheet metal "Bend Allowance" based on thickness and MATH...Great Job! Thomas J. Vanderloop, Author, Technology Instructor & Manufacturing Consultant; CMfgE & LSME

[@ZimmMr]

Thank you sir, this video is VERY helpful

[@pramodkinge8225]

Thanks a lot for all of this knowlegde..looking forward to see more like this..!!

[@racinford1]

I ran a Amada Turret press for years and would get programs for new development and blank and punch the holes and shapes in the flat. I had to inspect the blank and all the hole locations plus other cutouts to a drawing that only showed you the completed formed part. Being able to calculate all the bend allowances made me look like a genius . Its not that hard.

[@badboybootz8]

Taking my O&P soon and this just scared the hell out of me lol

[@rgsparber1]

Excellent tutorial. I followed it very closely and found the following minor inconsistencies: At 7:02 you imply that the material thickness is 0.032 but at 11:20 you only get 0.165 if the MT is 0.040. At 15:40 you say "inner ones" as in the inner tangent lines but the diagram shows you are using the outer tangent lines. The text is consistent with the diagram. At 9:41 you say the actual neutral axis is at 0.455 but the equation says it is 0.447. As I said, I followed very closely. Thanks for the education!

[@PG-qm5nk]

Yes I agree, some big holes is his examples . I cant quite follow where he's pulling these numbers from?

[@thestralsound]

I'm not exactly on time here, and I may lack context, but where are the 1.57 and 0.702 used to calculate the BA coming from?

[@nived3211]

Info not given.

[@TheZerosteel]

i think he never said it explicityl but MT is 0.040 and BR is .125

[@atalowais]

Helped a lot to understand the differences 👌🏻

[@rookie147]

So much theoretical and real world switchbacks I forgot if I existed

[@TheEngineeringToolboxChannel]

HAHA....if everything is controlled properly theoretical values and real world values should closely align ;)

[@lazertroll702]

yeah, it gave me flashbacks of anime filler; i was loosing track of what was 'canon' ...

[@jacobmassengill1553]

fascinating how much the bend allowances of glass and metal feel familiar. Ice only blown Boro glass though

[@sanjay052]

How did he achieve .702 value in bending allowance?

[@bkkunalsharma233]

Wonderful knowledge of sheet metal

[@malcolmhodgson7540]

Such great detail, put really well.

[@jeffchisamore1556]

You totally made this easier to understand. I punch flats on a turret and often have to calculate bends out of the drawings. Good video. Totally worth watching.

[@Mrsvetsare]

wow so complicated you make this

[@felixvincent643]

I didn't quite get how he got to the .702 value. Is this a constant? It must have something to do with the K factor?

[@floryedable]

I think he messed up. It should be 1.57* BR + .455*MT...where 1.57 is 1/4 the circumference, and .455 is the K-factor ( I believe he said he was using for Alum), and I come up with .19625+.00728 = 0.20353, NOT 0.224

[@MeetJohnnyNg]

@@floryedable what is the material thickness for aluminum?

[@jeffreymathews245]

I still don’t understand how you get .702, please explain further.

[@sethgecko1972]

Good work buddy!

[@nathanmcmahon9243]

Where do you get the minimum safe bend chart, particularly A36 Circular Rod? Is it an ASTM, ASME, etc.? Thanks.

[@swamihuman9395]

Excellent, simple explanation. Thx. BTW, I design in Autodesk Fusion 360 which supports sheet metal modeling.

[@lewisngeno4789]

thanks helped so much in my project

[@willw.birnie8446]

Keep it complicated! This is exactly what I have been looking for! Thank you so much. Keep up the great work!

[@wealthyboyrr5410]

Excellent and after all i am able to learn bending from a practical point of view. Also the buzzword "K" factor, i searched many websites and difficult to figure out how they arrived this factor and now i am clear. If possible put up a video how this K factor is found out for different materials, becoz we have whole lot of tables around the internet but unable to find how it arrived. Thanks a lot

[@1donagin]

The problem with K factor is that the same term is used to refer to different things. In many industries, K factor refers to the location of the neutral axis as a percentage. (Example K factor of .45 would be a neutral axis at 45 percent of the thickness of the material.) My example are from aviation, and the USA's FAA uses K factor to refer to the adjustment of the setback for various angles that are not 90 - so this is what you will see in my videos.

[@wealthyboyrr5410]

Thankyou don. i saw u r example video and found some website with K factor tables and arriving methods. They are for general purpose application. Thank you, u made bending theory simple when i am confused with CAD tools and now realized that hands on calculation and understanding of the fundamental theory with difference to real world case is important for design and made simple by u. Keep your work "DON" many like me will learn and follow u r teaching. Thank u

[@robert6106]

That right there is why the rest of the world works in millimetres, all that maths and your eyeballing it. That a side good stuff, in real life learning, lift from the scrap bin and check the radius from your tooling, make a chart with your tooling displaying the set back for radius, thickness, angle and so on. Do that for each tool and material thickness and you will not have to do any maths at all.

[@josafabass9670]

I´d like say, thank you so much, your explanation help me a lot, I was worried about bend but your video take my questions away

[@DennisZIyanChen]

Take the concept to a deeper first principle level, and everything is super simple. All really rudimentary stuff honestly if you just understand how metal behaves in terms of its isotropic and kinematic hardening and how the yield surface may expand or translate and why a bend radius is needed becomes really clear. First principle thinking is never about explaining the real world, but it provides a foundation that's applicable to all problem types.

[@MuckingMunt]

" if you just understand ...." "...isotropic and kinematic hardening and how the yield surface may expand or translate and why a bend radius is needed becomes really clear." I think it's this bit you assume is already in a lot of peoples education or experience already. I doubt anyone learning a trade as an apprentice would need to go off on deeper theory..... but chances are the geometry comprehension is already there from basic previous schooling or education to appreciate this video.

[@carfordelforero7122]

How about calculating angles different from90?

[@synrene]

Awesome video Did anyone catch him say '3 things' but put up 4 fingers lol

[@tuna6024]

I just caught that xD

[@lazertroll702]

that, and he threw around unit-less scalars ... reckless ..

[@Tangaroa775]

You explain it really well but your stuck in the dark ages and use imperial measurements 😂

[@Ricky123g]

GREAATT JOB! THANKS FOR THISS!

[@bearsrodshop7067]

Can't learn this kinds knowledge @ your local jr collage,,,Great presentation, and at 68+, just getting into making more parts from sheet metal & aluminum. This will be most beneficial with the cost of materials soaring everyday. thx, New subscriber as of today, Bear

[@Alex-ns8zn]

absolutely tremendous

[@ahmedekin]

Hi; 9:50 BA=1,57BR + 0,702MT you said. But π/4= 0,785 not 0,702. Which one is true?

[@adamsisson5458]

Thanks. Great video!

[@punzalmonicamaer.9054]

lods, san galing yung 0.165?

[@rajeevdabra6625]

Sir, very good explanation . But you did not tell what is material thickness (MT) in you example and from where you had taken value of bend radius (BR) ????

[@1donagin]

The example problem assumes a thickness of .040 and a bend radius of .125.

[@technofeeliak]

You've over complicated this. It's not that math isn't exact. It's that there are unknown variables. You can't perceive all the variables so you don't account for them. That's it! That's all!!!!!

[@1donagin]

Feel free to make your own video.

[@RippoZer0]

I did not know zach galifianakis could do metal bending

[@joaotexpr]

Se a teoria não bate com a realidade é porque está se usando a teoria errada. Simples assim.

[@brentlackey8316]

No theory ever said you can make a bend with no radius.

[@ummyhorse7791]

Indeed,, thank you very much sir.

[@nealblackburn8628]

i worked at a place where we did that stuff all the time but i don't remember it being that complicated, but what would i know everyone else in the comments says great job

[@AhmedXGhost007]

best presentation i have ever seen

[@NOOne-im5vg]

Sorry, you lost me at where you got your numbers from. Then you stated values that differed from the ones written down.

[@TheEngineeringToolboxChannel]

He skipped some algebra when talking about the bend allowance (BA). Do the algebra (multiply/distribute 2pi/4 to BR and .455MT) and that will give you the equation that he used.

[@swenstreed]

Very good, noticed one small error and around time mark 15:13 when you are explaining where to layout "sight line" using "bend radius" You state that you are measuring from the inside but the diagram clearly shows you are dimensioning "site line" from the outside, correct?

[@1donagin]

The site line can be measured off either bend tangent line. You pick whichever BTL you are going to put under the caul on the brake. Measure one BR towards (and in some cases past) the other BTL.

[@justinfrisbie2652]

Great information, overall Great video, however I think completing and showing the work for all of the math used would be more beneficial. But I learned alot, Thanks!

[@freemanfootball647]

How to control K factor on production ?

[@nikhildasnm2808]

Good work worth it actually can use these techniques to my projects also

[@ismaeldelgado6615]

The best explanations of where each thing comes from!!! Thankyou!!!

[@elysha1980]

I can't thank you enough for such amazing information video which you share with :)

[@prateeksharma5124]

concepts are very nicely put in a concise and interesting manner. good presentation style. thanks for uploading...

[@richardbarnes3665]

Such an excellent lesson!!!! Thank you for sharing this with us. Would you be willing to share this PowerPoint?

[@bkkunalsharma233]

Good sir

[@lostcar2312]

Great video. I Need to convert to mm now.

[@purpledude5526]

You analogy that Pacman turns at sharp corners is a bit off. Technically, if you start your turn before Pacman actually turns, he will in fact turn a very nice curve around the board. I have used this knowledge in the past to keep my patterns in time within 1/10th of a second of each board. Knowing this about Pacman and memorizing patterns for specific boards has gotten me to 9th place in the world and into the Guinness Book of World Records with a score of 3,178,060 points.

[@EstechMagnetics]

It’s more like 1/3 material thickness instead of 1/2 on the neutral axis. Metals are more encouraged to stretch than shrink, especially when the die is in static connection with the material.

[@automirrorguard8676]

I have a issue with bending m.s. sheet metal at 90 degree. Can you help.

[@PedroGomez-bd9ro]

This is a quarters worth of college crammed into a quarter of an hour

[@thepovertysoldier9220]

Ever heard of NNPTC?

[@PedroGomez-bd9ro]

@@thepovertysoldier9220 Enlighten Me

[@thepovertysoldier9220]

@@PedroGomez-bd9ro The navy sends you to Charleston SC for 1.5 years to teach fresh out of highschool sailors how to operate Nuclear reactors. It's ultra compressed.

[@MeetJohnnyNg]

How did you come up with 0.165 set back?

[@jordanhowell3870]

how does this guy know anything.

[@aminnikmehr4738]

Because he had primarily learned what he was supposed to know

[@Sterling96]

He's an A&P mechanic, and planes operate on PFM (pure fucking magic) an old instructors joke😂. But most A&P's I've met are know to be pretty handy in fixing things. Guess that's why theres still planes over 60 years old that are still flying👍

[@jordanhowell3870]

@@Sterling96 No doubt

[@D4rkS7der]

Very usefull video, thank you very much.

[@jeraldcajes7575]

Is this applicable for 130 degrees bend?

[@hulong008]

Question: BA=2pi/4 (BR+1/2 MT). means pi/2 BR + PI/4 MT. it should be 1.57 BR + 0.785 MT. Why does 0.785 change to 0.702?

[@1donagin]

9:30 to 9:45 in the video answers your question. The neutral axis is not exactly at 50% for any material I know of. You can look up the neutral axis on a chart for your material. For hardened aluminum, the nuetral axis is around 45% of the thickness. The .702 in the FAA's published aluminum bending formula comes from adjusting for this non-50% value.

[@The-PlagueDoctor]

Can you explain where the FAA's published aluminum bending formula is and how to calculate/adjust for the non-50% value? Or what the formula is? or am I missing something completely? Because 2π/4(.45MT) still = .706MT

[@TheEngineeringToolboxChannel]

​@@The-PlagueDoctor must be a typo or rounding error in the K factor value (neutral axis location)... and besides the difference between .702 and .707 in very minimal. Even in thicker .25" material the deference in BA is only .003". Since this formula is just an approximation I would say that's splitting hairs. However, I do see your point and can appreciate the need to understand the derivation fully, but his derivation is not wrong. There was just some sort of discrepancy in the K factor.

[@The-PlagueDoctor]

I appreciate the reply!

[@insylem]

Thanks for the refresher. A&P School was 12 years ago. Though, I've only ever done all that math in School. Even for my airframe test, we just guessed and bent it.

[@NoNo-dq4mc]

if you follow the algorithms needed to produce the bend allowance and consider k factors, most metals that are commonly bent will hold true within tolerance if metal grade or tolerance of thickness is followed And the machine is dialed in. I only have trouble with a few alloy as far as I have encountered.

[@zakaroonetwork777]

Thank you So much. So far the best Bend video on KZbin. 😊

[@jameshenderson3867]

Thanks brother more understanding

[@sahildharia2972]

Hey mate , I am from Mumbai University (India 🇮🇳). Thanks for this video.

[@bootasingh6342]

Halftime

[@pradipacharya6794]

I was in the middle of video and I just looked at T-shirt and saw SIU Carbondale... I am also in the same university for MS in Mechanical Engineering... Thank you for sharing knowledge

[@magedgaber7541]

from someone who's been in the service for more than 25 years in the Air Force this is by far the best explanation ever , thank you sir !!

[@scottyp.644]

Thank you. When the company wants to know the procedure for how I do what I do. I will direct them to this video. I think my job is safe. You are brilliant. Excellent explaination.

[@Hitman-ds1ei]

Yep makes sense

[@idreeskhan-zp5ey]

I wanna design v-shape die and punch for bending at 90°,please anyone tell me what should be the width and thickness of the die and punch,the inner radius,the punch force.If I choose the the dimension of the plate (to be bent) is length*width*thickness=200*30*10?

[@eddievarela5691]

This was very informative. Thank you

[@rkregers]

Thank You so much for this video! If this was in metric system units it would be priceless, lol

[@kkhushnud4178]

Nice

[@jackkb100]

what is the thickness and bend radius did you consider?

[@justinsinkala]

Nice work brother man

[@amrhussein951]

in first example how you get the value of set back to be 0.165 (or you assumed it ). thanks for great explanation

[@JaswinderSingh-mb7ki]

Hi sir, what is the source of the safe bend CHART?

[@1donagin]

The practical experience of many people. You can look up an aircraft aluminum chart in AC 43.13-1B.

[@JaswinderSingh-mb7ki]

@@1donagin can I use same for sheet metal components of automobiles.. For example brackets fenders and other body parts of vehicle?

[@1donagin]

@@JaswinderSingh-mb7ki The chart are specific to the metal, alloy, and heat treatment of the material. You need to know what steel you are using. Examples 4130, a36, etc.

[@Portrayalpress]

Super job - thank you.

[@bambumbambu]

meters! use meters not inch

[@michaelyoung698]

Aok. Now I'll be visualizing those cars and drivers each time I get my bend allowance!

[@brahimabdelsadek5815]

Thanx so much master.big respect to u.keep going

[@varunkumarshankar1192]

How do you know bend radius . Got set back

[@karanp5728]

Wow, thank you so much sir 🙏

[@r.mercado9737]

This was quite stimulating! I enjoyed this teaching very much!