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

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

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 !!

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

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

This video shows the theory behind making 90 degree bends. Here are links to more. For info on non-90 degree bends, see ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-PnhpJAVVasg.html. To see example calculations done by hand, see ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-WH2u43UpoPo.html and ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-VJmCP9FwJAs.html. To see non-90 degree examples, see ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-AjHw_2cfBqw.html and ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-MO5Qre9rd6o.html. To see the bends made in the shop, view ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-vDWYzAdRjGU.html. To see the same bends made in the shop without the math, view ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-I8zMdb8LrPc.html.

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

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

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.

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!!

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

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.

Absolutely excellent explanation with great analogies.

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

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

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

Thank you So much. So far the best Bend video on RU-vid. 😊

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

Thanks for all the videos you have made for AMT instruction.

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!

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.

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

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

I took Sheet Metal one year ago and I’m testing for my Airframe O&P this Saturday. Thanks man!

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

Helped a lot to understand the differences 👌🏻

Your explanation is outstanding 👍

best presentation i have ever seen

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

great presentation with application !!!

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

Thank you sir, this video is VERY helpful

Great video for concept...thank you sir..

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

This was very informative. Thank you

thanks helped so much in my project

Awesome video. Thank you!

Thanks. Great video!

Wonderful knowledge of sheet metal

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

My bend deduction formula for all materials and 90degree bends is 0.434(3MT + R) its always worked for me and never gotten me in trouble. I derived it the same way he explained in the video and I confidently would allow anyone to use it.

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

Super job - thank you.

Indeed,, thank you very much sir.

Very usefull video, thank you very much.

Good work buddy!

Sir, excellent explanation..👏👏 we need teachers like you in India..one with actual experience

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!

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

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

Nice work brother man

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

Wow, thank you so much sir 🙏

Thanks brother more understanding

This is fantastic.

GREAATT JOB! THANKS FOR THISS!

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

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

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.

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

absolutely tremendous

i like your teaching style. thanks!

Great video. I Need to convert to mm now.

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!

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.

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

Such great detail, put really well.

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

what is the thickness and bend radius did you consider?

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.

Draw the part profile from the side in CAD, then offset 45% through the metal from the inside bend radius's, then add arc lengths and flat lengths together.

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

It's good to have plenty of scrap stock to quadruple check your backstop, die placement, travel, cleanliness. Sooo many variables have to be just right to have an unremarkable perfect part. Practice on scrap to lessen waste and take notes.

Yep makes sense

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

Is this Power Point file available for reference?

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

Good sir

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) ????

Nice

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

How did you come up with 0.165 set back?

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?

Good

How did he achieve .702 value in bending allowance?

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?

How do you know bend radius . Got set back

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.

how to find k factor?

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?

thanks sir....it's helps me....but I didn't understood that sight lines

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

Is this applicable for 130 degrees bend?

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

How to control K factor on production ?

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?

How about calculating angles different from90?

can anyone explain how did he get setback as 0.165 at 11:22

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

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