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Old 05-06-2011, 03:21 PM   #1
muibubbles
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Default finishing edges of sheet metal: other then hem roll

I need some help. im new to sheet metal and im looking for a way to finish my edges of my chair (sorry, for more of my chair project). (the shell portion where the seat cushion is recessed in)

I finally figured out a way to roll the edges with the tools i have now but im looking for a more precise way..

right now i just leave excess material ~.5" and then use the brake to bend as far as it goes then use a vice to finish off the bend. the results of the nice round edge is exactly what i was looking for but the method needs some improvements. I also need to bend the metal perpendicular to the edge so I end up with a kink. my only idea to fix this is to cut a little triangle portion out and then weld it after so the seat fabric doesnt get caught. any other suggestions?

Ive also looked into the hem roll die for a bead roller but the cost of those machines are a bit pricey just this minimal task... also in the videos ive seen, it seems to "roll" the sheet metal as well... i need my sheet to stay flat...

(do all bead rolls accept the same dies? or are theyre various sizes depend company?)

some pics of some sample pieces i did...



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Old 05-07-2011, 01:58 PM   #2
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Default Re: finishing edges of sheet metal: other then hem roll

bump!
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Old 05-07-2011, 03:28 PM   #3
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Default Re: finishing edges of sheet metal: other then hem roll

Wonder how punching a hole in the edge before forming the edge would work. It might help the metal shrink and not kink.
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Old 05-07-2011, 09:05 PM   #4
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Default Re: finishing edges of sheet metal: other then hem roll

^^^^^^^^^^^^^^^^^^^^^^^
What he said!

You need to notch the hem before you fold it, other either a hole or cutting a triangle of metal out of it so the brake cant crunch it.
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Old 05-08-2011, 12:31 AM   #5
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Default Re: finishing edges of sheet metal: other then hem roll

Look over every individual area on that piece, and think about where the metal HAS TO MOVE TO for the shapes you want to make.
When metal puckers like that, it's because the space it occupies is shrinking, and you now have excess metal that needs to be shrunk or removed.

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Old 05-08-2011, 12:38 AM   #6
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Default Re: finishing edges of sheet metal: other then hem roll

weld a piece of small tubing to the edge

form the lip around a piece of small rod
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Old 05-08-2011, 12:47 AM   #7
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Default Re: finishing edges of sheet metal: other then hem roll

You need to cut a relief in the hem (before folding the hem) where the bend will be or it will kink every time. A general rule of thumb is to make a slot that's equal in width to the thickness of the material that you are bending.
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Old 05-08-2011, 10:54 AM   #8
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Default Re: finishing edges of sheet metal: other then hem roll

Bead rollers and other edge-turning machines do a nice job, but are mostly used for radiused pieces, not straight edges. The various edge-turning dies will not interchange with other brands of edge-former machines. There are different brands and types of machines requiring multiple different dies for each one. The old catalog images below show some edge-former tools. In the upper left, you will see 5 different sets of dies for one machine, but this is only a sampling of many available die sets.


The other answers you received about needing to cut a notch at the bending point are right on, but there are variables, depending on WHY you are forming that edge in the first place. In other words, if you are just making a rolled edge to eliminate burrs, that's one thing. But if you need a "beaded" edge to add strength, then cutting a relief might defeat your purpose. How heavy a gage of steel are you working with? What are you fabricating? Will it be welded together?

There are a hundred ways to form edges, depending on your purpose, your skills, experience, equipment, and material you are working with.

I don't mean to be vague, but when I was still bending tin for a living, we had a couple of workstations with multiple "Pexto machines" (which is what we usually called them, after the name of a popular manufacturer of them). We must have had about 6 or 8 different machines, with different throat depths, angled foot plates, different gage capacity, etc, etc. We kept different dies on several tools, so we could quickly move from one to the other to progressively form the edges we required. There is a knack to it, which comes with experience, of course.

But to be honest, most of the time we just hemmed an edge, and bent it as needed, and didn't worry about the inevitable little kink. We were usually building industrial stuff and/or duct work, and it didn't matter...especially with light gage steel. If you are building something in which the appearance is important, then take the time to pre-notch the bend spot before you first bend it to form the edge. And, if strength is important, then weld it afterwards.

Good luck.
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Old 05-08-2011, 11:20 AM   #9
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Default Re: finishing edges of sheet metal: other then hem roll

if you have a local CC that teaches hvac, take a class in building ductwork
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Old 05-08-2011, 11:27 AM   #10
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Default Re: finishing edges of sheet metal: other then hem roll

i seem to recall you being in design school and am wondering what's up with your instructors. is fabrication slightly beyond the parameters of the program?
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Old 05-08-2011, 06:04 PM   #11
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Default Re: finishing edges of sheet metal: other then hem roll

come on over to metalmeet.com and post your dillemma
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Old 05-11-2011, 02:50 PM   #12
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Default Re: finishing edges of sheet metal: other then hem roll

Thanks guys my next test will be with the "v" cut out and ill weld/grind down the seam between them...

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if you have a local CC that teaches hvac, take a class in building ductwork
thanks for the tip, ill look into that.. im assuming there are a lot of tips and tricks from hvac that i can carry over to other sheet metal designs?

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i seem to recall you being in design school and am wondering what's up with your instructors. is fabrication slightly beyond the parameters of the program?
yeah. its industrial design. we learn basic model making... not much past chipboard, foam, 3d printing and some casting... I'm just more heavily interested in the fabrication portion so i'm always looking for new materials to try out. so majority i learn on my own, but its very beneficial as i feel im ahead of my classmates when it comes to actually making the physical stuff.

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come on over to metalmeet.com and post your dillemma
will do thanks for the link!
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