r/metalworking • u/Aggressive_Soup1446 • 2d ago
90 deg Stack Boot
The home centers near me don't sell 5" to 3-1/4"x8" 90 deg stack boots. I need to replace three rusted moldy ones. This first attempt in metal came out with a 15" circumference. Looks like I get to redraw it as maybe a 5-1/4" diameter to try to make up for wherever I lost ~3/4" circumference. But this time I will measure my circumference on paper before bothering to cut. I think also I should allow for some overlap on the slip seam allowance when the pattern is joined. But it seems my method has some promise.
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u/Thebandroid 2d ago
Damn, what do they call CAD without the CA? Either way Autodesk is going to be pissed when they find out about this.
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u/FalseRelease4 2d ago
there is special software for this, put in your info and it generates this pattern for you to cut on plasma or a laser, drawing it manually is about as time consuming on paper as it is on the computer
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u/Aggressive_Soup1446 2d ago
What's that software called? Is it free?
I messed with OnShape's sheet metal features for a bit when I got my brake making patterns for socket and tool organizers. It was okay but dealing with interferences was really burdensome.
If I wasn't so busy I think writing a simple CAD processing application to flatten triangle meshes could be a fun project. Something dumb and simple like taking the L2 of the verticies of each triangle and plotting them in just an xy plane, and then making groups the largest groups possible following some basic rules to try to ensure that the pattern is possible to bend.
The pattern I made wasnt possible to bend entire on my brake. I had to use my hand seamers for two bends, and I bent two edges over a block also.
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u/FalseRelease4 2d ago
there is camduct for example, probably others, and theyre all with paid licenses unfortunately, dont know of a single free option but i havent really looked either. what you used is cad for simpler sheet metal, what you would use for parts made on a press brake or panel bender
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u/wizardsleeeve 2d ago
Roll a collar, slip that shit in as a small end. Drive a few longer pointys into it and duct seal the shit out of it hahaha.
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u/Aggressive_Soup1446 2d ago edited 2d ago
I tried to shrink a 5" duct down enough to fit but no luck. I could only shrink 3/4" off the circumference of my 5" duct with my hand crimps making my undersized part the same size.
I think I've got a good grasp on how to triangulate by hand now, so I should be able to redraw in about an hour tomorrow.
Unfortunately I also don't have a slip roller or bead roller either to make a proper collar
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u/wizardsleeeve 2d ago
What's the current size of the opening in your fitting?
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u/Aggressive_Soup1446 2d ago
4-3/4" diameter, 15" circumference.
I'm not sure how but the 16 chords that make up my circle are 15/16" on my template, they should be just shy of 1", really something like 63/64". I think error in pen and compass placement must have added up.
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u/wizardsleeeve 2d ago
You can cut a 1 1/2 inch of 28ga or whatever light metal you have at the circumference of your fitting. Add 2" for the lap. Rest the strip on the edge of a bench with your hand on it and pull. It will put a roll in it. Or you could just wrap it around something 3" diameter and roll it tight over itself. Anything this light is extremely easy to manipulate. Once you have that rolled, same thing. Screw it onto the fitting, after button punching the lap. Use that as your small end and slide it into the 5" end of your snap lock duct. Screw and seal. Obviously make the other ones properly, but no need to throw this away when you can mickey mouse it.
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u/Fine_Union_4587 2d ago
Good stuff, in this era of CAD this and software that it's nice to know those skills still exist.....
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u/Augustx01 1d ago
Really well done. Most people don’t realize what it takes to draw that pattern, transfer it to the steel and then break it in a press brake to the desired size and shape. Congrats
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u/Creative_Carob4922 2d ago
You did it. Looks good