Pyro-related: Any sheet metal guys out there?

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Lloyd
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Pyro-related: Any sheet metal guys out there?

Post by Lloyd »

I own a small finger brake, but I am surely no sheet metal guy!

I'm making a powder chute that must fit closely into an existing space.

Material is 0.030" #304 stainless steel. I can adjust the bend radius from about 0.020" to about 0.080" at will.

From an on-line calculator, I've determined my bend deduction for any two legs to be about 0.0755" with a 0.080" inside radius.

(Figuring K-factor of 0.4 which is also meaningless to me... never encountered the term before, but another table gave me that figure).

Can someone help confirm my guestimate, before I wreck some VERY expensive mirror-finished stock?
Thanks,
Lloyd
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Pyro-Gear
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Re: Pyro-related: Any sheet metal guys out there?

Post by Pyro-Gear »

Lloyd can you tell me the what the shape of the chute is, also is your valuable polished sheet protected with wrap.

Forgot to say the K factor is related to an over bend needed, this is due to the material being bent encounters compression on the upper surface and what you could say decompression or stretch on the lower surface.
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Re: Pyro-related: Any sheet metal guys out there?

Post by Lloyd »

It is rectangular, measuring 2.625" x 3.875" (outside), shiny mill finish on one surface, and mirror finish on the other; protected by a vinyl tear-off sheet.

About 12" long.

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Re: Pyro-related: Any sheet metal guys out there?

Post by Pyro-Gear »

I was going to post a rather long tutorial but this says it all http://sheetmetal.me/formulas-and-funct ... allowance/
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Re: Pyro-related: Any sheet metal guys out there?

Post by Lloyd »

Heh! That's where I GOT my information! <G>

I guess it's accurate????

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Re: Pyro-related: Any sheet metal guys out there?

Post by Lloyd »

Ken,
I got it done on my little ShopFox 24" finger brake! ONE PIECE, four bends.

I tossed about all night last night, and finally came up with a strategy I hoped would work, and it did.

It comes at a cost of putting a bow in one of the short sides that must be straightened after the brake work. But it was a nice smooth bow, and easy to re-form after the rest was done. Since it's not a cosmetic part, any insufficient or marring effort there didn't matter.

The production piece was a 2.625" x 3.75" rectangular box by 12" tall...

Attached, a photo of the first trial bends, to confirm the strategy. The short side is just because my scrap was too small to finish, but it didn't matter.
DSCN1482.JPG
Then, the production piece, with the liner sheet still in place. Must glue and rivet it first, before tearing out the sheet. That's a 6" machinist's rule on top for size reference.
DSCN1483.JPG
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sambo
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Re: Pyro-related: Any sheet metal guys out there?

Post by sambo »

Lloyd I gotta say I just love seeing pictures of folks makin' stuff !
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Re: Pyro-related: Any sheet metal guys out there?

Post by Lloyd »

Well, I'd not even have posted it, but it IS a "pyro" tool... so... <G>

Glad you liked it. I sure did, especially after THREE sheet metal shops within 30 miles of me said, "Impossible. It has to be made from two parts, TIG'd together." And they wanted a week. I needed it in two days.

I _guarantee_ that on the next trip to town, I'm going to show them the picture (if I don't still have the piece in-hand!)!

Fun stuff. It's the stuff pyro experimenters are made from!

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Re: Pyro-related: Any sheet metal guys out there?

Post by Pyro-Gear »

Congratulations and a big pat on the back from me well done, never say never sure if you stick at it you will win kudos.
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Re: Pyro-related: Any sheet metal guys out there?

Post by Pyro-Gear »

One question Lloyd how do you intend to finish off the joint, looking at the overlap I would say a glue job?
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Re: Pyro-related: Any sheet metal guys out there?

Post by Lloyd »

Glue first, Ken. I used an automotive silicone gasket-maker. Sanded up the surfaces, and solvent-cleaned them. Then glued and clamped for two days.

Then, while still clamped-up, I drilled for and installed three small rivets in order to take the strain off the glue joint (just in case). This thing will deliberately be vibrated pretty hard, so I didn't want to take the chance of it's springing open from the stresses.

It fits just fine in the hopper (1/16" clear all-around), and I'll be able to finish mounting it before the fireworks start tonight!

Lloyd
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