I have a 42" disc of .060" stainless (exact ...

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GeorgeGaskill
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I have a 42" disc of .060" stainless (exact ...

Post by GeorgeGaskill » Fri Sep 17, 2004 2:19 am

alloy not known) that we are making into a pseudo-Chinese gong. The edge needs to bent over 90º all the way around. Any ideas on how to do this? Is this possible with this material ?

Thanks.

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Re: I have a 42" disc of .060" stainless (exact ...

Post by Bryan » Fri Sep 17, 2004 10:43 am

This operation is done when making tops and bottoms of wine vats...

It is done with a pair of rollers (approx 6" dia by 1" wide) that have a radius on the edge... a horizontal roller (vertical shaft) is powered from below to rotate the disc, and also supports the disc, while a movable vertical roller (horizontal shaft) is lowered down past the OD of the powered roller to bend the lip over...
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GeorgeGaskill
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So it might be practical to do it by hand ...

Post by GeorgeGaskill » Fri Sep 17, 2004 1:34 pm

with hammer and anvil?

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Ries
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Re: I have a 42" disc of .060" stainless (exact ..

Post by Ries » Fri Sep 17, 2004 2:01 pm

There are a variety of ways to do this- the problem is, you are shrinking the metal, and with stainless, that isnt the easiest thing to do.
First, I would anneal it- is it 304? Because 3 series stainless can be annealed by heating to red, then quenching in water. I know this is counterintuitive, because this hardens carbon steel, but believe me, it makes 3 series more easily workable.

By hand, you could do it with a hammer, and some sort of curved dolly- the dolly, or stake, radius, needs to match your desired radius. You want to go around and around, moving it a little at a time, not all at once.

By machine, a pexto or niagra rotary machine will do this quite handily- these are hand crank machines, made to the same design since before 1900, so they are often available used for a couple hundred bucks, or new from jet, tennsmith, or roper whitney, for maybe 500. Roper whitney sells replacement rolls in a wide variety of profiles. You would want either a set of turning rolls, for a rounded corner, or a set of burring rolls, for a sharp corner.

Many small sheet metal shops can do this for you, quick and cheap.

The other thing you could do, is make a hammerform- this is described in Ron Fourniers excellent book, "metal fabricators handbook" by hp books- about 20 bucks, and well worth it. He also covers hand hammering, and using sheet metal machines.

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Steve_in_Mich
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Re: I have a 42" disc of .060" stainless (exact ...

Post by Steve_in_Mich » Fri Sep 17, 2004 3:08 pm

George, I'm curious as to why you want the 90 lip? (safety, better sound, looks???) and how deep a lip you are aiming for? I use to have a Lockformer power flanger that was rated 16 gage but it wouldn't do much on 0.060" SS except chew it up trying. If you have a sheetmetal shop local to you that has a 12 gage machine - maybe but it would be limited to ~ 3/4" flange as I recall.

Before I would attempt it by hand (hammer and anvil) - well it hurts to think of all the ways I'd try first to avoid that, I'm lazy. [img]/ubb/images/graemlins/smile.gif"%20alt="[/img]
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Re: I have a 42" disc of .060" stainless (exact ...

Post by Jacin » Fri Sep 17, 2004 3:38 pm

Sounds like a good job for a pullmax type nibbler to me. [img]/ubb/images/graemlins/grin.gif"%20alt="[/img]

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Re: safety, better sound, looks?

Post by GeorgeGaskill » Fri Sep 17, 2004 5:30 pm

Looks for starters. I don't know how it would effect the sound although traditional chau gongs have the lip. Safety is good also as it will be installed in a juvenile detention facility.

The project is the idea of a lady friend who is in charge of one of the dormitories. They are assigned the country China and are to present a project related to the country (no, I didn't suggest they make a lathe from 2x4's and bailing wire :-) .) It is preferred that the residents do as much work as possible (and also to spend as little as possible) so I would prefer giving them a 12" piece of 6" round as an anvil and a few 4 lb hammers. It would be good to have a blacksmith type around for guidance but that may or may not be practical. Not sure how possible a fire would be.

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Re: safety, better sound, looks?

Post by Steve_in_Mich » Fri Sep 17, 2004 10:25 pm

Just to toss out a couple of ideas;
1. Roll a strip of SS and weld/silver solder as you wrap it around the outside of the 62" circular piece.
2. Roll a piece of SS/copper/thin wall conduit/tubing, slit it on the ID (0.060" slitting saw in the mill), wrap it around the 62" circle edge and weld/Silver Solder or whatever is appropriate.
3. Attach 1 or 2 "C" clamps and with some rope hang the sheet to test what noise you can generate with different type gongs. For the actual application welded chain/cable might be better for hanging it and also attaching the gong so neither is used as a weapon by the residents.
4. If you use the sheet flat (no bent edge) bandsaw blade tooth protector (plastic channel) makes a good edge protector with a bit of clear RTV silicone to keep it in place or to get everyone involved pass out sandpaper and have them smooth the edge for safety.

I've run out of ideas. I'm glad it is your project and not mine. By george (pun), I'm sure of that. I do want to see photos of the finished article. [img]/ubb/images/graemlins/wink.gif"%20alt="[/img] [img]/ubb/images/graemlins/smile.gif"%20alt="[/img] [img]/ubb/images/graemlins/smirk.gif"%20alt="[/img]
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GeorgeGaskill
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Current plan is for it to look something ...

Post by GeorgeGaskill » Fri Sep 17, 2004 10:58 pm

like this:

Image

I thought about welding the rim on but decided not to. We'll see what happens because the detainees are not allowed anything that might disappear to become a weapon.

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Re: Current plan is for it to look something ...

Post by willjordan » Mon Sep 20, 2004 3:37 pm

As long as you have the labor, working it with hammers actually may be the best bet. I would suggest using a hardwood block rather than a metal anvil. The process of working the edge will round the edge of the block and give a gentler transition between the body and the rim.

For dishing the main surface of the gong, I'd use an endgrain block, and possibly even hollow it out beforehand. Alternatively, you could use leather sandbag.

I'm not certain why you chose stainless; for me that would be the last choice for a gong. Not very interenting in appearance and presents a number of dificulties in working. I'd probably go for just a plain old sheet of carbon steel (actually, I'd prefer a bronze, but cost may be prohibitive.)

I'm also not certain about the behavior of ss for ringing, but a great deal of that will be worked out in the forming. The dish of the surface sets up some of the tonality of the gong; the turning of the edge affects the sound; and the material itself makes a difference as well. You might want to make a smaller gong to see if it will work at all. The pitch will be higher, but it will either ring or it won't.

Best of luck on the project.
grace & peace
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GeorgeGaskill
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Even flat it has a gong-like sound when ...

Post by GeorgeGaskill » Thu Sep 23, 2004 2:44 am

hit with an appropriate mallet. The particular piece was chosen for availability and price; it was a piece of surplus material. Traditional ones are cast bronze but time and expense rule that out. Also, it will be hung outside so plain steel seemed a poor choice. The main benefit of the project is making it, so if it is not of symphonic quality, that will be soon forgotten whereas the pictures will remain. Worst part of the project is it needs to be finished Monday next, so there is no time for trials or experiments.

I will check my wood pile for a suitable piece to use as an "anvil."

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Re: Even flat it has a gong-like sound when ...

Post by Steve_in_Mich » Thu Sep 23, 2004 10:25 am

Good plan, excellent place to find an anvil and a tight but doable time table. By George I expect you will be successful again. Yes! Yes! Yes!

BTW, I wish I had thought to mention looking here earlier, oh well.
http://images.google.com/images?q=gong& ... gle+Search
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