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  #21  
Old 09-29-2016, 03:36 PM
AllyBill AllyBill is offline
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Might be easier to begin with a piece of 45mm dia pipe and heat-shrink it over a tool.
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  #22  
Old 09-29-2016, 10:41 PM
leoitch leoitch is offline
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hi,
not sure if you've heard about doming blocks...

s-l500.jpg

they're easily available at jewellery supply stores or (last choice) on eBay.
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  #23  
Old 09-29-2016, 11:49 PM
Marc Bourget Marc Bourget is offline
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Consider a slip ring and die set-up.

I suggest this, with full awareness of the Tinman's flow forming technique,because the diameter is so small and (IIRC) the fact that you need 40 of these buggers- justifies the effort expended on the tooling.

Proper sized cavity with a lead-in radius. The flat blank piece is held close to the die by a flat ring, the ID of which is equal to the amount the radius exceeds the 2" cavity. When you use the punch to force the flat into the cavity the slip ring (not a "clamp" ring - you relieve the bottom side of the slip ring just enough so the ring, when clamped), doesn't bind the material - it allows the punch to draw material into the cavity.

As the punch forces the blank into the cavity, the blank flows over the radius and it will both stretch the center ( a little) and it will shrink the blank (probably also a little) as it's pulled over the radius.

May not do it 100% but it will be a good start.

FWIW
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  #24  
Old 09-30-2016, 05:15 AM
Futterama Futterama is offline
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Wow, I'm not used to this much feedback on my project postings on other forums, thanks to you all!

AllyBill, I'll try copper if I keep failing with the steels I have. I'll remember to anneal it. Thanks. I can also weld, but the thinnest I have tried is 0.9mm, and it was a bit tricky, that's why I'm planning on using silver solder, the high temperature type, this also works with stainless, I can't weld stainless. Shrinking a pipe, noted.

galooph, I'll make sure to post some good documentation for you if I succeed.

billfunk29, good find on McMaster, thanks, I'll keep that in mind. Can you explain what you mean by equal spaced puckers?

Charlie Myres, thanks, good advise on the acid, but I'll try to avoid putting hot metal into acid as leoitch mentioned, it could be a bit dangerous.

Ken Hosford, you suggestion is kinda what I'll try now, with the clamping of the blank.

Oldnek, good idea, but with a hard wood mandrel I can control shape and size accurately.

mark g, oversize blank, that makes perfect sense, I now understand what you mean, I haven't thought about that, thanks!

leoitch, I did see those blocks, and their price tag so I would just make something similar myself.

Marc Bourget, I might not understand all the details of your description (like what is Tinman's flow forming?), but it sounds a bit like what I'm trying to do now. I will be using a "ring", but I thought of it as a clamp ring, but I see that's no good, the material needs to be able to flow.
I guess what I refer to as a hard wood mandrel, is the same as what you refer to as punch.
What do you mean by cavity? The ball shaped cavities of a doming block?
Oh, and I don't know where you got the idea that I need 40 of these, no no, only a handful, to begin with, 4 half spheres would be sufficient.

So what I got now is a wooden punch, with OD 42mm, ball shaped in the end. Next I will be making 2 plates with a hole through, one where the punch fits, with hole ID 42.1mm (top red) and one where both the punch and material can fit (bottom blue), ID 43mm (42mm punch + 2 x 0.5mm sheets). The bottom plate rests on the hydraulic press "table", and the top plate is fastened to the bottom plate, but with spacers between to allow the blank to move between the plates.
Should the hole in the bottom plate have a rounded top edge? If so, which radius would be appropriate? Maybe this was the radius, lead-in radius, you talked about, Marc Bourget?

punch.JPG
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  #25  
Old 09-30-2016, 02:55 PM
Futterama Futterama is offline
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Did a quick test with some floor wood plates, they are too soft, they gave in halfway, and this moron just kept going, so the wrinkles made their mark on the wood punch

A friend came to aid, he has a lot of 10mm thick steel stock, and he made me 2 plates and drilled the center hole, and 4 holes for mounting them together, then he decided to tap the holes, even though I told him not to, so now there is a broken tap in one of the corner holes which I have to fix before I can use the plates, that's a job for tomorrow. Also I found some steel for making the punch in some more solid material. I'm getting there and this tool-making is fun

20160930_200629.jpg
20160930_201655.jpg
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  #26  
Old 09-30-2016, 04:00 PM
Ken Hosford Ken Hosford is offline
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YOU got it ,,,if you still have problems what you might try is in the clamp plates make a bead male and female . the depth and radius affect the flow of metal .
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  #27  
Old 09-30-2016, 07:52 PM
AllyBill AllyBill is offline
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Getting there now. You could set the job up then bring your steel to red heat before pushing it. You'd get some burning but do it quick and you'd win more than you'd lose and as you only need two pieces the tooling would last long enough.

Will
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  #28  
Old 10-01-2016, 07:44 AM
Futterama Futterama is offline
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Quote:
Originally Posted by Ken Hosford View Post
...what you might try is in the clamp plates make a bead male and female . the depth and radius affect the flow of metal .
Sorry, make what?

Quote:
Originally Posted by AllyBill View Post
You could set the job up then bring your steel to red heat before pushing it.
I will probably make the punch from steel too, so heat will not be an issue. I'll try that, thanks.
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  #29  
Old 10-01-2016, 10:01 AM
Ken Hosford Ken Hosford is offline
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Think of it as a steel O ring around the hole in clamping plates where half of the O ring is below the surface on lower and upper plate the Oring grove is wider by 2 metal thickness and thedepth deeper by 1 metal thickness. This causes metal to have to flow up and over the bump.
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  #30  
Old 10-01-2016, 02:31 PM
AllyBill AllyBill is offline
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Quote:
Originally Posted by Futterama View Post
Sorry, make what?


I will probably make the punch from steel too, so heat will not be an issue. I'll try that, thanks.
If you do that be sure to heat the punch too or it'll just suck the heat straight out of the job. Wood won't do that.

Will
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