#31
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Quote:
A plastic apron and gloves and some eye protection is wise, but I have been doing it for over 30 years without any issues. The beauty of the method is that it saves a lot of mechanical cleaning. I like the progress you have made so far! Cheers Charlie |
#32
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Cut the blank into a circle and try it again.
You have to much metal around. Ben |
#33
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Thanks, I actually wondered if it makes a difference whether the blank is square or round. I'll cut the next one round and use stronger plates that doesn't break.
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Martin |
#34
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Some progress. Got some really hard wood floor planks from my father and tried those. They worked better but still gave in.
The blank is OD 120mm. The wood punch survived the abuse. Wood plates prepared: DSCF4213.jpg Rounded edge on the lower plate: DSCF4214.jpg Spacers, total of 0.8mm: DSCF4215.jpg The blank on the lower plate: DSCF4216.jpg Refurbished wood punch (reused the one with the marks): DSCF4217.jpg Top plate mounted, blank in place between plates: DSCF4218.jpg Bottom side of the plates with countersunk bolts: DSCF4219.jpg All set up in the press: DSCF4222.jpg The lower plate broke at 2t (4000 pounds) pressure: DSCF4223.jpg Bottom view: DSCF4224.jpg Punch and top plate removed: DSCF4225.jpg The result. Now quite there yet: DSCF4226.jpg Next attempt with 10mm steel plates: DSCF4227.jpg
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Martin |
#35
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Martin, thanx for documenting your project. I'm sure i'm not the only one that learned something thru your efforts. Tom
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#36
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Thanks for posting you project. We are following your progress.(over 1,000 views!). Some clamping force/resistance may help some, watch video https://www.youtube.com/watch?v=RhG8gISbWMA
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John |
#37
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Interesting and learning as well.
The attempt with the wood plates looks like you are almost there. I'm betting that the metal plates will work for you.
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Larry |
#38
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Cut a smaller size circle
Ben |
#39
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So if I started with a too small blank, and now use a too big blank, what size blank should I use when half sphere diameter is 42mm?
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Martin |
#40
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I'd add more radius. The sharp corner forces the shrinkage to occur all in a short distance. The slip ring method (relieve the bottom side of the clamp plate so the blank will more-or-less stay flat while being (stretched and shrunk) pulled into the hole.
The radius dimension controls the relative degree of stretching and shrinking. If the radius is small, the force is also higher, making it tougher on the female forming block. FWIW
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Marc |
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