Greetings all: I'd like to generate a bunch of 3 to 4" disks of sheet
metal (pretty thin, 20-ish and thinner gauge), and am looking at
punches to do the job. Would a Greenlee-type punch preserve the
structure of the punch-out (I realize its main purpose is to make the
hole, but I'm actually interested in what will be punched out)? Is
there some other method that I'm not thinking of (I figure a hole saw
is too aggressive and will leave a pretty rough product on both the
hole edge and what falls out). Any advice would be appreciated.

"fura-2" wrote in message
oups.com...
Greetings all: I'd like to generate a bunch of 3 to 4" disks of sheet
metal (pretty thin, 20-ish and thinner gauge), and am looking at
punches to do the job. Would a Greenlee-type punch preserve the
structure of the punch-out (I realize its main purpose is to make the
hole, but I'm actually interested in what will be punched out)? Is
there some other method that I'm not thinking of (I figure a hole saw
is too aggressive and will leave a pretty rough product on both the
hole edge and what falls out). Any advice would be appreciated.

Unless you use an external press there will be a hole in the middle from the
draw stud. The punch is also angled which tends to bend the piece that comes
out. I guess you could flatten a twenty gauge disk fairly easily. You would
want the old style punches, not the slug busters. What are you going to do
with the discs?

fura-2 wrote:

Greetings all: I'd like to generate a bunch of 3 to 4" disks of sheet
metal (pretty thin, 20-ish and thinner gauge), and am looking at
punches to do the job. Would a Greenlee-type punch preserve the
structure of the punch-out (I realize its main purpose is to make the
hole, but I'm actually interested in what will be punched out)? Is
there some other method that I'm not thinking of (I figure a hole saw
is too aggressive and will leave a pretty rough product on both the
hole edge and what falls out). Any advice would be appreciated.

You need a die blanking punch set and a press big enough to do the job.
You're barking up the wrong tree with any manual electrician's type punch like
Greenlee because they use central holes for a bolt.

When you want the hole sized right, the punch is the right size and the die has
clearance. When you want the blank sized right, the die is the right size and
the punch has clearance.

Another way is to use a trepanning cutter on a mill or lathe.

GWE

On 7 Sep 2005 16:48:52 -0700, the renowned "fura-2"
wrote:

Greetings all: I'd like to generate a bunch of 3 to 4" disks of sheet
metal (pretty thin, 20-ish and thinner gauge), and am looking at
punches to do the job. Would a Greenlee-type punch preserve the
structure of the punch-out (I realize its main purpose is to make the
hole, but I'm actually interested in what will be punched out)? Is
there some other method that I'm not thinking of (I figure a hole saw
is too aggressive and will leave a pretty rough product on both the
hole edge and what falls out). Any advice would be appreciated.

Greenlee punches require a drilled hole (maybe something like 1/2" for
that size, I don't recall) and they cut with a curved edge, so the
result is a rather curved slug with a fairly large hole in the middle,
probably not what you want.

If a hole in the middle is acceptable, maybe you could stack blanks
and turn them on a lathe.


Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com

I now it takes all the fun out of it but you can buy these from a
trophy/awards supply outfit like Freeman. They come in brass and
aluminum with protective paper. They are perfect circles and the edges
are smooth. Lots of sizes and finishes. Natural, shiny, blue, red,
green, white, black. I have printed thousands of these over the years.
Google for trophy supplies.
If you want to make them I would suggest a router or you could buy this
nice rotary tale I have here and bolt it to your milling machine. Good
luck
Dan

STOP!!! I punch-out thousands of 19 and other ga. disks that then become
wire wheel hubs. (round) how many, what dia. do you want a hole in the
middle?


"fura-2" wrote in message
oups.com...
Greetings all: I'd like to generate a bunch of 3 to 4" disks of sheet
metal (pretty thin, 20-ish and thinner gauge), and am looking at
punches to do the job. Would a Greenlee-type punch preserve the
structure of the punch-out (I realize its main purpose is to make the
hole, but I'm actually interested in what will be punched out)? Is
there some other method that I'm not thinking of (I figure a hole saw
is too aggressive and will leave a pretty rough product on both the
hole edge and what falls out). Any advice would be appreciated.

Thank you. I'd like to make bobeche (wax cups) out of them. I guess
bending is what I'd want to do anyway. Thanks.

You're absolutely right. There will be a hole, and I forgot to take
this into account in my post. I guess in the worst-case scenario I
could configure things so that I could fill the hole with weld (if I'm
good enough).

On 7 Sep 2005 19:16:57 -0700, the renowned "fura-2"
wrote:

Thank you. I'd like to make bobeche (wax cups) out of them. I guess
bending is what I'd want to do anyway. Thanks.

It isn't cupping, though, it's bending.

See the photo at the top of this page:
http://www.radiodaze.com/Catalog-205-page49.pdf

The slug ends up shaped just like the punch (bottom part), while the
chassis ends up flat like the die (top part).

You want to make something like this?

http://planta.ecolevs.ch/bilingue/3P...ux/Bobeche.jpg





Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com

According to fura-2 :
You're absolutely right. There will be a hole, and I forgot to take
this into account in my post. I guess in the worst-case scenario I
could configure things so that I could fill the hole with weld (if I'm
good enough).

Hmm ... you *could* mount the halves of a Greenlee punch in a
hydraulic press, and punch holes without a center hole. But they
*still* would come out shaped like a Pringles artificial (reconstituted)
potato chip. :-)

Enjoy,
DoN.

--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

Thanks very much for the links. The punch is indeed what I was
inquiring about, but as has been pointed out by others I guess I don't
necessarily want the hole in the middle. The detail of the bobeche
shown in your link it quite a bit greater than I really had in mind, as
I'd be happy with simply steel in various shapes.

Assuming I could weld the hole closed I don't think the hole is too
great a problem (and could even come in handy at times). I just
tinkering with metal candle holder ideas, just for projects at home.
Thanks.

Excellent idea, thanks very much for the source info.

I hear what you're saying, but maybe I could just bang 'em back to
near-flat or cupped, depending on what looks best. I've got an arbor
press -- you think that would give me enough force, esp. if I used a
pipe extension on the handle?

According to fura-2 :
I hear what you're saying, but maybe I could just bang 'em back to
near-flat or cupped, depending on what looks best. I've got an arbor
press -- you think that would give me enough force, esp. if I used a
pipe extension on the handle?

Frankly, I doubt it. (Aside from the problem of maintaining
proper alignment.) What tonnage rating of arbor press? I would not try
a 1" or larger punch with my 3-ton arbor press -- pipe extension or no.

I remember the effort I had to put onto a 1/2" drive ratchet
when punching steel relay rack bottoms with a ball-bearing screw and
grease on the threads.

And I remember breaking the drive screw on one of the 1/2"
punches. And that is one *tough* screw.

Greenlee sells a hydraulic drive for the bigger punches.

And the amount of force needed on the handles of a Weldon hand
punch with 1/4" punch and die installed -- if you are working on steel
makes me think that you would need more force for a larger punch than an
arbor press is capable of providing.

Although -- if your metal is thin enough and/or soft enough, and
the holes are small enough, *maybe* you can get away with it. Make sure
that the die is firmly mounted on the anvil, and that the punch does not
wiggle far enough to the sides to contact the edges of the die.

Maybe make a fixture to hold the two parts with guide rods and
springs to pull the punch back out of the die and the sheet of metal
stock which you are using. (But this is pretty close to what you need
for a punch and die which will give you flat workpieces.)

Good Luck,
DoN.
--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

Yeah, I suspected as much (I've a pretty small arbor press) -- time to
consider a hydraulic one I guess . Thanks for the tips.