I think that this is a simple question, but I don't know the answer. I
am sure that a die maker would know the answer, and probably other folks
as well.

I want to make a simple male and female die for forming sheet metal.
The sheet metal is 0.040 inch (1 mm) thick.

The male die would be a piece of 1/2 inch (13 mm) diameter round steel
rod bent into a 2 inch radius. The female die would be half round in
cross section, and will probably be made of UHMW plastic.

What I want is for the female die to fit the male die pretty well,
allowing for the thickness of the sheet metal. I was going to make the
female die by drilling a 9/16 inch diameter hole in a rectangular piece
of plastic, and then use a saw to cut right down the centerline of the
holes, leaving a half round form. But since the male die is a bent rod,
I would then need to sand or file the the female die to fit. But how do
I know where to sand, and how much?

One approach would be to pull a piece of shop cloth (strip of sandpaper)
between the two dies, and let the shop cloth remove the high spots in
the female die. If I use that approach, I don't need to know where the
high spots are. This would not result in a perfect fit unless the shop
cloth was the same thickness as the sheet metal being formed, but it
might be good enough. Perhaps I could use two or three thicknesses of
shop cloth to approximate the 0.040 inch (1 mm) sheet metal.

But if I want to use a sander or grinder or file to get the fit right,
how can I know where to remove material from the female die?

I do not have a mill or any machine tools other than a drill press.

Thanks in advance.

Richard




--
http://www.fergusonsculpture.com
Sculptures in copper and other metals

Richard Ferguson wrote:
I think that this is a simple question, but I don't know the answer. I
am sure that a die maker would know the answer, and probably other folks
as well.

I want to make a simple male and female die for forming sheet metal. The
sheet metal is 0.040 inch (1 mm) thick.

The male die would be a piece of 1/2 inch (13 mm) diameter round steel
rod bent into a 2 inch radius. The female die would be half round in
cross section, and will probably be made of UHMW plastic.

What I want is for the female die to fit the male die pretty well,
allowing for the thickness of the sheet metal. I was going to make the
female die by drilling a 9/16 inch diameter hole in a rectangular piece
of plastic, and then use a saw to cut right down the centerline of the
holes, leaving a half round form. But since the male die is a bent rod,
I would then need to sand or file the the female die to fit. But how do
I know where to sand, and how much?

One approach would be to pull a piece of shop cloth (strip of sandpaper)
between the two dies, and let the shop cloth remove the high spots in
the female die. If I use that approach, I don't need to know where the
high spots are. This would not result in a perfect fit unless the shop
cloth was the same thickness as the sheet metal being formed, but it
might be good enough. Perhaps I could use two or three thicknesses of
shop cloth to approximate the 0.040 inch (1 mm) sheet metal.

But if I want to use a sander or grinder or file to get the fit right,
how can I know where to remove material from the female die?

I do not have a mill or any machine tools other than a drill press.

Thanks in advance.

Richard




I would think the easiest way would be to make another male component
from 14mm stock (aluminium would suffice) and use that as the reference
for making the female part. Engineer's blue on the male part would
transfer to the female hi-spots to indicate where to remove some material.

Another thought, since the female part is plastic, you could heat the
metal to the melting point of the plastic, and push it in to shape its
own recess.

--
Regards, Gary Wooding
(To reply by email, change feet to foot in my address)

The groove in the female section would be the radius of a (an
approximately) .580" rod. You could make a gauge to see how well your
sizing operation is progressing.
I wouldn't expect the .040" metal stock to form well with this type of
die set, especially not if it's steel that you want to form.

As for a technique to cut the groove, I dunno, since I don't think a
trammel/circle cutter in the drill press would work well for this job.
Maybe melt a hot .580" ring into the material, as suggested by another
reply, but that may present other problems (such as bending the rod).

WB
...............

Richard Ferguson wrote:
I think that this is a simple question, but I don't know the answer. I
am sure that a die maker would know the answer, and probably other folks
as well.

I want to make a simple male and female die for forming sheet metal.
The sheet metal is 0.040 inch (1 mm) thick.

The male die would be a piece of 1/2 inch (13 mm) diameter round steel
rod bent into a 2 inch radius. The female die would be half round in
cross section, and will probably be made of UHMW plastic.

What I want is for the female die to fit the male die pretty well,
allowing for the thickness of the sheet metal. I was going to make the
female die by drilling a 9/16 inch diameter hole in a rectangular piece
of plastic, and then use a saw to cut right down the centerline of the
holes, leaving a half round form. But since the male die is a bent rod,
I would then need to sand or file the the female die to fit. But how do
I know where to sand, and how much?

One approach would be to pull a piece of shop cloth (strip of sandpaper)
between the two dies, and let the shop cloth remove the high spots in
the female die. If I use that approach, I don't need to know where the
high spots are. This would not result in a perfect fit unless the shop
cloth was the same thickness as the sheet metal being formed, but it
might be good enough. Perhaps I could use two or three thicknesses of
shop cloth to approximate the 0.040 inch (1 mm) sheet metal.

But if I want to use a sander or grinder or file to get the fit right,
how can I know where to remove material from the female die?

I do not have a mill or any machine tools other than a drill press.

Thanks in advance.

Richard




--
http://www.fergusonsculpture.com
Sculptures in copper and other metals

"Gary Wooding" wrote in message
...

I would think the easiest way would be to make another male component from
14mm stock (aluminium would suffice) and use that as the reference for
making the female part. Engineer's blue on the male part would transfer to
the female hi-spots to indicate where to remove some material.

In most diemaking, rads on the sheetmetal part are created only with male
rads on the punch and male rads on the die. While there are instances where
one requires the female rad in the die section to form the part correctly
(coining or corner setting), in the the vast majority of cases it is merely
clearnace. Indeed, in an instance where the female rad is required, a
plastic die section would probably fail virtually instantly due to the
massive force required to coin the rad.

I would recommend building the punch as previously perscribed, but instead
of the suggested female die cavity, use only a slot (14mm+ wide) with rads
between the top surfaces and the side walls. The rads on the die section
should be as large as possibe, but I would recommend nothing less than 1mm.

Perhaps I'm misunderstaning the OP's description but this die sounds much
more like a stretch/draw die than a bending die.


Another thought, since the female part is plastic, you could heat the
metal to the melting point of the plastic, and push it in to shape its own
recess.

While a plastic die section (ideally nested into a steel yoke) would
probably make a number of good parts, the OP may want to consider making it
out of steel instead. 1mm material is not all that thin (we use 0.8mm
material to make outer body panels for cars) and he may well see rapid
wear/failure.

Regards,

Robin

Thanks to all for their thoughts.

A couple of comments: The material worked would be copper, aluminum,
and perhaps other metals, and is not likely to include steel.

I will think some more about the suggestion that I do not need a perfect
fit with the female die, that a slot is enough. On at least part of the
die, I need a good fit, since I am trying to form the sheet metal in two
directions, so I need to shrink/stretch the material rather than simply
form/bend it. But perhaps I don't need a good fit the whole length of
the die.

I am not sure about plastic dies either. I was going to prototype with a
wood upper die. Perhaps aluminum or steel would be a better choice,
although that could require getting the fit more precise.

I like the idea of putting bluing on the male die and having it transfer
to the female die. But how do I allow for the thickness of the
material? Do I need to put a part in there and blue the part?

Richard


Richard Ferguson wrote:
I think that this is a simple question, but I don't know the answer. I
am sure that a die maker would know the answer, and probably other folks
as well.

I want to make a simple male and female die for forming sheet metal. The
sheet metal is 0.040 inch (1 mm) thick.

The male die would be a piece of 1/2 inch (13 mm) diameter round steel
rod bent into a 2 inch radius. The female die would be half round in
cross section, and will probably be made of UHMW plastic.

What I want is for the female die to fit the male die pretty well,
allowing for the thickness of the sheet metal. I was going to make the
female die by drilling a 9/16 inch diameter hole in a rectangular piece
of plastic, and then use a saw to cut right down the centerline of the
holes, leaving a half round form. But since the male die is a bent rod,
I would then need to sand or file the the female die to fit. But how do
I know where to sand, and how much?

One approach would be to pull a piece of shop cloth (strip of sandpaper)
between the two dies, and let the shop cloth remove the high spots in
the female die. If I use that approach, I don't need to know where the
high spots are. This would not result in a perfect fit unless the shop
cloth was the same thickness as the sheet metal being formed, but it
might be good enough. Perhaps I could use two or three thicknesses of
shop cloth to approximate the 0.040 inch (1 mm) sheet metal.

But if I want to use a sander or grinder or file to get the fit right,
how can I know where to remove material from the female die?

I do not have a mill or any machine tools other than a drill press.

Thanks in advance.

Richard






--
http://www.fergusonsculpture.com
Sculptures in copper and other metals

Richard Ferguson wrote:

Thanks to all for their thoughts.

A couple of comments: The material worked would be copper, aluminum,
and perhaps other metals, and is not likely to include steel.

I will think some more about the suggestion that I do not need a perfect
fit with the female die, that a slot is enough. On at least part of the
die, I need a good fit, since I am trying to form the sheet metal in two
directions, so I need to shrink/stretch the material rather than simply
form/bend it. But perhaps I don't need a good fit the whole length of
the die.

Since your targets are softer metals, you might look into using a
non-conforming die. With this approach, the female "die" is simply a
flat urethane pad (in the 80 to 90 durometer range) at least twice as
thick as the desired deformation, backed by a flat steel plate. When
pressure is applied, the urethane flows around the male die, shaping
the work material as it goes. For all its simplicity, this approach
can produce amazing results in the right application. You can get
urethane pads at MSC or McMaster-Carr; they can be reused many times.
(Other types of rubber will work but not as well.)

Bert

I like the urethane suggestion a lot, not least of which because I could
use one upper die with different lower dies. The amount of skilled labor
needed on my part would also be relatively low, as well. I notice,
however, that polyurethane is relatively expensive, with a 6 inch by 1.5
inch by 1.5 inch piece costing around $25. But maybe I only need one
piece. I have a couple of questions, however.

When you say 80 durometer, do you mean Shore A, Shore D, or Shore 00?

How can I attach the urethane to a flat piece of steel, probably 1/2
inch flat bar? Can I just drill it and through bolt it? Can I use
sheet metal screws?Or is there a better solution?

I should say that I am planning to use a small power hammer in a
blacksmith style spring die to do this. Spring dies are not known for
keeping perfect alignment of top and bottom dies, but urethane solves
that problem.

Richard



Bert wrote:

Richard Ferguson wrote:


Thanks to all for their thoughts.

A couple of comments: The material worked would be copper, aluminum,
and perhaps other metals, and is not likely to include steel.

I will think some more about the suggestion that I do not need a perfect
fit with the female die, that a slot is enough. On at least part of the
die, I need a good fit, since I am trying to form the sheet metal in two
directions, so I need to shrink/stretch the material rather than simply
form/bend it. But perhaps I don't need a good fit the whole length of
the die.


Since your targets are softer metals, you might look into using a
non-conforming die. With this approach, the female "die" is simply a
flat urethane pad (in the 80 to 90 durometer range) at least twice as
thick as the desired deformation, backed by a flat steel plate. When
pressure is applied, the urethane flows around the male die, shaping
the work material as it goes. For all its simplicity, this approach
can produce amazing results in the right application. You can get
urethane pads at MSC or McMaster-Carr; they can be reused many times.
(Other types of rubber will work but not as well.)

Bert


--
http://www.fergusonsculpture.com
Sculptures in copper and other metals

"Richard Ferguson" wrote in message
...
I like the urethane suggestion a lot, not least of which because I could
use one upper die with different lower dies. The amount of skilled labor
needed on my part would also be relatively low, as well. I notice,
however, that polyurethane is relatively expensive, with a 6 inch by 1.5
inch by 1.5 inch piece costing around $25. But maybe I only need one
piece.

Unless you're making hundreds of thousands of parts, you'll only need one
piece.

There is an excellent chance the urethane will cause issues with wrinkling.
You will have no control over material flow because you do not have a
binder/pressure pad. Depending on the depth of your draw/strech, you may
even get folding. Hard dies with binders/pressure pads solve this problem,
but are not easily implimented.

You have not given us enough information about the part you're making. For
instance, what is the depth of the draw/stretch? What is the material
condition of your blank(soft/semi hard/hard), and alloy ? How many parts do
you want to make? Do you have a blank size yet, or will you cut them to
suit, as the die requires? Is the part cosmetic, or purely functional? Can
your part tolerate wrinkles?

You mentioned that you think you require a fitted die cavity to make your
part. Whether you believe me or not, I can tell you that you will _not_
require such a cavity. Where I work, we do some of the most complicated deep
drawing operations with very difficult materials, to make very large parts.
While your part *may* benifit from a perfectly spotted draw cavity, it is
unlikely that you will be willing to take the time given the benifits versus
having an empty cavity. It is also a learned skill to be able to accurately
spot a part into a die cavity.

If you insist on spotting the part into the die cavity, the sequence is
this: Spot the punch into the die first (assuming starting from scratch).
Once that's good, you'll have to open up the draw rads (between the top face
of the die section and the cavity walls) to allow for the part to flow over
the die section, and then hit a part. Apply blue to the ouside of the part
(which touches the die cavity) and hit it again. Wherever the blue has not
only transfered to the die cavity but also been hit so hard as to go white
in the middle, take that area down. At the beginning you can be very
agressive. I'd recommend a die grinder with a carbide burr, and then a pink
mounted stone. Repeat as necessary. Once you're getting many "hard spots"
all over the cavity, you have to slow down to do the final spotting. Stop
when you're only moving the hard spots around as opposed to smoothing them
out. Use a polishing stone and then fine sand paper to finish if you're
inclined.


How can I attach the urethane to a flat piece of steel, probably 1/2 inch
flat bar? Can I just drill it and through bolt it? Can I use sheet metal
screws?Or is there a better solution?

You can drill/c-bore it and use socket head cap screws. Remember that there
is virtually zero force pulling the urethane off the steel bar. Our urethane
bumpers are glued to their steel plates (not sure what kind of glue).


I should say that I am planning to use a small power hammer in a
blacksmith style spring die to do this. Spring dies are not known for
keeping perfect alignment of top and bottom dies, but urethane solves that
problem.

If you are unable to make a good part with the urethane, you should consider
hard tooling with a die set for alignment. Depending on the requirements of
the part, draw dies can be *very* intolerant of misalignment.

Regards,

Robin

Richard Ferguson wrote:

I like the urethane suggestion a lot, not least of which because I could
use one upper die with different lower dies. The amount of skilled labor
needed on my part would also be relatively low, as well. I notice,
however, that polyurethane is relatively expensive, with a 6 inch by 1.5
inch by 1.5 inch piece costing around $25. But maybe I only need one
piece. I have a couple of questions, however.

When you say 80 durometer, do you mean Shore A, Shore D, or Shore 00?

A

How can I attach the urethane to a flat piece of steel, probably 1/2
inch flat bar? Can I just drill it and through bolt it? Can I use
sheet metal screws?Or is there a better solution?

Maybe your backing plate could have channels along a couple of edges?
Or there may be some kind of adhesive that would work. I've never
tried to permanently attach urethane to anything. Before drilling or
sawing, be sure to read the MSDS. If I recall correctly, toxic fumes
can be released in some machining operations.

I should say that I am planning to use a small power hammer in a
blacksmith style spring die to do this. Spring dies are not known for
keeping perfect alignment of top and bottom dies, but urethane solves
that problem.

If the size of the part allows it, you might be better off building a
shallow box into which you could stack the male die, work piece,
urethane pad, and backing plate.

I've only used the urethane pads in a hydraulic press, so I can't say
if they'll work with a power hammer. I've never heard of them being
used like this, and I suspect the results will not be great, but I
don't know. Depending on the size of the part, the size of the hammer,
and the amount of deformation, you may not be able to generate enough
force, and even if you do, you may not have enough control over the
amount of force applied. Depending on the shape and how much
deformation is involved, you may need to do the forming in multiple
steps, annealing the part between steps, to avoid tearing.

Richard



Bert wrote:

Richard Ferguson wrote:


Thanks to all for their thoughts.

A couple of comments: The material worked would be copper, aluminum,
and perhaps other metals, and is not likely to include steel.

I will think some more about the suggestion that I do not need a perfect
fit with the female die, that a slot is enough. On at least part of the
die, I need a good fit, since I am trying to form the sheet metal in two
directions, so I need to shrink/stretch the material rather than simply
form/bend it. But perhaps I don't need a good fit the whole length of
the die.


Since your targets are softer metals, you might look into using a
non-conforming die. With this approach, the female "die" is simply a
flat urethane pad (in the 80 to 90 durometer range) at least twice as
thick as the desired deformation, backed by a flat steel plate. When
pressure is applied, the urethane flows around the male die, shaping
the work material as it goes. For all its simplicity, this approach
can produce amazing results in the right application. You can get
urethane pads at MSC or McMaster-Carr; they can be reused many times.
(Other types of rubber will work but not as well.)

Bert