What press force is needed ?
Andre Majorel
needed for a given job ? Specifically, punching holes about
1 cm� in 1 mm steel or 3 mm aluminium.
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Andr� Majorel <URL:http://www.teaser.fr/~amajorel/>
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Mark Rand
<che...@halliburton.com> wrote:
>Thanks for the hint, Ned. How do you know what press force is
>needed for a given job ? Specifically, punching holes about
>1 cm� in 1 mm steel or 3 mm aluminium.
Go to a site such as http://www.matweb.com/, look up the shear strength of
your material of choice noting the units psi..N/m^2 etc and converting if
required.
The force you need will be the area you're cutting through multiplied by the
shear strength, plus a bit for luck.
HTH
Mark Rand
RTFM
Buerste
"Andre Majorel" <che...@halliburton.com> wrote in message
news:slrnhmq106...@atc5.vermine.org...
You can reduce the amount of force by grinding an angle on the punch.
Joseph Gwinn
Mark Rand <ra...@internettie.co.uk> wrote:
Area, or is it perimeter?
Joe Gwinn
Wes
>> The force you need will be the area you're cutting through multiplied by the
>> shear strength, plus a bit for luck.
>
>Area, or is it perimeter?
Area I think. Which would be permimeter x material depth x shear
Wes
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Joseph Gwinn
Wes <clu...@lycos.com> wrote:
> Joseph Gwinn <joeg...@comcast.net> wrote:
>
> >> The force you need will be the area you're cutting through multiplied by
> >> the
> >> shear strength, plus a bit for luck.
> >
> >Area, or is it perimeter?
>
> Area I think. Which would be permimeter x material depth x shear
Area of the sheared material, but not of the piece being punched out.
That's the distinction I was making.
Joe Gwinn
Ned Simmons
<che...@halliburton.com> wrote:
>Thanks for the hint, Ned. How do you know what press force is
>needed for a given job ? Specifically, punching holes about
>1 cm� in 1 mm steel or 3 mm aluminium.
Force = sheared area x shear strength of the material x punch
geometry fudge factor
http://www.precisionsheetmetal.com/home/forces.htm
--
Ned Simmons
Mark Rand
Yes, I guess I skipped that part of the explanation. My bad.
Mark Rand
RTFM
DoN. Nichols
> Thanks for the hint, Ned. How do you know what press force is
> needed for a given job ? Specifically, punching holes about
> 1 cm� in 1 mm steel or 3 mm aluminium.
The formulas are in _Machinery's Handbook_, including
coefficients for steel and (I think) aluminum.
But basically, it is based on the total length of the cut
(circumference of a circle, or 4 x the length of the side for a square.)
Thickness comes into the equation as well, of course.
What is the symbol after "1 cm" in your quoted text above. It
appears to be an extended ASCII character which displays differently on
different systems, and with different character sets loaded. On my
system, it shows as "\262", which is a value which won't display on my
system. Is it perhaps a superscript '2' to indicate a square cm? Is
so, the cut length will be 4 cm.
You do have a _Machinery's Handbook_ don't you? if not, you
should.
Good Luck,
DoN.
--
Email: <dnic...@d-and-d.com> | Voice (all times): (703) 938-4564
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John
> Thanks for the hint, Ned. How do you know what press force is
> needed for a given job ? Specifically, punching holes about
> 1 cm� in 1 mm steel or 3 mm aluminium.
>
Y^u multiply the length of the shear line by the thickness of the metal
being punched. That will give you an area .. length x height.
You then look up the shear modulus of the metal you are punching which
is usually given in units of force per area.
multiply you area by the shear modulus and that number is the ideal
force you will need.
other factors are how sharp is your punch. Temper of the metal. How
well your punch clearances are. How your punch is tapered so it does not
hit the whole shear line at once.
That will give you a starting point. You probably should allow about 20
percent more force than the formulas come up with until you run some
jobs and see how the press handles them. If you are using an older back
geared press in good shape the tonnage is almost always underrated. An
older 90 ton Bliss looks beefier than a newer 150 ton.
Have fun and watch your fingers.
John