Shop Press As Clicker Tons Needed Question

[Kendog]

Hi everyone,

So I've been looking into modifying a simple shop press to use as a clicker and it seems that 12 tons gets the job done.

But I'm wondering if I can get by with something in the 1 ton range for thin leather around 3 to 4 or even 5 to 6 ounce for pieces the size of a small key fob.

Thanks,

KD

[JLSleather]

Short answer -- yes. Those people telling stories about 12 and 20-ton presses perhaps are not understanding the meaning of TONS

Officially, the pressure required to BLANK a die-cut part is calculated .. length of the cut times the shear strength of the material times the thickness of the material.

So, cut a 9" x 4" rectangle. Perimeter (cut length) is 26". Thickness of say 6 oz (.093). S=~2000lb

That's pounds, so divide by 2000 to get tons.

Then (26 x .093 x 2000)/2000 = 4.8 tons FOR BLANKING

But, you're not blanking - you're cutting. So "guestimate" roughly 1/3 the pressure. In the case of your "fob", your perimeter is more like 10", so you'd need like 40% of the pressure ...

[stelmackr]

I use a book press to do all my clicking and embossing. If you google "book press for sale" and look at the images, you will see what I'm talking about. I remember calculating the force that my book press exerts. It was number of threads per inch, the length of the handle, and the force of the operator. I think I came up with 7-tonnes. The one I have is so nice looking that my wife lets me keep it in the house as part of our furniture decorations.

For embossing I place my cased leather on a piece of matte board on top of a hardboard.

For clicking I use a cutting board from Harbor Freight.

In either case, positioning the leather is critical to a good embossing or clicking. I usually wind up pressing several times, moving the object fore and aft--left and right.

Bob Stelmack

[stelmackr]

Oh ya, and I bind books with it ;-)

[DavidL]

Short answer -- yes. Those people telling stories about 12 and 20-ton presses perhaps are not understanding the meaning of TONS

But, you're not blanking - you're cutting. So "guestimate" roughly 1/3 the pressure. In the case of your "fob", your perimeter is more like 10", so you'd need like 40% of the pressure ...

Do all veg tan and chrome tan have roughly a shear strength of 40 percent of blanking (800lbs). What is blanking Im not familiar with this term.

When I did the math I got 2.4 tons or 4800 lbs. Is this the how to calculate it or did I do something wrong while calculating?

26 inches * .093 inches * 2000/2000 = 2.4 Tons = 4800 lbs.

[JLSleather]

OOPS Yep, 2.4T. Musta fat-fingered the '2' twice? I THOUT that sounded awfully high! Blanking is like cutting out. Generally involves a male and a female die, with some calculated clearance. Substance being "cut" actually fractures, not really "cutting". Think tin can lids being stamped out of sheet metal...

The 40% I was talking about was the length of the cut (10" is a guess at his "fob" and safely no more than about 40% of 26", depending on actual meas.). "Shear" is just used to describe stuff being cut at right angle to it's surface. If it was being pulled from the ends, that's tensile strength (yes, I know that's over simplified). To illustrate how much change is involved, take a pair of shears you know to be sharp. Open it, press the blade down on a piece of paper. Now, try cutting as with shears normally. Much ess pressure needed, due to "shearing" action.

Actually, this "shearing" action is often used to reduce the pressure when 'blanking', but that's another can o worms...

And no, not all leathers have the same shear strength. Some leathers are more dense than others , or more hard than others, or tanned differently than others... but I'm figuring his question was what is "enough".

I have a 20-ton press, only because it was the same price as a 10 and a 12 at harbor frieght when they had a local sale, so I had one picked up.

Edited April 22, 2015 by JLSleather

[Kendog]

edit: ok I will have to re figure the #s a bit and possibly need to clarify cutting vs shearing

This is great info.

The fobs I have to cut out are only 5" perimeter so a half ton press should get through 6oz, barely, but should be no problem for 3 oz. One ton should get me in the game with no worries. Now I just have decide if I want to get fancy with a book press and click in the comfort of my own home

Thanks --

KD

Edited April 22, 2015 by Kendog

[pg043]

I think usually the reason people use the 12 or 20 ton presses is just to accommodate larger dies, as the smaller shop presses usually have a fairly small work area. Key fobs obviously won't require too much workspace :D

Edited April 24, 2015 by pg043