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Here's a excel spreadsheet that will do all the number crunchin' for you. Enter values in yellow hi-lited cells only.
I combined a couple different ones I have made for solving failures and making life easier, T=KDP & Rotational Torque calcs. I converted the whole kit & kaboodle back to .xls from .xlsx....as I didn't save the originals....
I gave 'er a test....seems to be OK....lemmeeno if you have a problem. Sometimes regressive conversions turn up a glitch.
I tend to look at this like Neander. We don't know the press screw width and it would be coarser if Acme or Square thread. When I look at Pexto or Roper Whitney? Those type which are a super heavy "C" clamp type, you clamp in a vise and with a handle of 18-24", can get travel of about 1/8" in 180* swing (ifIRC). The pressure is on the sides of well lubed, square threads like a larger press.
In light of more recent post, it may be a new design is wanted and this is good info.
Don't need fancy math or spread sheets ( although I use them)
Lets walk through it for you and others,
Shear is ALWAYS 75 % of the tensile strength (Called "T") of the steel
So if you use normal steel with 60,000 PSI ( T ), then you have 45,000 T during shear
So a 1 inch square bar would require 45,000 pounds to shear off.
Since your material is only 1/8 inch thick, it would require 45,000/8= 5,600 Pounds to shear off a piece 1 inch wide
If your punch has 3 sides , .25, .25, ,353 then the total length is .853 OR 85 % of 5,600 lbs which equals 4,800 ~ pounds
Please know this . The force required is based on a close fit between the punch and die ...like .002" clearance max
As the clearance goes up the tonnage increases ! Sort of like scissors when they cut paper and they are loose fit, takes alot !
Shear calculations are based on no clearance
so you need about 3 Tons ( 5,600 # )of force
Now look at the screw you will use if not hydraulic jack.
Take the pitch of the thread and the diameter of the screw
The pitch of 8 TPI for instance is .125 .
Take the diameter of the thread ( say 1 inch) and multiply that by Pi ( 3.14), so 1x 3.14= 3.14 ( Circumference )
Divide the pitch into this (Pi x D) number to get your thread leverage ( 3.14/.125= 25~)
So if you divide the force needed of 5,600 pounds by the leverage ratio of 25 you get
(5,600/25 = 224) 224 pounds of force required for the perforate the work
Put a 2 foot lever on the screw and apply 112 pounds and you have it
Rich
This is a over-simplification of the problem but will yield good results for home shop work
If you wanted to punch a 1 " round ( 1 x 3.14=3.14) through the same material it would take about 70 tons of force ( 45 K x 3.14) , and if the punch had a radius, then much more , but that is beyond these words
Great info which buffers other info. It is important to note that the dies of these things have normal Vee threads. They have a lot of them and while hollow, cannot expand because they are captive in the heavy fixture. That is different than using a Vee thread to drive the punch.
Nitrous:
I surely hope this is an academic exercise and you are not just planning to conjure up all the hardware for one triangular hole, because it would be far easier to drill and file this feature once. Or if you need many of these I would suggest that you talk to a wire edm vendor.
Incidentally, if you decide to punch this hole, you had better plan on a massive system including a means of holding the piece of 1018 in place while punching. This amount of shear force will cause all kinds of distortion of the remaining part if it is not held in place by a heavily loaded stripper plate, and the remaining part must be large enough for the stripper plate to grip it. Die clearance should be about 20% of the material thickness for mild steel, so for 1/8" material the clearance between the punch and die should be 0.025". The ideal situation would be to have the punch face tapered from each of the points to the center of the triangle. The taper needs to be about 30% of the material thickness. This would allow a gradual shearing effect instead of a one and done rupture. The points will not hold up very long if they are the first to contact. Heat treating the sharp cornered die will be problematic, too, as it will be prone to cracking in the corners.
Most screw presses, as was noted, are either Acme, Buttress or sometimes Square threads. This is because the thread shear area is greater, and less prone to jamming than 'v' threads are. By this I mean, the non-'v' thread forms are better for transmitting loads again and again as opposed to a fastener that generally gets torqued a few times in its life and is expected to stay in place.
The other gentlemen's engineering calculations are right on.
--earlgo
Before you do anything, you must do something else first. - Washington's principle.
