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darryl
07-03-2007, 03:05 AM
I'm about to build an accessory to enable me to punch holes, nibble edges away, etc. I have a 4 inch square column which has a drill press head mounted on one end, and two adjustable tables mounted on it. When not used as a horizontal boring machine, it hinges upright to take up less space. In the vertical mode, I can see attaching a sort of small table to it where the dies would go, and an upper mechanism which would have a lever handle to operate the punch. It won't be a problem to orient things so the punch will center in the die as it's coming down- that's just part of designing it properly and building it solidly. All this additional stuff would hang downwards when the horizontal boring configuration is being used, and so it won't interfere with that. As a punching machine, I think it'll find the most use for chunking out material up to a drawn line, where currently a file is the way I usually have to do it. The cutting tool in this case is probably going to be a 1/4 inch square hss bit that's inserted into a larger piece of metal that would fit into the punch holder. The material being punched would be mostly sheet aluminum from say .030 thick to about 1/4 inch, and some stainless up to about 1/16 thick. For the thicker aluminum, I would be more or less shaving chips away to approach the dimension. I don't expect to be able to punch out a hole in one go with the thicker stuff. A question- what might be a cost effective, but decent set of punches and dies that I could design around? If I made my own, what material would be best both in terms of proper functionality and relative ease of hardening in the home shop?

Another thing- since I'd like to be able to make large holes in thicker stuff, I'd be drilling holes all around, knocking out the center, then dealing with the rough edge left behind. This is where the shaving would normally come in. I guess to look at it another way, it would be shaping. Anyway, it would be nice to be able to select an arc shaped punch to do this type of job more cleanly. Is this something that's available, and does this need a matching die in order to work properly? If I used the edge of a round punch for this, it would be putting a considerable side force against it, which would mis-align it with it's die. I do wish to avoid problems where I can.

Scishopguy
07-03-2007, 01:37 PM
Heinrich makes a lever acuated punch unit with interchangeable dies and punches for metal up to about 1/8" thick. It is similar to the Whitney Roper #2 junior, except much larger and the dies are square. They are held on a flat surface and adjusted side to side and front to back by set screws on all sides. You have to set the clearances when you change the dies but they work well and last a long time. The one we had at the university shop I worked in was purchased from MSC and cost about $150 back in 1985. It came with a full set of round punches and dies up to about 5/8" and two different sizes of square punches and dies. You could get other shapes and sizes from them as needed. Good machine.

darryl
07-04-2007, 01:52 AM
Well, that's interesting since my name is Heinrich. I'll have to search Heinrich Co for more info. Thanks.

Depth of throat is interesting since that determines how much bending moment the column I have will take. On one hand, I can design for a certain depth, say 8 inches, then accept the degree of power I can get without overstressing things, or I could design for a certain maximum pressure and then cut back on depth of throat until the parts are able to withstand it.

Because thicker material allows better for drilled holes, I'll design for an 8 inch depth, and restrict punching to the thinner materials. I'll still be able to shave chips off thicker material if I'm not taking too much of a bite at once. Some simple math says I should be able to get a stroke of about 5/8 inch with about 3000 lbs of force with a lever about 3 ft long. I could incorporate a hydraulic jack in the mechanism, but it would probably be cumbersome to operate. I want to keep this simple, so I'll probably make one punch and die to start with, and leave room to accommodate a commercial set in the future. The one I make will be able to punch slots or shave from one edge. That will take care of most of what I'll be using it for. Pictures in a few weeks, as play time permits.

Ries
07-04-2007, 11:31 AM
A ton and a half is tiny, for a punch.
check out this chart from Roper Whitney- you can see that a ton and a half will do about a quarter inch hole in 16 ga.

http://roperwhitney.com/tech/chart1.cfm

I have a 24" throat hand operated punch, an old W.A. Whitney, and it is rated at ten tons- its a bigger, older version of this one-
http://www.americanwhitney.com/92BenchPress.asp
And everything about it is incredibly big and strong.
The punch body is 4" thick solid plate, cut in a c shape, and weighs something like 500lbs.

I would imagine that using a 4" round or square tube, and an 8" throat, you will be restricted to pretty small holes, especially in steel. The forces involved will want to flex that post, and all your connections.

Still, it should work.
Nibbling is usually done with round punches, not some funny shape. They just use big, rigid frames to hold the punches in alignment.
A pullmax, for example, was often configured as a nibbler, running 1/4" round punches- but the frames weigh in the vicinity of 5000 lbs, and this helps keep the punch and die aligned.

american whitney, or roper whitney, would be good places to get punches, or at least brands of punches to use, and buy on ebay,because they are industry standard, and available in so many shapes and sizes.

http://roperwhitney.com/index.cfm