Hi, I need to cut about two-dozen square 5/8" holes in cold rolled .187" thick steel bar. I'm thinking that broaching would work, but was surprised that a 5/8" broach would set me back $300. The holes need to be square and fairly precise. The .187" CR steel is too thick for my whitney foot punch to get through, so I'm kind of at loose ends.
Have I overlooked some other alternatives? Is there a source for cheap square broaches anyone knows about?
You could use a Watts polygonal drill, but it's probably just as expensive as a broach. With the foot punch, have you tried drilling out most of the material and punching out the rest? When I did some work with a Pexto rotary punch (hand powered), I found that with the largest punches, I needed to drill out as much as possible, but then I could punch the rest.
If you can live with a 1/16" radius in the corners you could mill the opening with a 1/8" dia. endmill. Set stops at appropriate locations for the X and Y axes, drill a 19/32" dia. hole in the centre of the required opening, switch to endmill, and crank axes to stops. Voila!
You can buy square hole sleeves and silver solder or weld them in, but at $10-$15 per sleeve, you are competetive with buying a broach. Ugh!
How close to the edge are you? Part size? Holes cannot be round? Milled out with drilled out clearances in the corners? Wire EDM shop ($$$)
Got a fab shop near you. They would likely have a set of dies for an ironworker. No Idea what it would cost. Anywhere from a box of donuts, a case of beer, or all the way up to the cost of a broach, but I doubt that it would cost that.
Similar to the drill-and-punch idea, has anyone 'spot-faced' 90% of the way through with a mill (diameter equal to the square hole size), then punched?
Thanks to All for those answers, I don't think building an EDM machine is in the cards for me. I guess I'll just have to pony up for the broach.
I don't have an H-frame press (but I suppose this is as good a time as any to get one if I have to). Is it ill advised to try to hammer a broach that size? if hammering it works I'll just do that. Any opinions on who makes the better broach?
-Don't hammer the broach - it's brittle and slender. The teeth will chip, and it's not difficult to snap a long broach in half. In production, long broaches are pulled.
-An arbor press is a much better rig than a hydraulic press for broaching in most cases. A Dumont 5/8 square broach is about 16" long; that's a lot of pumping on a manual hydraulic press. The arbor press also gives a better feel, making it less likely the broach will get broken. But it'll take a good size arbor press to handle a 16" long broach.
-Back off the press ram frequently and allow the broach to relax. If the press ram and the broach aren't perfectly parallel, the broach may bend enough to snap if you don't allow it to spring back into line.
-Normal square broaches have a round pilot. The pilot diameter is slightly larger than the distance across the flats, so while the corners of the hole are sharp, the sides bulge a bit.
There's having it plasma or laser cut - call around to local shops.
Filing could be an option, but depends on the value of fairly precise, and how hard you want to work.
One thing I'm seeing when I look at a 5/8" broach in a catalog (Enco, $249) is that the tooth spacing is 7/16" and the minimum length of cut is 5/8" - so you may need to clamp several of your bars together for a broach to even work properly, unless there are broaches of this size with finer teeth than the Dumont I'm looking at.
You don't say how precise. If a couple of thou would do, there's this thing called a three-square file. Use a drill for the bulk, files for the corners and a shop made go/no-go gauge to tell you when to stop.
At $300, you might be best off just going to a local shop that has a Scotchman-style single station hydrolic punch and see what they'd charge you. Doesn't take long to set something like that up and run, and you might get it done for $50 or less.
That's a possibility, but you're better off if you can get them punched- at least at my shop, laser cutting is $100/hr, but punching is only $60.
Come to think of it, how many parts do you need? Is it a matter of having two dozen holes in one part, or two dozen parts with one square hole each? If it's the former, I could do that for you pretty cheap, provided 1008 CRS would be acceptable. Two dozen parts would cost more, obviously.
I have an electric file die grinding double table that works just fine for sell... It works like a jig saw with a file in it... Very heavy duty... It's about the size of an office chair and weights around 250 lbs.
110 volts works great... Upper and lower table... First $150.00 takes it... E-mail at ( kbeitz @ pa.net ) located in Pennsylvania....
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