making a square hole in round bar?
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  1. #1
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    Default making a square hole in round bar?

    I was wondering what is the best way to have a 30mm square hole cut out of a piece of 3" round bar that is 4" long. I was thinking the easiest way is to have someone with a wire edm cut it out.

    I am making a lower tool holder my Trumpf nibbler that im using for doing some car panel shaping with. The top holder uses 30mm square bar but the lower is set up for a round tool holder. I figured if i make a new lower that uses the same size tool holder as the upper, it would be a lot easier to make tooling and line things up.

    Ill add a picture of the current lower tool holder, some tooing and that should give and idea of what Im looking to do. If there is any better ideas than cutting it with and EDM let me know. The rest of the machining is east to do, it just the square hole i cant make. Ill have to send it out some place since there is no one around here that does that kind of work so if there is some good places of if anyone on the form does that, please let me know.

    thanks
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    d1e378e1-a111-4505-8c5b-85ed96fc4e23.jpg
    e3e597f3-b602-422d-a341-f575f43f1a52.jpg

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    I think that is too deep for rotary broaching. Does the square go all the way through? so a shaper could do it?
    Bill D

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    Depends on how sharp the corners need to be. Drilling progressively larger holes to relieve the corners then milling out the bulk could get you pretty close.

    Or relieve the corners entirely. Or drill a big hole and fix some pads in it.

    Lotta ways to skin this cat that don't involved a wire machine.
    Sent via CNC 88HS

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    Wire is the best way, but it is slow and expensive. Can you make it in two pieces and then weld it together? Leave the OD oversize for a final turn op after welding.

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    Quote Originally Posted by Bill D View Post
    I think that is too deep for rotary broaching. Does the square go all the way through? so a shaper could do it?
    Bill D
    ya the hole goes all the way through. never though about a shaper, that is something i might be able to find around here.

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    Quote Originally Posted by Kyle Smith View Post
    Wire is the best way, but it is slow and expensive. Can you make it in two pieces and then weld it together? Leave the OD oversize for a final turn op after welding.
    I though about making it in 2 pieces and welding them back together, i was just trying to save some time. I was also looking at trying to find a square broach but didnt find anything.

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    I think ill just put it in the lathe and drill out the bulk of the material i need to remove, once that is done i will split the round bar in half and mill the slot out so i have square corners then weld it back together.

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    I have made square holes, and splined holes, simply by drilling out the center, drilling small holes at the four corners, and filing the material. Takes a while, but the old armstrong method works just fine.

    German apprentices used to have to file a perfect cube, then, when it passed, file it into a perfect sphere.
    Filing isnt particularly hard, and its pretty hard to ruin it by going to far...

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    You can by sleeves with square holes. These are inch:

    Green Bay Manufacturing

    Perhaps metric is available as custom or elsewhere?

    Bill

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    I would drill four small holes in each corner then one big one centered on the desired square. Then use a keyway broach four times.
    Bill D

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    I was going to suggest that. I have a chuck wrench with a square hole. It was made by milling a slot from the side of the round stock and then a (rectangular?) piece was brazed into it to form the fourth side. In my case the end of that rectangular plug was rounded to the radius of the milling cutter, but you would not need that if the hole goes all the way through. The OD was probably finished after that. You have to look close to see the joint. If you have enough meat between the square hole and the OD, it will be almost as strong as the original steel.

    Brazing would produce less distortion than welding and with full penetration of the braze into the crack, it will probably be as strong or stronger than a weld unless a lot of care is taken.



    Quote Originally Posted by climb-101 View Post
    I though about making it in 2 pieces and welding them back together, i was just trying to save some time. I was also looking at trying to find a square broach but didnt find anything.

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    Got files?

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    Cut bar in half, mill slot in both halves (longitudinal cut in half!) bolt back together or weld or whatever, I’m sure I’ve bought off the shelf bolster blanks years ago, I think they were flame cut or water jetted
    Mark

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    I dunno about you guys ... if this isn't a perfect excuse to buy a 6" Pratt & Whitney slotter, I'll be a blue-nosed gopher.

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    Quote Originally Posted by Cole2534 View Post
    Depends on how sharp the corners need to be. Drilling progressively larger holes to relieve the corners then milling out the bulk could get you pretty close.

    Or relieve the corners entirely. Or drill a big hole and fix some pads in it.

    Lotta ways to skin this cat that don't involved a wire machine.
    Sent via CNC 88HS
    yep this is the best way, mickey mouse ear the corners. not like they do much anyways unless its a die for stamping.

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    Believe Kyle has got it right

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    Default Make a broch

    Quote Originally Posted by Bill D View Post
    I would drill four small holes in each corner then one big one centered on the desired square. Then use a keyway broach four times.
    Bill D
    In addition "Bore" a hole the size of the square broach. Make your O1 60-62Rc square broach with a round pilot the size of the hole on the front of the broach. Undercut the pilot to allow clearance for the chips from broaching. Make your work pieces in one inch thick sections. Then screw and dowel together after broaching the four sections using the broach to align the sections. Use oil. Broach the openings in a press a very short distance at a time, remove the broach and file to clean out the scrap. Then repeat until finished. If greater accuracy is required make two broaches. One .002 undersize. One on size. Takes a little time but you can do this in your own shop.
    The broach is nothing more than a square with a pilot on the end.

    All The Best
    Roger

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    Easy to do on a slotter...Phil

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