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Thread: hexagonal hole

  1. #1
    ninthst is offline Aluminum
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    Other than using a drill and a file how do I make a hexagonal hole [ 3/4 across the flats ] in 1/4 inch aliminum plate/ I have the usual mill, lathe, drill press, etc.

  2. #2
    Jeff is offline Hot Rolled
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    There are hex broaches available if you can justify the cost. Probably the easiest way for one aprt would be to mount the part on a rotary table, drill out the center, then mill the flats (using the r/t to index the part)using a 1/8" or smaller end mill...there will be very little left in the corners to file. You could make a sort of broach to do one flat at a time (out of an end mill), then lock the spindle somehow and up/down using the quill handle to "broach one flat...index using r/t to do next flat, etc...

  3. #3
    JimGlass is offline Stainless
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    I'll assume you need only one hole.

    Easy way might be to mill it out with a 1/8" or 3/16" endmill. 1/4" thick aluminum should be no big deal. If you had an indexing table that would work great. If not, scribe out where the hex goes and move the work piece with a protractor then mill to the scribed line. You will only need to move the piece 2 more times. If the fillets at the corners (left by the endmill) of the hex are objectionable file them out.
    I think the hex on a 1/2" bolt is a 3/4" hex.
    Use the bolt as a gage to check yourself. Use plenty of RPM when milling aluminum and use pipe threading oil or motor oil to flush away the chips.

    Take your time and use a magnafine glass as you mill to the lines. You may amaze yourself at what you can do.
    Jim

    [This message has been edited by JimGlass (edited 11-02-2003).]

    [This message has been edited by JimGlass (edited 11-02-2003).]

  4. #4
    winchman is offline Stainless
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    There was a similar question posed a while back. I think the best answer back then was to drill a small hole (1/16") at each apex, remove the bulk of the material with drills, then finish up with a small diameter end mill.

    Roger

  5. #5
    gerdb21@hotmali.com Guest

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    I would use a broach unless it is really ONLY one hole and never another hole again

    its easier to work on dimensional quality on an outside broach diameter then to create it in an inside hole diameter with multiple passes of an end mill

    once you have the tools and proceedure, its a piece of cake to repeat it, while using an endmill you likely will screw it up eventually

    making your own broach isn't that difficult if you put your mind to it, i had to do it once and i was surprised how easy it was and it worked well, too


  6. #6
    Rich Carlstedt is offline Stainless
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    1/4 " plate isn't too thick, so you could try taking a 1/2 inch nut(3/4 hex) and putting it in the lathe and hit it with a countersink till it has sharp edges, then make a steel bushing with a ID to go over the corners(diagonally.
    Drill a 1/2 inch hole in the Aluminum, put a very heavy washer and bolt thru the bushing and into the hole and bring the nut up tight on the back side and "Torque her through"
    I might extrude some of the Aluminum, but you will your hole without expensive tooling

  7. #7
    Dr. Rob is offline Hot Rolled
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    Hey, whoa...A hex broach? Hardened? Use an Allen key. Dirt cheap, plenty long, any size.

    Rich is onto something up there.

  8. #8
    Sean S's Avatar
    Sean S is offline Titanium
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    Nuts and Allen wrenches for broaches... quite interesting!

  9. #9
    sbwest Guest

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    I have used an allen hex to broach a steel part using a bench vice to force it thru. Works great.
    Walt

  10. #10
    Dr. Rob is offline Hot Rolled
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    Sure, no prob. I use a corresponding hex from socket set with the allen wrench for punching.

  11. #11
    J Tiers Guest

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    3/4 inch seems large for use of an allen key.

    I assume you do not have access to a shaper (or slotter)? That would let you finish a drilled hole out to size in short order with sharp corners.

    But for aluminum, you can mark it out, and file to the line after either milling or drilling out the bulk of the material.

  12. #12
    JRIowa's Avatar
    JRIowa is offline Diamond
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    Used to do stuff like that all the time until wire EDM came along. I still have some of the tools in my box. HSS brazed on a dowel pin. Usually have a 45 deg. point on them and put in collet. Lined up with one side of the hole and used quill handle to move up and down. Work just like a shaper, but you can only take a couple of thou. per cut.

    JR

  13. #13
    Cass Guest

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    Making a broach from an Allen wrench is not as easy as it sounds especially in a large size like 3/4". I have done it for 1/8" hexagonal holes and 1/4" for square holes and ground relief for the cutting edges and it still doesn't work very well compared to a real broach. A 3/4" push broach will cost a lot of money unless you are doing a lot of holes. For one hole in 1/4" aluminum I would use the idea of drilling small holes in the corners and then a big hole to knock out the bulk of the material. You can then finish the job with a small end mill or with a scroll saw or even a hand held jig saw and a file. I would use a No. 50 drill if you want sharper corners in the hex. You can make that hole faster than you can read all this advice. Making and using a broach is an all day job if it works at all.

  14. #14
    Richard Rogers is offline Titanium
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    Convenient: Punch it, or get it punched if possible.

    OR

    Exotic: Watts Brothers Tool makes a method of drilling that type of hole. I had one of their setups once, but sold it. IF you know someone with that setup, maybe you could con them into doing it.......

    good luck

    Richard

  15. #15
    JRIowa's Avatar
    JRIowa is offline Diamond
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    Here's what we use. It's pricey for one, but aside from the noise, sure works neat!

    http://www.slatertools.com/rotary_broaching_cat.htm

    JR

  16. #16
    Arno's Avatar
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    JR,- that's often called a Wobble Broach. Although typically used on automatic screw machines, it can even be used in a drill press.
    Arno

  17. #17
    ninthst is offline Aluminum
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    Thanks to all for your suggestions. I think I will try the approach of drilling a small hole in each corner and drilling, milling out the remainder.

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