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  • How do I make a square hole

    Spin Doctor.

    Watts Drill.

    franco

  • #2
    How do I make a square hole

    I need to make a new knob for an old altimeter (1920s vintage) but I don’t know how to make a square hole.

    The altimeter has a 1/8th inch square post (coming out of the case) that is taped for a small screw to hold the knob on. I can make the round knob but I don’t know how to cut a square hole into the knob about 1/8th inch deep. I’m assuming I should be working in brass as the post is brass (I think). All I have is a lathe (1940’s vintage) and a small drill press. Any suggestions?

    Thanks

    Chris

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    • #3
      A few ideas. One, you might try to "borrow" a square hole of the right size, from some other part, that you could insert into a larger drilled hole in the knob. You may be able to buy a "square hole sleeve" of the correct size. Check www.reidtool.com to see if they have any. I know they have square hole sleeves, but I'm not sure they go down to 1/8".

      As far as actually making a square hole. If it's a through hole, you could try filing out the corners of a round hole with appropriate needle files.

      Or, make a square hole broach out of drill rod. Machine (or file) a 1/8" square on the end of a piece of maybe 3/16" drill rod, with the square section being maybe 1/4" long. Put it in the lathe and countersink the end just a bit so it forms sort-of cutting edges on th end. Heat up with a torch and quench to harden, then align with a pre-drilled 1/8" dia. hole in the knob and press in with your drill press quill to plane out the corners.

      Getting the broach aligned with the hole may be a little tricky on a drill press. Unless it's aligned really well it will want to go off to one side or the other.
      ----------
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      • #4
        Drill a 1/8" dia hole deeper than you need the square hole. (For chip clearance) Then press a piece of 1/8 square keyway stock into the hole to broach the hole square. (Beleive it or not there are special drills that drill square holes but I do not know if they come that small and it would not be worthwile to buy one for one hole.) Gary P. Hansen
        In memory of Marine Engineer Paul Miller who gave his life for his country 7-19-2010 Helmand Province, Afghanistan. Freedom is not free, it is paid for with blood.

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        • #5
          Don't rule out 5 minute epoxy. Many a $1000 custom knife is held together using this stuff. You can mix some lamp black with it for a black color. It has the benefit of not getting brittle.

          another option. hammer form a piece of round brass tubing onto a square mandrel. Then, drill a hole in your know, insert the squre tube and solder in place. Should hold till hell won't have it.

          edited to add:

          if you need to remove it just heat knob lightly with propane torch and the epoxy releases it's grip.

          [This message has been edited by Your Old Dog (edited 03-03-2006).]
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          Thank you to our families of soldiers, many of whom have given so much more then the rest of us for the Freedom we enjoy.

          It is true, there is nothing free about freedom, don't be so quick to give it away.

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          • #6
            Another possibility is to drill a hole that just clears the square and use a set screw to retain the knob on one of the flats of the shaft.

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            • #7
              Okay, a 1/8-inch square hole 1/8-inch deep, right? This is how I would do it with the tools you have. Actually all you need is the lathe.

              Chuck up a brass knob blank in your lathe and drill it all the way thru with a 1/8- inch drill bit. Then turn the material around in the chuck and drill or bore another hole about .250 (or whatever) to within 1/8-inch of coming thru. File, or broach, the remaining material square. Then make a brass plug for a press fit into the .250 hole. Machine outside to desired shape.

              ________________________


              [This message has been edited by Mike Burdick (edited 03-03-2006).]

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              • #8
                All excellent ideas. I recall seeing some small brass square tubing at the Hobby store may try that and some epoxy in a round hole. I think I will try all of the suggestions just to see how well they work.

                Thanks again
                Chris

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                • #9
                  I had to make a winding key for a table clock years ago. It needed a square hole about that size. Keep in mind the hole doesn't have to be entirely square, just enough corners to make it hold. I drilled a hole a bit under the diagonal dimension and ground the shank of an appropriate drill bit square. Tapped it in and voila, square cornered hole.

                  Oh yeah, the drill is a bit difficult to get back out but I will leave that as an exercise for the readers.

                  [This message has been edited by Evan (edited 03-03-2006).]
                  Free software for calculating bolt circles and similar: Click Here

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                  • #10
                    Use a square drill. Yes, they do make such things. They consist of a hollow square-cornered broach with a drill running through the center.

                    Illustration and discussion on Wikipedia http://en.wikipedia.org/wiki/Mortiser

                    ------------------
                    Leigh W3NLB

                    [This message has been edited by Leigh (edited 03-03-2006).]
                    Leigh
                    The entire content of this post is copyright by, and is the sole property of, the author. No assignment
                    of title nor right of publication shall ensue from presentation of this material on any computer site.

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                    • #11
                      Yes, but they are for wood. I don't think it would work in metal. or would it? I know wood working not metal working so I'm clueless on most of this. My new(to me) 1940's lathe is my first step into the balck art of metal working......

                      I'll let you all know how the the square hole turns out.

                      Chris

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                      • #12
                        Hi Chris,

                        I saw some in a catalog a couple of years ago that implied they would work in metal, but I don't remember the details. Couldn't find them with Google, but that's probably because I got so many hits (over 14,000) that I got tired of clicking on links.

                        I would suggest making a brass bushing with the hole in it. Then make the knob, drill a hole large enough for the bushing (without penetrating the knob front), and solder the bushing in place. Pretty simple exercise.

                        For something this small, I would drill out a clearance hole then file the corners square. It would only take a few minutes in brass. You can buy 1/8" square push broaches, but they cost $90. (McMaster-Carr http://www.mcmaster.com catalog page 2398 in the middle)

                        Another option: Make the knob in two pieces, with the front separate from the rear, which has the square hole in it. The above suggestions regarding the hole still apply, but the bushing is now the entire rear of the knob, so no hole is required to accommodate it.

                        I expect the screw was originally an oval head, which fits in a counter-sunk hole but provides a rounded face rather than the more common flat version.

                        ------------------
                        Leigh W3NLB

                        [This message has been edited by Leigh (edited 03-03-2006).]
                        Leigh
                        The entire content of this post is copyright by, and is the sole property of, the author. No assignment
                        of title nor right of publication shall ensue from presentation of this material on any computer site.

                        Comment


                        • #13
                          laying out and working carefuly, you can file a square hole with some needle files. use blue and fit to the square male piece. you can do amazing stuff by fabrication -thats the ticket if its a blind square hole. file the square hole in a small cylinder and soft solder or silver solder into a counter bore. i think basically what Mike said but i may be picturing this piece differently. take some pics, hope that helps
                          .

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                          • #14
                            Rotary broach, aka wobble broach. Drill square, hex, polygons all day long. Tight tolerances and bottom holes too.

                            Make your own. Article in HSM a few years ago, or invent one yourself with a ball bearing and some welding.

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                            • #15
                              This link might be of some use :-

                              http://www.watchman.dsl.pipex.com/tw...er/parser.html
                              Neil B.

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