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centering 5/64" drill on the thin side of 3/16" steel flat bar.

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  • centering 5/64" drill on the thin side of 3/16" steel flat bar.

    Long time reader, first time poster. I fear this would be better in the "third hand" section but it seems no one uses that section.

    I need to place 5/64" holes every 1/4" or 1/2" on the 3/16" side of some 3/16" x 1/2" on Stainless Steel (304) flat bar. bores are 1/4 to 3/8" deep. (no i can not redesign this project).
    I am using a very old (50's?) rockwell drill press and there is a little play in it. Never bothered me before but this is kinda small tolerance.

    Punching at what looks centered and then drill pressing with a 5/64" bit is not working.
    simply drilling obviously doesn't work as the drill bit walks as i start the bore, even though i have a jig that lets the flat bar slide in a dado cut in a hunk of maple and should keep the bit centered on the 3/16"** side.

    Can someone recommend a tool or a jig or a technique to better center the holes in the side of this ridiculously thin flat bar.
    Please also tell me the secrets of the universe (this is a joke, showing that i realize i am asking for the imposable with the limited equipment i have).

    I have not yet tried the following (which should i try first?):
    -clamping 2 pieces of plate to ether side and using these as brackets for a 3/16"** OD transfer punch. This is time consuming, is a better technique for centering punches out there?
    -inventing a tool that will scour a grove all along in the center of the 3/16"** face. Does such a tool exist?
    -buy shorter drill bits (I am using jobbers) maybe even ones with a stout base.
    -rather than using a punch finding a very stout 60 or 40 degree drill bit to locate my hole, but the play in the drill press is likely too great.
    -building a jig that guides the drill bit, but that would mean i have to mill something with greater precision than i have.
    -buying cold rolled stock as it has a flatter surface than pickled annealed 304 SS.

    EDIT:
    **(THESE VALUES ORIGINALLY READ 3/32 AND WERE REPLACED WITH 3/16" on NOV 27 8am. VALUES WITHOUT ** WERE CORRECT IN THE ORIGINAL POST)
    Last edited by cadmus; 11-27-2012, 10:46 AM. Reason: SEE EDIT NOTE

  • #2
    Cadmus,

    Welcome to the forum. I would probably try to use an indicator to center the stock in a vise and center drill first before drilling. Clamp the vise down once you are centered.

    This is how I have done jobs like this hundreds of times but I always used a milling machine. Not sure if the drill press spindle bearing would be up to the task or not.

    Brian
    OPEN EYES, OPEN EARS, OPEN MIND

    THINK HARDER

    BETTER TO HAVE TOOLS YOU DON'T NEED THAN TO NEED TOOLS YOU DON'T HAVE

    MY NAME IS BRIAN AND I AM A TOOLOHOLIC

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    • #3
      Originally posted by bborr01 View Post
      ..try to use an indicator to center the stock in a vise and center drill first before drilling...
      Thanks,
      What do you mean by "indicator"?
      And what do you mean by "center drill"

      Comment


      • #4
        There's no hope for a drill press without a center punch or spot drill mark. I would make a jig...like a block of hardwood or aluminum with a 3/16 slot and a hole on center that you can use to guide a transfer punch so that your punch marks will be perfect. Make sure you're using a good quality drill....some of the cheapo drills aren't sharpened correctly and tend to cut more on one flute than the other, making the drill pull to one side during the cut.

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        • #5
          An indicator is a Dial Indicator which will tell you where the center is--not useable on a drill press unless you have an x y table vise. The center drill is used in a lathe to drill the hole in the end of a piece of work so that it can be held between centers and turned. They are very stout and will not deflect easliy.

          You might also try a smaller drill to start the hole and then go with the larger size that you want. The larger the drill, the more they wander on start. They will flex, so you can't feed hard.

          Comment


          • #6
            I would scribe a centerline and cross lines for each hole. If you don't have a surface plate you can use a scribe with a sliding block as a guide. Once you have scribed lines you can feel the intersection with a good punch, then centerpunch and you're set.

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            • #7
              I think I would fabricate a jig to slide onto the edge of the bar. Have a piece about an inch wide by maybe 2" long, a paper shim, a piece 3/16" thick by maybe 1/4" wide by 2" long, a paper shin, and another wide piece like the first. Bolt this stack together with a couple of 8-32 screws to form a deep U. Drill the center 3/16" spacer accurately in the center so when the jig is slipped over the bar the hole can act as a drill guide. Just slide it along the bar as you need it. the paper shims should be as thin as possible while still giving enough space for the jig to slide.
              ----------
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              • #8
                Saddle

                The way I see it, you don't have a chance in hell with the equipment you mention. You may get some, but probably not all, especially lined up. You really need a more Ridgid set-up. I'd make a "saddle" with a 5/64 th drill bushing and some way to position it along the bar where it needs to be. McMaster Carr has drill bushings that will work. I would also use a stub length drill, available at the same place. Buy good quality to get the results you need. Bob. SWG beat me to it, same thought but I was thinking milling machine, obviously you do not have one. Drill bushing and stub drill are still good ideas.
                Last edited by Bob Fisher; 11-26-2012, 03:26 PM. Reason: Add

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                • #9
                  Something like this http://www.leevalley.com/en/wood/pag...80,42311,42319 but in the size range you need, use drill bushing...so like # 1, # 3 and # 5 in combo of your suggestions

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                  • #10
                    A hardened drill bushing, align the part correctly under that, maybe an indicator to set the spacing along the length and your good to go. That's what those drill bushings are made for. Maybe a bit of time and materials for the fixture. But it will work no matter how crappy your drill press is. Even a hand drill would do in then.

                    Edit, Russ types faster than I do.

                    Pete

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                    • #11
                      Try something like this............make it out of flat bar and tap the holes for the guides (headless bolts screwed in). Size the center hole for a center drill.


                      http://lumberjocks.com/projects/3186

                      http://toolmonger.com/2009/11/30/ove...center-finder/
                      Last edited by Chester; 11-26-2012, 05:14 PM.

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                      • #12
                        Just my opinion, but always use stub drills if you do not need the depth.

                        (Jobbers drills are way too long for many drilling operations.)

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                        • #13
                          I think your real challenge is going to even be able to drill 304 stainless without destroying the drill bits and/or work hardening the stainless steel bar.

                          1/4" to 3/8" deep?

                          How many you have to drill?

                          Comment


                          • #14
                            Thinking how to make a fixture without a mill. So I found a piece of angle about 1 1/2 x 1 1/2 x 6 inch. Next looked to see what drill bushings I had . Only had 2 that were 3/8 dia . So I found 2 3/8 sq tool bits. I put tool bits next to angle and
                            then set drill bushings on top of tool bits. Next I let them sq up and then used a 3/8 bar with a hole drilled thru and bolted together. Now this should work as a crude fixture to drill a 3/8 part thru center.

                            OP needs 3/16 od bushing with 5/64 id . Mcmaster Carr has them. All he would need is to place his part under bushing against angle part, clamp with c clamp. Then move part and clamp for each hole.

                            Comment


                            • #15
                              Thinking how to make a fixture with out a mill. I had 2 3/8 od bushings so I put them on top of 3/8 wide tools . Then clamped the bushings to a piece of angle with a bar and bolt. Now this makes a CRUDE fixture with center line middle of bushing . OP needs 3/16 od bushing 5/64 id . McMaster Carr has them. He would center bushing over stock then clamp stock to angle move and reclamp over each hole.
                              jimsehr


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