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  • boring a smooth hole...

    I'm trying my hand at making a set of swaging dies for 45 acp projectile. That would be .451 in diameter. As my limited knowledge says to me that to make the best (read smoothest finish) precise hole would be to use a reamer to finish the hole.

    I've found a .451 chucking reamer on line. And in my Machine tools, and machining practices handbook, it states that the hole be drilled .001-.006" smaller than said reamer. Now my drill chart shows the nearest drill to be a 7/16" which is .013" smaller.

    Can someone please school the amateur how this is to be accomplished

    Thanks in advance
    Brock in AR

  • #2
    Drill 7/16, use a boring bar in lathe or mill to go to about .005 under, then ream on slow speed - 90 to 125 rpm. It's probably best to ream to .450, harden the die and lap the last thou. after heat treat.

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    • #3
      Originally posted by elginrunner View Post
      I've found a .451 chucking reamer on line. And in my Machine tools, and machining practices handbook, it states that the hole be drilled .001-.006" smaller than said reamer. Now my drill chart shows the nearest drill to be a 7/16" which is .013" smaller.
      drill 7/16, .013 is on the small side of reamer allowance - 1/64 - 1/32 is common depending on size. Something is not right with the .001-.006" smaller advice, could it be .01 - .06"? odds are pretty good that any drill will drill at least several thou larger than its nominal size.

      You could bore it in the lathe and save buying an odd sized reamer
      .

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      • #4
        I don't think .013 is too much to ream. I usually aim for something in the range of .020. As was mentioned, most drills will drill oversize anyway. When I need a hole on size and don't need to ream,I drill about .025 under and finish with the proper size. I always check a drill with a mike if it's important. Wouldn't be the first time a drill was not replaced in it''s proper slot. Bob.

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        • #5
          If you only drill and then ream, the reamer will follow the drilled hole (obviously ) and if your drill walked alittle (even using a center drill first) the reamer will follow that.
          If you really want to ream (and not just drill and bore) and squarness is important; i too would go with drill, bore then ream.
          ~ What was once an Opinion, became a Fact, to be later proven Wrong ~
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          • #6
            thanks, for the info guys, looks like a boring bar is in my future.

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            • #7
              What, nobody uses those nice pre-reaming tools that are like drills but with three flutes? What are they called in english, as I only know their finnish name? For example, making a 12H7 hole: drill 11 mm, use the three flute drill to straighten the hole and to make it 11.75 mm, then ream with 12H7 reamer.
              Amount of experience is in direct proportion to the value of broken equipment.

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              • #8
                I suspect that even a reamed hole isn't going to be smooth enough for a swaging die. I think you'll need to lap it. Look up "barrel laps." I'd be tempted to ream 0.450" and lap to final size with #240, #320, and #600 abrasive. You might be able to ream 0.4505" and start with #320. If you decide to try lapping, go easy on the amount of abrasive. If there is too much it tends to produce a bell-mouth hole.
                ----------
                Try to make a living, not a killing. -- Utah Phillips
                Don't believe everything you know. -- Bumper sticker
                Everybody is ignorant, only on different subjects. -- Will Rogers
                There are lots of people who mistake their imagination for their memory. - Josh Billings
                Law of Logical Argument - Anything is possible if you don't know what you are talking about.
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                • #9
                  Originally posted by elginrunner View Post
                  I'm trying my hand at making a set of swaging dies for 45 acp projectile. That would be .451 in diameter. As my limited knowledge says to me that to make the best (read smoothest finish) precise hole would be to use a reamer to finish the hole.
                  Are you swaging bullets, or resizing cast bullets? Either way, I think you would want a really, really smooth metal finish on your die. I would drill, bore, ream and then polish with Flitz or toothpaste on a felt mop.

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                  • #10
                    L&I, a well known reamer manufacturer has the following information in their catalog regarding the amount of stock removal for reamers.

                    Up to and including 1/16" - .003 to .005"

                    Over 1/16 up to and including 1/8" - .004 to .008"

                    Over 1/8 up to and including 1/4" - .006 to .012"

                    Over 1/4 up to and including 3/8" - .008 to .014"

                    Over 3/8 up to and including 1/2" - .010 to .015"

                    Correct size hole would then be .461 to .466. You could drill slightly oversized, as previously recommended with a 15/32" (.4688) or
                    purchase an 11.7mm (.4606) or an 11.8mm (.4646) drill. You decide.

                    Ed P

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                    • #11
                      0.461" would be oversize for a 0.451 swaging die. I have made sizing/lubricating dies by boring and reaming with an expansion reamer (not the blade type). I will finish to size with a barrel lap.

                      Depending on your application and the nature of the alloy you are using, the end product might not be the exact dimension of the die, it could be slightly over or undersized.

                      In reply to your other thread, I use Everede boring bars with HSS inserts ground with a slight nose radius. They leave a good finish.
                      Jim H.

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                      • #12
                        Originally posted by SGW View Post
                        I suspect that even a reamed hole isn't going to be smooth enough for a swaging die. I think you'll need to lap it. Look up "barrel laps." I'd be tempted to ream 0.450" and lap to final size with #240, #320, and #600 abrasive. You might be able to ream 0.4505" and start with #320. If you decide to try lapping, go easy on the amount of abrasive. If there is too much it tends to produce a bell-mouth hole.
                        This is good advice. You are going to want to lap it to a mirror finish or you will have rough looking bullets and be shaving lead. Ream or bore to .001-.002" undersize depending on the finish you can attain and then take the rest out with successively smaller lapping grits. If you do a search on castboolits.com, I think the process for making sizing dies has been explained a few times.

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                        • #13
                          About the lapping/honing of holes, a quick and easy way is to take a piece of copper or brass pipe (rod goes too, but is harder to get off if something goes wonky), turn down the OD to the finished size minus 0.1 mm, then put the tube in a hand drill, attach your workpiece to something solid, apply honing/lapping compound on the tube and fire away from the back side of your workpiece. Clean with a solvent (the stuf I'm using washes away with water), check with a proper sized pin or rod, rinse and repeat if necessary.
                          Amount of experience is in direct proportion to the value of broken equipment.

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