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Kinda OT - Drilling 1" hole in .5" Steel Plate

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  • Kinda OT - Drilling 1" hole in .5" Steel Plate

    I need to drill several holes, 1", 1-3/8" in 1/2" steel plate. I have a 16 speed drill press. What is the best way to do this? I have a Spectrum 375 plasma, but these need to be super clean holes. Can I use an end milling bit in the drill press, use a low speed and cutting oil and just go slow? something like ....

    http://www.grizzly.com/catalog/2009/Main/619

    I really don't want to take it to a machine shop. Even if I spend as much on a milling bit as I would to pay the shop, I'd like to do it myself.

    Any suggestions would be appreciated.

  • #2
    Personally I would use a hole saw for a few holes. How many do you actually need by the way? Slow speed with the drill press & a low stream of compressed air on the edge of the hole clears chips & helps keep cutter cool. MAKE sure you wear a shield or goggles with the air as both eyes are a bonus. Good luck with your project.
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    • #3
      i use carbide tipped hole saws for my 3/8" stainless plate. it takes a good 5 minutes for each hole but ive cut about 18 of them with my 1.5" hole saw and the tool is still in good shape. i buy them from fastenal, they are $25-$45 depending on the size. you have to make sure you tell them that you need a carbide tipped hole saw or else you will get a cheap wood saw that will be destroyed 30 seconds into the cut. you need to cut them at about 80-100 rpm with a good amount of lube.

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      • #4
        A bi-metal hole saw with a pilot bit will work fine.

        Use 350RPM for the 1" and 250RPM for the 1 3/8"

        Use a coolant... water based is cheapest, keeps the tool coolest, and prevents the teeth from sliding across the surface. I make a coolant out of 5 parts water, one part Murphy's oil soap and 1 part mineral oil. The soap and oil are just to prevent rusting.

        Don't use motor oil or WD-40.

        Make sure all parts of your drill press are tight and clamped, and firmly clamp the workpiece to the table. Use firm, steady pressure and never allow the hole saw to drag the surface without pressure.

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        • #5
          Using an end mill will require a pilot hole, or it's gonna be even slower than using a hole saw (assuming you're using a center cutting end mill). Once you pilot it with the plasma, you won't have any true center reference for the end mill.

          How many of these? 1/2" material isn't really all that much to remove. A silver and demming 1" twist drill only costs about 20 bucks.
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          • #6
            A hole saw will not give you a clean hole like a twist drill bit will.
            The key to drilling large holes is to use as low a speed as possible and have the horse power to turn the bit.

            As an example........ I drill 1-1/8 inch holes in steel plate with no problem. They are clean as a pin. The pic below is an aluminum plate, but it does an equal job on steel..... I just have to use cutting oil on steel plate. The slow speed just brings a long continuous spiral of metal out of the hole. Fun to watch...........



            The drawback is that this is done on my Bridgeport mill with it in backgear.
            Backgear gives me about 25 rpm and loads of increased torque, along with having a 2HP motor on the mill.

            Unfortunately, I do not believe you will have much success using a drill press. At the slowest setting it will still be way too much rpm to drill this kind of hole through plate.

            You can try, but good luck on it. The Bridgeport is 2200 lbs of cast iron sitting there, so it has the HP, the gearing, and the mass to do this kind of thing............ pg


            Originally posted by BMS View Post
            I need to drill several holes, 1", 1-3/8" in 1/2" steel plate. I have a 16 speed drill press. What is the best way to do this? I have a Spectrum 375 plasma, but these need to be super clean holes. Can I use an end milling bit in the drill press, use a low speed and cutting oil and just go slow? something like ....

            http://www.grizzly.com/catalog/2009/Main/619

            I really don't want to take it to a machine shop. Even if I spend as much on a milling bit as I would to pay the shop, I'd like to do it myself.

            Any suggestions would be appreciated.
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            • #7
              i agree with piniongear, slower is better. i forgot to mention that i use my bridgeport as well to get about 60 rpms with the carbide hole saw. i dont use a twist bit because for a 1.5 inch i can only find them for around $130. you could always get a drag cup for your plasma cutter and make a round template to trace. if you have a steady hand and your air is dry then it should come out pretty good. you could go in with a cylindrical burr and smooth it out if you have to.

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              • #8
                For a limited amount of holes I opt for the hole saw route. The fastest I cut on this job was 35 seconds but I was testing to see what it could be done in. My neighbor recently did 3/8 plate, 1 3/8, said it took him about an hour to do 20 or so and the bit is still usable.
                In the second pic I did them in place, these were 3/4 thru 2 plates half inch thick, using water and taking break, about 5 minutes a hole.
                Attached Files

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                • #9
                  excellent feedback. I guess I just couldn't imagine a hole saw doing that kind of work. sometimes I tend to think of too many fancy-pants ways to do things I think. usually how I end up with so many tools that are only good for one specific task! Guess I'll practice on a couple pieces with some bits and a hole saw.

                  I need to drill about (12) 3/4" holes in some 1/4" steel tube and only about 4 or 6 (total) of the 1" or 1-3/8" holes in 1/2" material.

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                  • #10
                    Hole saw will give you a hole, but not to close tolerances, they wobble too much. Tight hole, need either an annular cutter, or drill bits.

                    Easy to do with drill bits, first a pilot, probably 1/4 inch max, more likely 3/16. Then go right in with your finish size, assuming you have properly sharpened bits. Coolant, forget about cutting oil, use water soluble oil. It needs to be white, some brands, some hard waters, you need to mix with hot water, or add additional soap, to get the proper emulsion. Staylube is crap, Lubriplate is good. Keep it doused, you can't use too much. I use the cheap pump spray bottles, get them 3 for $2.99 or something, at the drug store.

                    A good, properly sharpened bit, and properly cooled bit, with proper down-pressure, will make chips, not spirals. Spirals is an indication, you have slightly offset cutting edges on your bit. Still works, but not quite correct.
                    Obviously, I'm just a hack-artist, you shouldn't be listening to anything I say .....

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                    • #11
                      You could rent one of these.

                      Caution!
                      These are "my" views based only on “my” experiences in “my” little bitty world.

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                      • #12
                        Don't know how "clean" you're after, BMS, but to me, clean holes are made with a slightly undersized drillbit and finished with a chucking reamer, maybe even two stages of reaming.

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                        • #13
                          smitty - good thought. I'd like for them to be near perfect. I figure I'll aim high. Looks like Grizzly tools sells large chucking reamers for ok $$$.

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                          • #14
                            Originally posted by Sonora Iron View Post
                            You could rent one of these.

                            +1
                            And what piniongear said ++1

                            Keep in mind that reaming of holes this big will require drilling the holes considerably undersize due to using a drill press. i.e. 1/16" and at that point your reamer will be taxed to the max because they are not designed to remove more then about 1/32" at the most. A drill press doesn't have the mass to drill a good straight hole when it's this big The spindle will flex and your holes will be off shaped That's if your drill press will go slow enough to even attempt.
                            Find someone with a mill close to you that works in trade or for beer.
                            Last edited by kcstott; 08-31-2009, 02:54 PM.
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                            • #15
                              Its good to know what the project is, not every hole needs to be perfect. The ones on that green machine in the pic are way better from a hole saw than the factory ones were, by far, almost a full drill size.

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