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Power tapping 1/2" mild steel plate

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  • #16
    Originally posted by PT Doc View Post
    I drilled 5/16 for all of them for the 3/8-16 end thread. Tapping head seems like the best option. Another option that was recommended was a cordless drill. I just might try that since it has a clutch and can reverse and will save me all the hand tapping. Thanks for the help.

    A "good" tapping head is expensive. Do your current and future needs justify that? I don't know the "import" market in tapping heads, anything worthwhile for less?

    You can also use a corded variable speed reversing drill motor. Keeping the tap aligned perpendicular to the plate surface is the issue there. I've seen guys use a guide block to help with straightness in tapping. Drill a 3/8 through hole in a block to use as a method of aligning the tap while running it in.

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    • #17
      Tapping heads come and go on eBay all the time. They range widely in price depending on starting price and who is bidding. A used one that will do up to half inch is usually in the lower price range. One of my favorite ones is Ettco-Emrick. They look kind of funny but really work well.
      Kansas City area

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      • #18
        +1 on the cordless drill. I rarely get the tap wrench out for anything larger than m3 upto m10 or m12.
        I use serial taps, cos thats what Ketan sells, and they work. Dip in Trefolex tin, bosh into hole, reverse out, repeat.
        Dave
        Just south of Sudspumpwater UK

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        • #19
          I have/had a set of ettco heads I got off ebay. I think I picked up the big and little one for about $50 for both.

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          • #20
            I'd do it without question on a 3ph powered mill but never on a drill press at 300 RPM unless I had a lot of extra and expendable taps.

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            • #21
              Originally posted by DATo View Post
              I'd do it without question on a 3ph powered mill but never on a drill press at 300 RPM unless I had a lot of extra and expendable taps.
              People tap with tapping heads on drillpresses all the time.I looked at Kennametal site and they say it takes 0.4hp for 3/8-1y tap on mild steel(which i do not believe very much). I know for a fact that most of the "entry level" drillpresses with puny motors can not tap a 3/8 hole in steel.

              I find most often however its the belt that starts slipping.
              FSWizard - Free Online Speed and Feed Calculator

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              • #22
                Several posters mention 300 rpm as too fast. If it's beyond a person's comfort level, okay, go slower. But, 300 rpm is perfectly within reason, even a bit slow for production work. Example, I have a special purpose tapping machine in my shop. It uses change gears for each thread pitch. The machine's rated capacity is 5/16"-18 in mild steel and the interesting thing is the lowest rpm is 1000. I don't have change gears for 16 pitch, I've done 3/8-24 though at 1000 rpm.

                Just as a matter of curiosity.....I have some special purpose taps with reduced shank diameter. The shank diameter is small enough so the tap can drop through a tapped hole. They can be used in non-reversible spindle machines. They use a slip fit driver in the machine spindle for the tap's square end. Position the tap drilled hole under the machine spindle. bring the machine quill down with the tap point in the hole and the driver catching the end of the tap. Turn on spindle and downfeed the tap all the way through the material and the tap falls out of the driver. This was used for large hole tapping.

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                • #23
                  where can I post a want to buy thread for a tapping head with capacity to 1/2" with a straight shank? randomly buying on eBay from an industrial reseller fit a used tapping head doesn't sit well with me for some reason. thanks for the help

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                  • #24
                    I put together a hodge podge of a tapping machine. I started with a cheap Chinese bench top drill press. I changed the motor to one with a gear reduction. I mounted a tapping head in the spindle. Then I fitted it with a Bilz tapping chuck. The best part is the vise I use to hold the workpiece. It is mounted on a electromagnet operated with a foot pedal. The vise/magnet slide around on the table of the drill press. When I lower the tap to the hole and it centers I then step on the foot pedal to hold the vise down to the table so when I reach the bottom of the hole and let the spindle retract to reverse the tapping head the vise doesn't raise with the tap. It works great for tapping holes very fast. I don't run it at high RPM's maybe 150 but it goes real quick with not much pause between each hole.
                    Location: The Black Forest in Germany

                    How to become a millionaire: Start out with 10 million and take up machining as a hobby!

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                    • #25
                      Originally posted by Zero_Divide View Post
                      People tap with tapping heads on drillpresses all the time.I looked at Kennametal site and they say it takes 0.4hp for 3/8-1y tap on mild steel(which i do not believe very much). I know for a fact that most of the "entry level" drillpresses with puny motors can not tap a 3/8 hole in steel.

                      I find most often however its the belt that starts slipping.
                      I totally agree, but the original post did not mention access to a tapping head, just a drill press with a minimum speed of 300RPM.

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