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Can indexable drills damage an old manual lathe?

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  • Can indexable drills damage an old manual lathe?

    I have the opportunity to get some Komet indexable drills ranging in size from 0.625" to 1.375" in diameter. I plan on making a holder out of a CA series boring bar holder so that I can run compressed air through the drills. Coolant is not an option because of the mess so the only material the drills will see is plastic. I have a 1930's 16" South Bend "O" series lathe with bronze headstock bearings. The motor is a 3HP Lima Gearshift motor with flat belt drive. On a lathe this old is it possible that I will damage the bronze bearings using indexables. I have only used these types of bits on Mazak CNC lathes so I might not even have the power on my South bend to run them. I AM NOT doing production work so using the bits to full capacity is not important.

  • #2
    I occasionally use similar 1" and 1-3/8" Valenite Val-U-Dex insert drills on a Victor 1640 manual lathe, holding them in a CA size QCTP #4 boring bar holder. The only problem I had was trying too much feed rate in some nasty steel. The QCTP started to rotate around on me. I backed off to just under .002" per rev feed rate and I was OK, but I may pin the QCTP block to the compound slide to prevent that.

    If you're cutting just light materials, the straight-on forces aren't going to hurt anything, Having enough power might be the bigger issue.

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    • #3
      You mentioned you planned to cut plastic- that requires really sharp inserts, which you can get for some indexable endmills and lathe tools, the ground and polished inserts for aluminum are sharp enough to use on plastic.

      But in my experience those kinds of inserts aren't available for indexible drills, which are most commonly used on steels and thus need coated inserts that usually aren't that sharp.

      So before popping for these drills I'd check to see what kind of inserts you'll be able to get for them.

      Paul T.
      www.power-t.com

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      • #4
        Indexable Drill

        I use that kind of drill fairly often on steel and alum. They seem to me to take less HP than a similar size twist drill. They work fine on my 2 HP 12 X 40 Import lathe and Bridgeport head mills. I have a 2" diam. one I use to drill a 2" hole in solid alum. on the mill with no pilot hole. As for inserts, you can get uncoated ones and grind a little more back clearance on and make an upsharp edge at the same time. Or you could make your own out of tool steel and harden it. They would probably cut OK as is though.

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        • #5
          Originally posted by Chris165
          I have the opportunity to get some Komet indexable drills ranging in size from 0.625" to 1.375" in diameter. I plan on making a holder out of a CA series boring bar holder so that I can run compressed air through the drills. Coolant is not an option because of the mess so the only material the drills will see is plastic. I have a 1930's 16" South Bend "O" series lathe with bronze headstock bearings. The motor is a 3HP Lima Gearshift motor with flat belt drive. On a lathe this old is it possible that I will damage the bronze bearings using indexables. I have only used these types of bits on Mazak CNC lathes so I might not even have the power on my South bend to run them. I AM NOT doing production work so using the bits to full capacity is not important.

          Short answer NO

          In the 1800s they were using similar'ish lathes, with similar'ish drills (spade drills), no problems.

          The cut is balanced so no great side forces, as you are cutting plastics -no huge thrust forces either.

          Your problem maybe lack of power - flat belt slip
          John

          I used to be indecisive. Now I'm not so sure , but I'm not a complete idiot - some bits are still missing

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          • #6
            The sharpest insert for those drills would likely be a Valenite WCEM321 1P grade UK20. Substitute the size (the 321) for whatever size insert the drill requires, but do look for that 1P chipbreaker and the uncoated UK20 grade. Those will work best in aluminum, plastics, other non-ferrous metals, and cast iron.

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