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Great Drill Bits for plastic

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  • Great Drill Bits for plastic

    I got these Drill Bits at Auction and real impressed how they work in plastic,drilled 3-1/4” depth in one stroke no pecking,5/32 @ 850 rpm. Click image for larger version

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  • #2
    Is that one of those parabolic flute deals? I've heard nothing but good about them. Kinda rich for my blood though.
    25 miles north of Buffalo NY, USA

    Comment


    • #3
      Is plastic a recommended use for parabolic flute bits? With their large rake angle I am surprised that they do not grab like crazy in soft materials like plastic. Your photo seems to show a blind hole being drilled or at least one so deep that the sides of the drill bit will provide a lot of friction when it breaks through. Have you tried these on through holes in thinner plastic? 1/8", 1/4"? How do they handle the break-through situation then?

      I have a set of bits where I reduced the rake angle to zero. They are the ones that I reach for first when drilling softer materials like brass and plastic.
      Paul A.
      SE Texas

      And if you look REAL close at an analog signal,
      You will find that it has discrete steps.

      Comment


      • #4
        No idea about the flute cross section but the lower helix angle would certainly clear chips better. Especially on fluffy plastic work. Nice score ! ! !

        At the other end though the lower helix angle might make it have a more aggressive bite into the plastic. Does the cutting edge have a small neutral or negative top rake angle of any sort?

        Adding such a small flat (shown on one of my modified drill bits used for plastics and brass) is my #1 favorite drill bit modification. I keep a separate drill index to hold the ones I've modified like this. It's already got all the more popular sizes and gets a new one each time I need it.

        For anyone wondering this is a 29/64" size and the flat shown is roughly.025'ish from a quick check with a dial caliper. Smaller size drills tend to see me putting on a .015 to .02 flat.

        Click image for larger version

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        Chilliwack BC, Canada

        Comment


        • #5
          Nice! They do look like parabolic flutes which are supposed to be good for deep holes. I have never used one though...

          Comment


          • #6
            Yes that is a parabolic flute drill. I used to use them drilling deep holes for aluminum air manifolds. Worked much better than standard twist drill

            Comment


            • #7
              Originally posted by Paul Alciatore View Post
              Is plastic a recommended use for parabolic flute bits? With their large rake angle I am surprised that they do not grab like crazy in soft materials like plastic. Your photo seems to show a blind hole being drilled or at least one so deep that the sides of the drill bit will provide a lot of friction when it breaks through. Have you tried these on through holes in thinner plastic? 1/8", 1/4"? How do they handle the break-through situation then?

              I have a set of bits where I reduced the rake angle to zero. They are the ones that I reach for first when drilling softer materials like brass and plastic.
              If the spindle feed is under control and the parts are well held no drill will ever take off on you, purposely dulling a $40.00 drill is counterproductive at best. This is the year 2021 not the year 1921 (-:
              Last edited by Bented; 07-15-2021, 09:06 PM.

              Comment


              • #8
                Originally posted by nickel-city-fab View Post
                Is that one of those parabolic flute deals? I've heard nothing but good about them. Kinda rich for my blood though.
                There were pretty cheap in Auction Goodies probably less than jobber length at hardware store.
                Originally posted by Paul Alciatore View Post
                Is plastic a recommended use for parabolic flute bits? With their large rake angle I am surprised that they do not grab like crazy in soft materials like plastic. Your photo seems to show a blind hole being drilled or at least one so deep that the sides of the drill bit will provide a lot of friction when it breaks through. Have you tried these on through holes in thinner plastic? 1/8", 1/4"? How do they handle the break-through situation then?

                I have a set of bits where I reduced the rake angle to zero. They are the ones that I reach for first when drilling softer materials like brass and plastic.
                I will try anything once and Drill Bits are one of those tools if price was very reasonable,I used a bunch of those Aircraft Drill Bits with 1/4” NF threads on shank on steel a year ago repairing Grain Dryer and there designed for Aluminum.They worked like a Champ.
                Originally posted by garyhlucas View Post
                Yes that is a parabolic flute drill. I used to use them drilling deep holes for aluminum air manifolds. Worked much better than standard twist drill
                Thanks I was wondering if that was what there called.

                Comment


                • #9
                  Originally posted by Bented View Post

                  If the spindle feed is under control and the parts are well held no drill will ever take off on you, purposely dulling a $40.00 drill is counterproductive at best. This is the year 2021 not the year 1921 (-:
                  Tell that to the guy trying to use a hand drill on a piece of acrylic because he's fresh out of milling machines. A two minute mod to give the cutting edge the neutral or slightly negative top rake prevents the drill from spalling out the other side or diving in and wedging tight and cracking the plastic. Things that can also happen far too easily on a drill press too for that matter.

                  Hey Paul, I posted my reply thinking that no one had wondered the same thing. Looks like we were both thinking the same thing since our posts asking the same question are only a minute apart. Great minds and all that perhaps? ... If only I didn't take a couple of minutes to take that picture of the drill bit....
                  Chilliwack BC, Canada

                  Comment


                  • #10
                    I fully understand the concept of a sharp drill corkscrewing into the work, have not had that happen in over 20 years or so,
                    Have also never ground a new drill dull (-:

                    Last week I turned 31 ft. of 304 stainless into chips using a single HSS .656" drill, this was a slow process at best.
                    Last edited by Bented; 07-16-2021, 01:16 PM.

                    Comment


                    • #11
                      Originally posted by BCRider View Post
                      No idea about the flute cross section but the lower helix angle would certainly clear chips better. Especially on fluffy plastic work. Nice score ! ! !

                      At the other end though the lower helix angle might make it have a more aggressive bite into the plastic. Does the cutting edge have a small neutral or negative top rake angle of any sort?

                      Adding such a small flat (shown on one of my modified drill bits used for plastics and brass) is my #1 favorite drill bit modification. I keep a separate drill index to hold the ones I've modified like this. It's already got all the more popular sizes and gets a new one each time I need it.

                      For anyone wondering this is a 29/64" size and the flat shown is roughly.025'ish from a quick check with a dial caliper. Smaller size drills tend to see me putting on a .015 to .02 flat.

                      Click image for larger version

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                      modifying rake angle in drill bits. This is an excellent method. I suggest naysayers are inexperienced.

                      Comment


                      • #12
                        Originally posted by strokersix View Post

                        modifying rake angle in drill bits. This is an excellent method. I suggest naysayers are inexperienced.
                        No, it really does work I had to learn that one the hard way. Ever try drilling in copper without grabbing, you have to dull off the edges a bit with a stone.
                        25 miles north of Buffalo NY, USA

                        Comment


                        • #13
                          Originally posted by Paul Alciatore View Post
                          Your photo seems to show a blind hole being drilled or at least one so deep that the sides of the drill bit will provide a lot of friction when it breaks through. .
                          Sorry Paul for not fully explaining pic,5/32” hole was drilled first then hole was countersunk with U drill bit,I usually do the finish cuts last. Click image for larger version

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                          • #14
                            Changing the rake angle on a cutting tool does not mean it will be dull. There are many inserts that have a zero degree rake and even negative rake angles. They are still quite sharp.



                            Originally posted by Bented View Post
                            I fully understand the concept of a sharp drill corkscrewing into the work, have not had that happen in over 20 years or so,
                            Have also never ground a new drill dull (-:

                            Last week I turned 31 ft. of 304 stainless into chips using a single HSS .656" drill, this was a slow process at best.
                            Paul A.
                            SE Texas

                            And if you look REAL close at an analog signal,
                            You will find that it has discrete steps.

                            Comment


                            • #15
                              Yes, your photo illustrates my/our point in an excellent manner. That is exactly what I did with my set of bits. I was too lazy to add a photo so your post is better then mine.

                              Yes, great minds...



                              Originally posted by BCRider View Post

                              Tell that to the guy trying to use a hand drill on a piece of acrylic because he's fresh out of milling machines. A two minute mod to give the cutting edge the neutral or slightly negative top rake prevents the drill from spalling out the other side or diving in and wedging tight and cracking the plastic. Things that can also happen far too easily on a drill press too for that matter.

                              Hey Paul, I posted my reply thinking that no one had wondered the same thing. Looks like we were both thinking the same thing since our posts asking the same question are only a minute apart. Great minds and all that perhaps? ... If only I didn't take a couple of minutes to take that picture of the drill bit....
                              Paul A.
                              SE Texas

                              And if you look REAL close at an analog signal,
                              You will find that it has discrete steps.

                              Comment

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