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Twist drill vs spade tipped drill - for holes larger than say 1 inch dia?

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  • #16
    Originally posted by epicfail48 View Post
    Another vote for an annular cutter. Up to about 1.5 inches I know they aren't horrifically expensive, $20-30 for something serviceable. Only downside is annular cutters are depth-limited, so if you need to go deeper than 2 inches that's a problem
    I believe Annular Cutters are available up to 6” long from some companies,I have a couple 3” ones but they are pricey.

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    • #17
      Another vote here for annular cutters! It only hurts once to buy one. Also, there used to be some pretty cheap sets on the internet.
      Vitَria, Brazil

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      • #18
        The only visible difference between annular cutters and hole saws seems to be the flutes on OD, presumably to carry away swarf, assuming they work.

        So ?????????
        2730

        Keep eye on ball.
        Hashim Khan

        Everything not impossible is compulsory

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        • #19
          Originally posted by J Tiers View Post
          The only visible difference between annular cutters and hole saws seems to be the flutes on OD, presumably to carry away swarf, assuming they work.

          So ?????????
          Tiers the annular flutes do there job very well,did a job using the internal portion on some 8’ long rollers. Click image for larger version

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          • #20
            Was thinking the cut geometry looks same, so what makes them work so well is only the swarf removal then? Had to be a reason they work so much better, is that really "all there is to it"?
            2730

            Keep eye on ball.
            Hashim Khan

            Everything not impossible is compulsory

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            • #21
              I would guess so. Packing the flutes of a cutter can stop it cold. If the cutter is compressing chips in the gullet so tight that it can't advance because the chips are squeezed tight between the gullet and the uncut surface, it certainly can't cut any further.

              As far as the spade drills, they shouldn't take a whole lot more horsepower than a twist drill (a little more depending on geometry) but in my experience anyway they do require a LOT more thrust force.

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              • #22
                Originally posted by J Tiers View Post
                The only visible difference between annular cutters and hole saws seems to be the flutes on OD, presumably to carry away swarf, assuming they work.

                So ?????????
                Different tooth geometry and better tolerances help as well. Annular cutters have the arbors built in, essentially, so assuming a quality cutter any runout is going to be a factor of the machine. The annular cutters I've used also have thicker walls than a comparable size of hole saw, makes for a much stiffer tool. It's a bunch of little improvements, but they add up to a much more accurate, cleaner cut.

                To quantify, I've got a .625 annular cutter, when I first got it I sent it through a 1/2" plate to test it. Surface finish was excellent, not bored but miles better than any hole saw, and snap gauges and a mic showed the size as .627". Cut way faster than a hole saw too, since instead of tiny chips I constantly had to retract and clear the saw of, the annular cutter just made long strings that cleared themselves, like a twist drill
                In short, annular cutters ARE just fancy hole saws, but hoo boy are they worth it

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                • #23
                  It will take a lot more pressure if the cutting edges of the teeth are parallel to the surface being cut. Perhaps if you ground a bit of relief on the teeth, the sharp points should engage first and will take a lot less pressure to get the cut started. Might be worth a try.
                  http://pauleschoen.com/pix/PM08_P76_P54.png
                  Paul , P S Technology, Inc. and MrTibbs
                  USA Maryland 21030

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                  • #24
                    Originally posted by J Tiers View Post
                    Was thinking the cut geometry looks same, so what makes them work so well is only the swarf removal then? Had to be a reason they work so much better, is that really "all there is to it"?
                    tooth geometry is very different. On the annular cutters I have each tooth has several different facets. They're more analogous to a drill than to a saw (hole or otherwise). The only downside I've found is that they can generate big birds nests of swarf in alu.

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                    • #25
                      So, re big drilling. I used to always be on the lookout for the biggest drills, and want to just go with the absolute largest drill possible before boring. But now... that just doesn't make much sense. It's just tough on machinery and your wrist. Pop a hole big enough for a boring bar. Set the speed up high and give it the beans. Say you're taking a slug out to 8". 90% of the material is removed with a boring bar anyway, what is a 2" hole vs a 1.5" hole? So that is my new philosophy. Be gentle on the machine unless it is production, let the carbide and power feed do the work, drink beer. Yeah. That's it.
                      21" Royersford Excelsior CamelBack Drillpress Restoration
                      1943 Sidney 16x54 Lathe Restoration

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                      • #26
                        Originally posted by Tundra Twin Track View Post

                        Tiers the annular flutes do there job very well,did a job using the internal portion on some 8’ long rollers. Click image for larger version

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                        Oh yes they do, those drills will eat.

                        I have them from nuthing to two inches. Only used in the Mag Drill. Duh.. JR Nice core bits....

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                        • #27
                          Originally posted by JRouche View Post

                          Oh yes they do, those drills will eat.

                          I have them from nuthing to two inches. Only used in the Mag Drill. Duh.. JR Nice core bits....
                          I've ran a 3 3/8 before in my big drill press. I looked for the pic but couldn't find it. They are sweet. Nothing like a hole saw.
                          21" Royersford Excelsior CamelBack Drillpress Restoration
                          1943 Sidney 16x54 Lathe Restoration

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                          • #28
                            Originally posted by Bented View Post
                            Same machine, 1-7/16 hole with a twist drill in one shot.
                            Power is your friend.
                            https://bented.smugmug.com/My-First-Gallery/i-QpnSStf/A
                            Your posts brought back some old memories. My first paying job after USAF in 1963 was on a W&S #4 with a air operated chuck. I don't remember the size of the spade bit, but it was wider than my hand. Used before reaming the commutator shell for a locomotive traction motor. The machine was a year younger than me with a US Navy plaque on it dated 1942.
                            “I know lots of people who are educated far beyond their intelligence”

                            Lewis Grizzard

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                            • #29
                              Originally posted by Bented View Post
                              Same machine, 1-7/16 hole with a twist drill in one shot.
                              Power is your friend.
                              https://bented.smugmug.com/My-First-Gallery/i-QpnSStf/A
                              Most shops would consider that too dangerous a machine to use with all those long chips.

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                              • #30
                                Originally posted by DR View Post

                                Most shops would consider that too dangerous a machine to use with all those long chips.
                                I should hope not. Have we really become that bad? Drilling is a pretty low speed operation, and although the operator of the machine really should have been breaking those chips, they aren't very dangerous when the tool is not rotating.

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