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  • Butterfy Draw Bar

    I've been thinking about picking up a new 10x54 knee mill to be supplemental to the CNC mills in my shop. I have come to recognize it can do many things the machines I have can't, but I have gotten spoiled. My bigger bed mill (9.5x18 work envelope) and my two main mini bed mills (6.6 x 11.6 work envelope) all have quick change tools. I push a button and the tool holder falls out in my hand. I insert a new tool, release the button, and press start. The other small machine in the shop just gets used for engraving so I never change the tool. Even my CNC knee mill has quick change tooling, although not quite that fast. I change the tool, place a setter on the (part/vise/table) raise the knee until it zeros, remove the setter and press start.

    Anyway, the idea of placing a wrench on a draw bar and maybe a spline wrench with use of my shop ladder just appalls me at the thought of wasted time. Even if I crank the handles or use the power feed. The time wanking on that thread just sounds like it will annoy me.

    I've been thinking about throwing together a butterfly impact drawbar like so many others have done with either a solenoid or a small air cylinder to compress the springs. Because this will be a manual mill I fully intend to use the quill, so the typical loose fitting air cylinder squeezing a stack of belleville washers used on so many small bed mills is not really a good solution. I want something that except for what I want to move stays firmly bolted in place without moving around. I can do that. I've even thought of a quick simple way to engage the quill spline so there is no risk of spinning the quill with the impact and cutting myself. Well the risk of cutting myself is always there, but not from that particular thing anyway. It seems like a pretty decent way to tackle the problem. I should even be able to turn the head without worrying about it.

    I'm curious what problems there could be. I'm sure there is the obvious one of a cheap impact failing quickly. I'll look around for something above the level of a Harbor Freight Central Pneumatic. A long time ago I might have picked Ingersol Rand, but my last couple IR tools/parts have been a little disappointing. To be fair my 1/2 IR impact is pretty much bullet proof. The other issue I see is speed. What other problems do you see?
    *** I always wanted a welding stinger that looked like the north end of a south bound chicken. Often my welds look like somebody pointed the wrong end of a chicken at the joint and squeezed until something came out. Might as well look the part.

  • #2
    We're all different-
    a wrench and a deadblow hammer live next to the mill,
    and I don't mind using them a couple dozen times
    a project.

    But a pneumatic rattle gun? Send me to the dentist!
    I HATE what those things do, to me and to metal.

    I'd be looking for something electric. And being me, I'd
    make it out of a couple old drills or something else I already had.
    'Cause cheapskate!

    t
    rusting in Seattle

    Comment


    • #3
      Originally posted by Tobias-B View Post
      We're all different-
      a wrench and a deadblow hammer live next to the mill,
      and I don't mind using them a couple dozen times
      a project.
      I have same next to the baby mill drill, but I hardly ever use it. Mostly because I have to use the wrench and the dead blow hammer to change tools. There are supplemental jobs I would do on it if tool changes were faster. Beating out a morse taper collet (yeah its one of those) or unlocking a collet closer takes time.
      *** I always wanted a welding stinger that looked like the north end of a south bound chicken. Often my welds look like somebody pointed the wrong end of a chicken at the joint and squeezed until something came out. Might as well look the part.

      Comment


      • #4
        I built a "semi-manual" PDB. I'm tall enough to reach, so I pull the handle down to engage the socket, then swing it left or right to operate it. I'm very pleased. I don't think you need to worry about a spindle lock. The air wrench never turns it at all. I suppose that the drawbar could get seized up in the collet, but that's very unlikely.

        You are right to eschew a cheap HF unit. I had a twenty year old, Taiwan made HF unit, but it was damaged so I bought a new one. Same P/N, about the same price, made in China. The old one was like jewelry in comparison, so I designed my PDB around the damage and used it. The new one sits in my toolbox, for occasional conventional use. Some (e.g. the HF unit) have a machined nose under the rubber guard that make mounting straightforward. I'd suggest you get one with that feature.

        One problem is that I have a couple of sticky tools that don't always release from the taper. It's very annoying because, of course, there's no hammer clearance to tap it loose. I've never found a DIY article or YouTube video that addresses that problem... until yesterday, as luck would have it. This gentleman added a latch to hold the air wrench down, so that the unscrewing drawbar thread can push the tool out. I'll try something like that, and if it works I'll be a happy camper.

        As you've found, there are lots of good ideas out there. A PDB is an excellent project with good return on investment.

        Click image for larger version

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        • #5
          I have a couple Husky (Home Depot brand) air ratchets that are pretty decent. I thought I might look at a Husky, but I'm leaning more towards finding a Chicago Pneumatic. My dad has all Chicago Pneumatic stuff and most of it is as old as I am and still works. Of course checking to make sure modern CP stuff is still as well built.
          *** I always wanted a welding stinger that looked like the north end of a south bound chicken. Often my welds look like somebody pointed the wrong end of a chicken at the joint and squeezed until something came out. Might as well look the part.

          Comment


          • #6
            Been using this shop-built one for 6 or 7 years now.

            http://bullfire.net/Power_Drawbar/Power_Drawbar.html

            Ed

            Click image for larger version

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            For just a little more, you can do it yourself!

            Comment


            • #7
              Originally posted by Bob La Londe View Post
              I've been thinking about throwing together a butterfly impact drawbar like so many others have done
              I think some of them are harsh on the draw bar and spindle. JR

              Comment


              • #8
                Originally posted by Randy View Post

                One problem is that I have a couple of sticky tools that don't always release from the taper.
                A flange on the draw bar and a cross piece with a hole in it should fix that. The draw bar can only lift until it hits, and then it pushes out the tool/holder/collet.

                *** I always wanted a welding stinger that looked like the north end of a south bound chicken. Often my welds look like somebody pointed the wrong end of a chicken at the joint and squeezed until something came out. Might as well look the part.

                Comment


                • #9
                  Originally posted by Bob La Londe View Post

                  A flange on the draw bar and a cross piece with a hole in it should fix that. The draw bar can only lift until it hits, and then it pushes out the tool/holder/collet.
                  Hey now, I like this. It is used on some systems and works. JR

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                  • #10
                    Do guys start the drawbar into the collet by hand, or just trust it to go correctly under power?

                    Comment


                    • #11
                      This is a very interesting discussion.

                      I am curious, why pneumatic instead of electric? Wouldn't a battery powered drill with the built in clutch work? If the battery is the problem, a DC supply would easily solve that.
                      Paul A.
                      SE Texas

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

                      Comment


                      • #12
                        Lower the air pressure?



                        Originally posted by JRouche View Post

                        I think some of them are harsh on the draw bar and spindle. JR
                        Paul A.
                        SE Texas

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

                        Comment


                        • #13
                          Originally posted by Paul Alciatore View Post
                          Lower the air pressure?




                          Yes. I was thinking about the spindle bearings. I have a new set for my spindles I have (AF). Three bearings are expensive.

                          I dont want the hammering that goes with an air tool. Give me a nice DC motor and call it Lunch time. JR

                          Comment


                          • #14
                            Originally posted by JRouche View Post

                            Hey now, I like this. It is used on some systems and works. JR
                            The idea is a variation of the top hat used on spindles with air cylinders to compress the spring without pushing on the bearings.

                            Originally posted by JRouche View Post

                            Yes. I was thinking about the spindle bearings. I have a new set for my spindles I have (AF). Three bearings are expensive.

                            I dont want the hammering that goes with an air tool. Give me a nice DC motor and call it Lunch time. JR
                            Novakon use a motor of some kind to tighten the draw bar on their mills as an option. They also have a lever draw bar of some kind.

                            Other than the locking collar designs like the Kwik 200 most quick changes drawbars seem to use an air cylinder to compress springs of some kind.

                            One outfit uses a long heavy square coil spring and the quill lever itself to spring open a claw for a pull stud on an R8 spindle, but the claw takes up space so you have to use shortened R8 with it. You can pretty much only buy from them unless you are setup to cut off and grind them yourself. When you lift up on the handle it presses the draw bar against a cap which compresses the spring. Might be ok with a TTS style tool holder and a regular collet instead of a claw if the spring is strong enough. If not using the quilll directly you have to lock the quill down slightly so the draw bar doesn't un on the cap. Its a neat idea, but it has its issues...
                            *** I always wanted a welding stinger that looked like the north end of a south bound chicken. Often my welds look like somebody pointed the wrong end of a chicken at the joint and squeezed until something came out. Might as well look the part.

                            Comment


                            • #15
                              I don't know why all the worry about spindle bearings getting wrecked,properly set up the impact only hits for a split second and then its rotational not downward to the bearings,the key is limiting the down travel to allow the drawbar to unscrew 3-4 turns before the head moves upward and bottoms out in the socket pushing the tooling out,works the same but in reverse when installing tooling.
                              I've been using mine for over 15 years and the bearings are still smooth as they were new.
                              There have been jobs in the past they required 50+ tool changes in a day.

                              Short video from way back.

                              https://www.youtube.com/channel/UCro...E5tbx4PkDHtPPw



                              Last edited by J.Ramsey; 02-14-2021, 02:36 PM.

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