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  • Bridgeport question for the group

    Got this standard Bridgy POS here and it's getting tiring winding the knee up and down.
    I know you can get these Align units to fit but quite expensive here £350 or around $550 plus 110 volt so need to run a transformer.

    Also read a bit about them being weak on the gearing.

    I have shed loads of 3 phase geared motors and it would be easy for me to fit one on and run it thru an inverter which I have in a small size.

    Problem being there is no easy way to keep manual feed due to the worm drive box and a dog clutch setup starts to get big and messy. My take on it is that I don't need blinding speed and if the gearing is chosen to run at a reasonable rate then the inverter will allow an absolute crawl.

    So my question to the unwashed is "If you have a knee power feed do you use the manual at all or just rely on power ?"
    .

    Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.




  • #2
    Personally I would not want to do without the manual option for fine positioning. What I did was to use an 18V cordless drill if a lot of cranking was needed. I could go up and down several times on one battery charge. You just use an adapter (easy to make) for the drill motor and use it or the crank handle interchangeably.
    Kansas City area

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    • #3
      I use rapid up and down ,under power and a manual feed handle to set and advance the knee for depth of cut . The knee hand feed is used for all cut depth setting.
      Every Mans Work Is A Portrait of Him Self
      http://sites.google.com/site/machinistsite/TWO-BUDDIES
      http://s178.photobucket.com/user/lan...?sort=3&page=1

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      • #4
        Originally posted by John Stevenson View Post
        So my question to the unwashed is "If you have a knee power feed do you use the manual at all or just rely on power ?"
        Oh, so we're the unwashed now, huh? I'll have you know I take a bath once a week whether I need it or not.
        Definition: Racecar - a device that turns money into noise.

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        • #5
          Was I to do such, I think I would employ some sort of differential gearing plan with a couple of brakes. Lock the hand crank and run the motor for power feed. Lock the motor to use the hand crank.

          .......probably too much trouble to build, but would work slick when done.
          Weston Bye - Author, The Mechatronist column, Digital Machinist magazine
          ~Practitioner of the Electromechanical Arts~

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          • #6
            Going back a bit when used one but no way could i live without the manual cranking.
            If you can keep that as well, go ahead.

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            • #7
              Another (harebrained?) idea. Leave the top of the jackscrew alone, but replace the nut support tower with the motor and gearbox turning the nut. As long as the motor is not too strong, you can keep the screw from turning by just holding the hand crank while jogging the motor with the other hand.

              Visions of Sir John being beaten about the kneecaps and nads by his POS Bridgeport (revenge!)
              Weston Bye - Author, The Mechatronist column, Digital Machinist magazine
              ~Practitioner of the Electromechanical Arts~

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              • #8
                someone somewhere posted something about making an adaptor for a battery powered drill ..and just doing it that way

                if you don't fancy battery power you could have air nut driverwith same adaptor on it hanging down on a springy air hose that reels up out of the way

                all the best.markj

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                • #9
                  Don't listen to this talk about fine Z adjustments on your POS Bridgeport. If you need an extra 0.010" depth of cut just use a dull cutter and increase the feed rate until it flexes enough to dig in that extra 0.010".

                  You're welcome.

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                  • #10
                    OK, Like Weston's idea, never thought about that and that's the reason to throw ideas out. Could always have a plunger that locked the horizontal shaft and only disengage it when needing manual but I'm sure I could manage with just power.

                    Bear in mind the motors and gearboxes I have in mind are streets in front of an Align unit.

                    However couple of things, one is I only use the knee for rough positioning and use the quill for putting cuts on as I have a digital display on the quill, machine is imperial but I work 95% metric.

                    Handle on the knee is fixed permanent in that it has a large washer and screw holding it from coming completely off, got smacked in the nose a while ago winding like crazy and it spun off so this makes the drill arrangement tedious plus I want a complete job, everything machine mounted
                    .

                    Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.



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                    • #11
                      I have a Servo 140 (150, I can't remember) unit on my BP knee. it gets used every day, BUT, the last few thou or for "fine" adjustment is always by the handwheel.

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                      • #12
                        OK - now that we have the full story it's back to the drawing board for a redesign!
                        In that case, an easy fix would be to replace the hand crank with a gear motor, the motor hanging vertical off the left side. A momentary switch in a convenient location would polish it off. That would make an easy install and maintenance with the motor pretty much out of the way.
                        Edit to add - You could hold the gear motor on with the bolt and washer already there and appropriate spacers on the drive shaft.
                        Last edited by Toolguy; 12-22-2012, 11:13 AM.
                        Kansas City area

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                        • #13
                          A vee belt and pulley system could give you a drive with easy de-clutch capability.
                          Don Young

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                          • #14
                            Actually... experiment with the vfd "jog" function. With gearing it might be able to be set so that it say 1/2 thou per hit, or even a 10th or so if you gear low enough

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                            • #15
                              If you just want traverse up and down without feeds consider this:

                              http://www.ebay.com/itm/NEW-STEEL-GE...item563d0ffde9

                              This gadget engages the knee face clutch. Add a machined piece that slps over the pilot diameter arrenged with an extended flatted shaft so you can drive it with a 1/2 V/S drill. Dedicate the drill to this service so whenever you need to position the knee you grab the drill and buzz it to whatever height you need. Maybe if the drill is sensitive enough you can use it for power feed but it would be awkward.

                              I saw a flurry of such gadgets in the last year or so but I could find no references.

                              Next step is buy a Servo syle knee feed unit. I have one but it's slow.

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