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Clutch on lathe power feed shaft

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  • Clutch on lathe power feed shaft

    My CX701 lathe by Craftex seems to be a very good working lathe, and I am quite happy with it. The only thing that concerns me is that there is no clutch on the power feed shaft where it exits the gearbox at the head of the lathe, only a brass shear pin. It is my fondest hope that I never get to see if that shear-pin really will protect the rest of the drive train in the lathe if I should do something dumb like run the tool into a shoulder on a turned shaft in power feed mode. I know that other lathes have a slip clutch on that shaft. Does anyone know if there is a slip clutch available for lathes that can be retrofitted to that shaft as an aftermarket kind of thing?---Brian
    Brian Rupnow

  • #2
    Brian,

    I'm not familiar with your particular lathe, but from what I see, it has a separate leadscrew & power feed shaft.

    Is there an adjustable clutch built into the saddle, that automatically drops power feed out at a certain load? Mine has this, and it allows me to power into the bedstop when machining to a shoulder.

    Ian
    All of the gear, no idea...

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    • #3
      On my Leblond regal The lead screw and feed shaft both have ball detent clutches. I would think with a little work, You should be able to fit the same to your lathe in place of the shear pin.

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      • #4
        Mine has no clutch. period.--That's why I'm asking bout a clutch that I can retrofit.
        Brian Rupnow

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        • #5
          I know where this is going.lots of amazing cad drawings .There must be alot of online downloadable drawings of existing clutches. I wonder how or if my lathe has also got this .I better go look. (emco v 13)

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          • #6
            Well, you can buy or build. The principles seem fairly simple http://mechanical-design-handbook.bl...-overload.html so making your own should be quite possible. Having looked a little at prices, new would seem to almost double the cost of your lathe.

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            • #7
              Hi,

              If you need the clutch, you are doing something wrong.

              The brass pin is much cheaper than a full blown dog clutch. Which was easier on your wallet. And it WILL do the job properly. Shear pins are used in many applications and from my experience are often more reliable than a clutch. So I wouldn't be concerned. You should be paying enough attention to not crash anyway. And if you should be that unfortunate, just don't use a dowel pin as a substitute.

              Dalee
              If you think you understand what is going on, you haven't been paying attention.

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              • #8
                Note that even lathes with clutches don't use them when threading, and the carriage is moving much faster then. May as well develop the reflexes.

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                • #9
                  Don't worry about the shear pin. I was being stupid one day and grabbing the handwheel on my 12x36 while the lathe was in power feed and giving it extra resistance for kicks and giggles, seeing how much torque it had... And then the shear pin broke and the whole power feed axle popped out the right side mount, freeing the carriage to move as it wished.

                  So yes, it will definitely shear before anything else is damaged, and does not take much torque at all to shear that little pin. A crash or feed to end will definately shear it no problem at all.

                  I took the shear pin out, and stuffed it back in the other side of the hole since I didn't have a spare. Still works just fine, haven't sheared it again even though its now only going through 1 of the 2 'holes'

                  PS: I once accidentally turned my lathe on the wrong way while threading, starting at a shoulder...
                  it *displaced* 0.1" of aluminum with the turning tool and seemed very happy to do it. Sorta like roll threading except the resulting thread was wayyyy too high.

                  Id wager if you accidentally power feed into a shoulder, that shear pin will snap or it will happily turn the shoulder off for you.
                  Last edited by Black_Moons; 01-16-2016, 02:35 PM.
                  Play Brutal Nature, Black Moons free to play highly realistic voxel sandbox game.

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                  • #10
                    Eugene, our V13 has a clutch on the feed-shaft, which is adjustable and a shear pin on the lead screw.

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                    • #11
                      The Emco V10 also has a small clutch, maybe 1 inch diameter x 2 inches(?) Very nice. You can even use it to power feed to a stop, and I did! (from the manual) but I doubt it would last to long if you did a lot. Just a series of slips disks and a preload spring. Easy to make and retrofit. It goes directly inline with the power bar (not the lead screw). There are couple of v10s being parted out on ebay - contact the seller and ask if they still have the part - probably didn't occur to them to list it.

                      My big lathe has a ratcheting overload; saved my butt a couple of times. it's not for use to a stop, but for emergencies. You can have the best reflexes in the world, but inattention will still get you. In my case it was two fold : long fine repetitive power feeds that "allowed" me to not watch every second. Bad, but... AND the other time... slamming the "wrong" lever. lol
                      Last edited by lakeside53; 01-17-2016, 12:43 PM.

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                      • #12
                        Smart & Brown model A lathes have a trip on the feedshaft, it's built into the apron and is intended to be used when cutting to a shoulder. The feedshaft apron gears are carried on a sliding frame, when the carriage stops, the sliding frame continues moving towards the headstock, actuates a cam and disengages the feed lever. The leadscrew is protected by a shear pin located in the drive gear boss. The shear pin is hardened steel with a reduced section in the middle. My current Taiwanese lathe uses brass pins in the drive bosses for both the feedshaft and the leadscrew so power feeding to a shoulder is not an option.

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                        • #13
                          To me, a shear pin is the way to go, but...

                          is this what you have in mind?



                          http://www.dynatect.com/mechanical-m...slipper-clutch

                          One can also make slip clutch using two bearing balls, two set screws, two compression springs, and a couple of pieces of round stock.

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                          • #14
                            Or you could steal the clutch from an electric screwdriver, you can even set the tripping point on those.

                            Igor

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                            • #15
                              Mike Burdick---thank you.--That is exactly what I meant. I have asked them for a quote.--Brian rupnow
                              Brian Rupnow

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