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attaching small plastic gear to shaft

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  • attaching small plastic gear to shaft

    I'm making a power feed for my mini-mill and I have a set of small plastic (nylon, white) gears taken out of a large laser printer. They have a heavy tooth and are a matched set of three which I will use as an idler to engage/disegage the power feed from the hand wheel.

    diameters - 0.7" (2) and 0.98" (1-idler)
    bore - 0.235"
    thickness - 0.216"
    these are flat, no extended hub surface.

    I was thinking that to attach to a shaft or hub that a simple friction fit secured with s screw could back off the screw when driven in reverse. Since there's no hub and they are thin I can't really put a pin through them.

    Maybe knurl the shaft and press them on, but to tight and they could split under pressure.

    Any ideas on this? or lost cause since they don't have an extended hub or molded in metal hub.

    I do plan on making some metal gears eventually so these do not have to last a looong time. After I get the power feed working I'm finishing my dividing head so I can make some gears for this and other projects.

    Thanks, Kevin

  • #2
    Make a bushing with a bolt flange, with a second flange on the opposite side that the screws screw into.


    • #3
      What about glueing them on with JB weld?
      I have tools I don't even know I own...


      • #4
        The single most common failure on laser printer drive motors is for the nylon pinion gear that is presed on to the drive motor shaft to split at the hub.
        Free software for calculating bolt circles and similar: Click Here


        • #5
          I've done this with similar printer gears on my wire feed unit. Used same solution as Billh. Unit's on its third roll of wire and still going


          • #6
            I took off my pictures so this thread wouldn't be so long coming in,
            on someone elses post.

            [This message has been edited by dvk (edited 12-06-2004).]


            • #7
              Hello Brunneng,
              I don't think you need to go that route.
              The motor that "Seig" the manifacturer uses
              engages in a slot directly into the lead screw. I have their variable speed motor installed on my mini-mill and it works great.Also the lead screw nut is a heavy brass plate set in a pocket. You just loosen the set screws from the right side of the pocket with an allen wrench then connect up the motor and retighten the allen screws. This aligns everything and
              eliminates any binding problems. "Little Machine Shop" has the motors for about 87.00.The way the lead screw on the new mini-mills are allready slotted allows you
              to just use their motor without having to buy the lead screw kit they used to sell.
              You can install the whole setup in about 10 minutes.


              • #8
                Thanks guys.

                I've been looking at the seig power feed, but I already have everything needed to make one from other projects and surplus. I'm not worred about alignment issues. That I can deal with easily. I will be running an extension from the x-lead through a bearing to support the whole shaft. Once adjusted it'll have no problems. This is to uncouple the lead from the gear motor for manual control.

                dvk: I was thinking around the same thing, just smaller in as I believe my gears are smaller. I was thinking of drilling a hole(s) for a round pin or two on the shear line similar to a keyway for slippage and follow up with a clamping screw axialy on the end for capture.

                Evan: one of the first gears I'm making is to replace a plastic gear on an older projector that exploded from internal pressure from the metal hub.


                • #9
                  I have never been able to figure out why the various manufacturers use nylon pinions on drive motors. It is the point of first failure, always. The additional cost for a metal pinion is probably ten cents. I have a Xerox laser printer that failed after only 6000 pages printed. The pinion on the main drive motor split. They won't sell just the 2 cent pinion gear to press on the motor shaft. No, you have to buy a complete motor drive assembly that costs more than the printer. This always torqued me bad when I worked for the company. Idiots.
                  Free software for calculating bolt circles and similar: Click Here


                  • #10
                    Hi Again,
                    Are you aware that with the "Seig" motor
                    you can crank manualy without disconnecting anything and because its variable can set to whatever speed you wish.


                    • #11
                      <font face="Verdana, Arial" size="2">Originally posted by Evan:
                      I have never been able to figure out why the various manufacturers use nylon pinions on drive motors. ...This always torqued me bad when I worked for the company. Idiots.</font>
                      I share your frustration. Just about everyone in the manufacturing industry is doing this with consumer products. I suspect that, that's the only way to reduce the price point so that a laser printer sells for $199.


                      • #12
                        Technically I don't have to uncouple my power feed either. It would just add the resistance of the gear motor like the seig unit does.

                        Evan: and of course this particular gear that broke is buried just about as far into the unit as you can get. I had to take 60-70% of the projector apart to get to it. It has a companion gear located above it that is fed from the same worm. I'm going to replace both while I have it open just to be safe.