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Gears for Stepper — Parallax Forums

Gears for Stepper

fltcmdrfltcmdr Posts: 14
edited 2010-08-21 20:09 in Robotics
Has anyone worked with the Parallax stepper motor. Specifically where to get gears to mesh with the metal one on the stepper??
MC

Comments

  • dandreaedandreae Posts: 1,375
    edited 2010-08-17 06:41
    The diameter of the shaft is .116"

    The diameter of the gear is .369"

    The depth of the gear is .316

    There are 17 splines on the gear. You can check with McMaster-Carr at:

    www.mcmaster.com

    Dave
  • ercoerco Posts: 20,256
    edited 2010-08-17 10:16
    @Dave: What's the diametral pitch on the motor pinion? That's the critical info missing. And in the photo on the Paralllax website, I count 16 teeth, not 17. Can you double check that?

    @fltcmdr: That brass gear on the motor can be easily removed and you can install any other pinion as well.
  • John R.John R. Posts: 1,376
    edited 2010-08-17 10:25
    erco wrote: »
    @Dave: What's the diametral pitch on the motor pinion? That's the critical info missing.

    and the pitch angle... (less critical, but important)
  • ercoerco Posts: 20,256
    edited 2010-08-17 11:11
    I bet you mean pressure angle... likely 14.5 degrees. :)

    http://en.wikipedia.org/wiki/Pressure_angle
  • John R.John R. Posts: 1,376
    edited 2010-08-17 11:33
    Yup, that's what I meant. If unkown, 14.5 should be safe to use...
  • Martin_HMartin_H Posts: 4,051
    edited 2010-08-17 17:02
    Erco, I have some steppers and DC motors I salvaged out of a printer. I'd like to swap the belt gear on the DC motor over to the stepper, but I wasn't sure how to take the gears off.

    You mentioned they are easy to take off. I don't see a set screw, so what's the trick? Are they just held on with a lot of friction?
  • ercoerco Posts: 20,256
    edited 2010-08-17 17:11
    Yes, they are usually a press fit, especially brass gears on a splined steel shaft. It's easy to mangle them off, you can "carefully" crush the brass gear off in a vise. Brass is softer than steel, so it will shear off and leave the steel motor shaft in good shape. To preserve the gear you want to remove is a bit trickier, you need to support the gear edges (2 plates atop a vise, straddling the motor shaft works) and tap on the motor shaft with a center punch to drive it out.
  • Martin_HMartin_H Posts: 4,051
    edited 2010-08-17 17:15
    Thanks! I figured that might be the case, but I was afraid to try it. Now I can mangle one of the gears with courage.
  • fltcmdrfltcmdr Posts: 14
    edited 2010-08-17 17:18
    Thanks for the info on the gears. Its a great help. Micromark sells a gear puller that should easily remove the gear intact. I have one on order in case I cant find suitable gears for my turrets. Again thanks. and there are 17 teeth
    MC
  • fltcmdrfltcmdr Posts: 14
    edited 2010-08-17 18:02
    OK I went to the Mcmaster site and they said the pitch is the no. of teeth divided by the pitch diameter. Which by thier drawing looked to be about halfway up the tooth. using the gear diameter and depth you gave me I estimated it to be about .342. that equates to an estimated pitch of about 49. None of their gears are even close to 49. 32 is the largest.
    Am I doing something wrong or are their gears just not suitable???
    MC
  • ercoerco Posts: 20,256
    edited 2010-08-17 19:21
    48 pitch is standard for US gears, that's darn close and probably it! Metric is also a possibility, which is sort of the reciprocal of DP. DP is teeth per inch of diameter, whereas module is the metric width of a single tooth.
  • fltcmdrfltcmdr Posts: 14
    edited 2010-08-18 00:15
    Uh ok well ya lost me on that. It says its made in china but it dusnt mean they didnt use a US gear. Plastruct sells a gearset that just mite fit the shaft. but Id rather buy steel for the turrets They will be tougher.
  • fltcmdrfltcmdr Posts: 14
    edited 2010-08-18 01:07
    Most of the gears that I have looked at are 20degree. I dont know if they would work or not because no serious specifications were supplied with the stepper. Obviously it meshes with "something" but it slows the project down considerably trying to figure out what. I figured this would already be worked out by now.
    MC
  • fltcmdrfltcmdr Posts: 14
    edited 2010-08-18 02:23
    The item number for the puller from micromark is 82392. on sale for about 7 bucks
    MC
  • kelvin jameskelvin james Posts: 531
    edited 2010-08-21 20:09
    I would think a 20 degree pressure angle to be pretty well standard for a commercial brass pinion gear. Check the pitch diameter for meshing to another gear.
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