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Help Removing A Plastic Washer from Corroded Steel Shaft

  1. Dec 30, 2016 #1
    I have a plastic slinger (hdpe, I believe) that is attached to a dishwasher motor shaft that I'm trying to disassemble so that I can replace it's bearings. The sling will twist independently of the shaft, but it won't come off. I've been thinking of hitting it with a penetrating catalyst (PB Blaster) or possibly some acid (maybe naval jelly, possibly a soak in a strong citric acid solution), but, if memory serves me correctly, both will do a lot of damage to plastic. I'm pretty sure, if I'm careful, I can keep whatever I'm using off the aluminum, but I have no idea how to de-rust/loosen this. Any ideas?


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  2. jcsd
  3. Dec 30, 2016 #2

    phinds

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    There are various forms of "liquid wrench" that I think are safe for plastic.
     
  4. Dec 31, 2016 #3

    rbelli1

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    The corrosion does not look too severe. Try sandpaper.

    BoB
     
  5. Dec 31, 2016 #4

    JBA

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    Strange as it sounds, a pour bit of Coke (soft drink) on the shaft and use an abrasive pad to remove rust.
     
  6. Jan 2, 2017 #5

    Baluncore

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    Remove loose rust from the shaft. Apply a lubricant such as soap, jelly or grease to the shaft.

    Heat the plastic with a hot air gun. Plastic will expand greatly and will soften so it will ride over bumps on the shaft. Then slide the slinger up the shaft.

    You should push a plastic tube along a shaft from the back end, it will expand radially when compressed axialy. You should not pull it from the leading end because the diameter will reduce and it will grip the shaft more tightly.
     
  7. Jan 2, 2017 #6

    JBA

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    All of the above is good advice; but, if your bushing is made of HDPE be very careful about heating it, because HDPE has a heat deflection point of only 180°F and a melting point of 250°F, so it is easy to overheat and deform or melt the edges of a part from this material with a heat gun.
     
  8. Jan 2, 2017 #7

    rbelli1

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    Good eye.

    I have used a polystyrene vessel semi-successfully with near boiling water (90+C?) but it had some deformation and the ability to hand bend. Polypropylene has so far been undamaged with the same abuse.

    http://www.matweb.com/reference/deflection-temperature.aspx

    Based on this chart it looks like HDPE would fare even worse under this condition.

    BoB
     
  9. Jan 2, 2017 #8

    Stephen Tashi

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    A "gear puller" is often used in auto mechanics when it involves only metal parts. You could use a puller if you find a way to safely distribute the stress from the puller over the plastic part. Try the suggestions in the previous post. If you can't get the plastic slinger off the shaft just by "fiddling" with it then you might have to resort to a puller. You may be able to temporarily hot-glue pieces of wood or metal to the face of the slinger to provide a way for the puller to grip the slinger and distribute the stress. Freezing things that have been hot glued usually releases the glue.

    Another similar situation from auto mechanics is the task of removing a wheel lug bolt from the rim of a wheel. An efficient way to do this use a vibrating impact tool like a air chisel with a blunt bit to hammer out the bolt. For some reason, the short strokes of an air chisel work better than smacking the bolt with sledge hammer. If you can temporarily attach the face of the slinger to some boards, you could try tapping on the end of the shaft to knock it out of the slinger or using some sort of vibrating tool to push the shaft out.
     
  10. Jan 2, 2017 #9

    rbelli1

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    Gently of you need to resort to this. You can shift things in the motor or damage bearing if to zealous.

    BoB
     
  11. Jan 2, 2017 #10

    Baluncore

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    I am sorry about suggesting a hot air gun when a hair drier would do the job equally well with HDPE. However, I would expect a more rigid, higher temperature plastic than HDPE in that application.

    It looks to me like two flat bladed screwdrivers between the slinger and the motor, one each side of the shaft, would be more than sufficient to slide that slinger along the shaft.

    Rust converter contains phosphoric acid. A molasses bath converts rust to lower volume compounds. Coke contains phosphoric acid and sugar, together they convert rust and teeth to have a lower volume.

    The pendulum “tuned mass damper” in the OP pictures with the hexagonal adjustable? head is interesting.

    It would be good to get some feedback from the OP.
     
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