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Technical Today’s science lesson bearing heater

Discussion in 'The Hokey Ass Message Board' started by Reidy, Jun 8, 2020.

  1. Reidy
    Joined: May 13, 2016
    Posts: 93


    Hello all, today I tried an experiment that most of you may already know about, but it was knew to me so I thought I would share. It involved heating a bearing up to close to 100C / 212F but not over to install on a shaft. It uses a microwave oven. I did not want to try this with the good one in the kitchen. Yes I am married. We had an old microwave at work that was either getting thrown out, or donated to science to study what happens to a six month old stew that has been reheated 40 times. It could be used as an industrial coating, but that is a different story.

    The process involves wrapping the bearing in a damp rag or paper towel and giving it a couple of minutes on high. It is that easy.

    Now for the science part. The microwave oven heats the water molecules and the heat is rapidly conducted to the bearing. As water turns to steam at 100C / 212F the rag will only get to 100C / 212F. Therefore the bearing can’t get any hotter. Most of us have been told bad things happen when we put metal in a microwave. You may ask why not this time. Essentially the damp rag creates a Faraday’s cage around the bearing. The simplest explanation of this is the water conducts the radiation around the outside of the metal and not through the metal, therefor no arcing and sparking. If you leave it long enough, all of the water will turn to steam and then arcing may/will start.

    So if you find a $5 microwave on Gumtree you can quickly heat a bearing for assembly.

    Steve from down under
    6-bangertim and skip65 like this.
  2. karl share
    Joined: Nov 5, 2015
    Posts: 103

    karl share

  3. mark460
    Joined: Jun 29, 2009
    Posts: 21


    I picked up a toaster oven from a DAV (Goodwill) type of place for less than $10.
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  4. GTS225
    Joined: Jul 2, 2006
    Posts: 1,168


    Plain, old, light bulb placed on the bore.
    Or you could get really lucky, like I did years ago, and get a real bearing heater at an auction for $7.50, because nobody else knew what it was. Even the auctioneer had to ask me.

  5. Vern H
    Joined: Jun 6, 2020
    Posts: 2

    Vern H

    The toaster oven works great, I’ve used one for years. Set heat at 250°F, never any higher it will affect the metallurgy of the bearing this according to all bearing manufacturers. As a millwright I’ve used these guidelines for years and it has always worked out. Use a 200°F and a 250°F temperature stick to check for accuracy. These are available at any professional welding supply store.

    Sent from my iPhone using The H.A.M.B. mobile app
    warbird1 and Truckdoctor Andy like this.
  6. Blues4U
    Joined: Oct 1, 2015
    Posts: 4,759

    from So Cal

    I can't imagine steaming a bearing is very good for it. Moisture and hot steel is a recipe for iron-oxide.
    iwanaflattie, saltracer219 and 302GMC like this.
  7. 19Fordy
    Joined: May 17, 2003
    Posts: 6,865


  8. goldmountain
    Joined: Jun 12, 2016
    Posts: 1,965


    How about the barbecue?
    olscrounger and Blues4U like this.
  9. williebill
    Joined: Mar 1, 2004
    Posts: 2,582


    At the shop, when we put fork bottom races on forks, we put them in any old cup with water, and microwave the hell out of them. I wait until they are boiling furiously, then remove and push on quickly. Never any arcing, and the 40 year old shop microwave keeps on microwaving.
  10. Lepus
    Joined: Nov 18, 2016
    Posts: 246


    You can also put the shaft in the freezer for a while before assembly. I do this for aluminum plugs in coolant channels in aluminum parts at work, (making scientific equipment) where I need a real tight fit, and would gall up both pieces trying to assemble them without the heating and cooling. It might help with bearings too.
    lothiandon1940 and tb33anda3rd like this.
  11. Onemansjunk
    Joined: Nov 30, 2008
    Posts: 167

    from Modesto,CA

    Going to give this a try ASAP. Thanks Reidy
  12. olscrounger
    Joined: Feb 23, 2008
    Posts: 3,900


    lots of good info. I had issues with bearing spacers on spindles. Put a bag of ice on the spindle and the bearing on the BBQ and checked with heat gun at 250--went on smoothly-done a few sets with no issues
    lothiandon1940 likes this.

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