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  • Induction Bearing Heater Idea

    I searched this forum and PM for ideas on an induction bearing heaters and didn't find anything that supported or disproved my idea, so here goes.

    I'm in the process of rebuilding 1 of the 7 machine tools I recently purchased and needed to replace bearings in a 10 HP lathe drive motor. I've used the hot pan of oil, and a torch but for the past 30 years I've used a commercial induction bearing heater at work. But now that I'm retired I don't have access to the nice induction bearing heater from work so I decided to build one.

    As I searched for parts to build one I got to thinking of a faster cheaper way to build or buy an induction heater that would heat bearings fast and easy. Which led me to thinking about an induction cooking surface. I found nothing on the internet about using an induction cooking surface to heat bearings but knowing the basics of how induction heating works I figured it would work. Maybe not as fast or convenient as a commercial induction heater but work just the same.

    So I bought an induction cooking plate for $55 and put it to the test heating the bearings for the motor. WOW! I was very impressed with the results. The bearing ID is roughly 1.5" and the OD is roughly 3". The instructions say minimum pan size is 5" so I was concerned that a 3" bearing wouldn't heat up so I placed a 6" ring around it first and set the plate for 212 deg F. And in 2 minutes and 45 seconds the bearing was 192 deg F according to my IR gun, what a discovery. Next I took the ring away and heated one of the old bearings in the center of the plate at 212 deg F and had basically the same result 188 deg F in 2 minutes 45 sec.

    So if you're looking for an induction bearing heater that you can also cook lunch on get an induction hot plate, I think you'll be impressed.

    Ron








  • #2
    Great Idea!
    It would be interesting to see what was possible with a thin ceramic insulator under the item to be heated and an insulating cover,

    - Nick
    If you benefit from the Dunning-Kruger Effect you may not even know it ;-)

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    • #3
      The rule for induction heating this way is the surface has to be magnetic so introducing a ceramic insulator under the bearing would prevent the hot plate from turning on. Also, in my opinion an insulated cover isn't necessary, the heating take place very fast with this type of heater and in general you only need around 200 deg F or 150 to 160 deg F delta T.

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      • #4
        I had a regular induction heater for bearings, the type you stick the bearing on a magnetic core and at the end of the heating cycle, there was a small automatic demagnetizing cycle that insured that the bearing was not magnetized. You should check if the cooled bearing is not magnetic and attract magnetic debris.
        Helder Ferreira
        Setubal, Portugal

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        • #5
          What about smaller bearings. Maybe down to 1/2" ID.

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          • #6
            Hey, that's great Ron!! Thanks for sharing your find and 'research' Now if you could just get one to go to heat treat
            temps.......

            Pete
            1973 SB 10K .
            BenchMaster mill.

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            • #7
              Nice. Good idea. I'm going to get one!

              I use a typical convection microwave - with NO microwave! Works well (170F-450F) for bearings, baking paint and heat treat tempering. Often you need to heat the female part (like a housing) and in my case , almost always Almag castings. As mentioned above, induction doesn't help unless it's steel/iron etc.

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              • #8
                Yes great idea and I can vouch for the fact it works very well.
                I picked up a new induction "hot plate" two years ago on Ebay for $30 shipped. It was listed as having a blemish but all I could find was a small crack in a decorative molding.
                Very fast and the nice thing is you have the option of presetting the desired temp.
                Home, down in the valley behind the Red Angus
                Bad Decisions Make Good Stories​

                Location: British Columbia

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                • #9
                  Originally posted by nc5a View Post
                  The rule for induction heating this way is the surface has to be magnetic so introducing a ceramic insulator under the bearing would prevent the hot plate from turning on.
                  I did say thin, in my opinion magnetic sensing of the item to be heated and it's size could still work through a thin insulator.

                  Originally posted by nc5a View Post
                  Also, in my opinion an insulated cover isn't necessary, the heating take place very fast with this type of heater and in general you only need around 200 deg F or 150 to 160 deg F delta T.
                  For heating bearings no opinion is necessary as clearly demonstrated by the OP.
                  Achieving higher temperatures could expand the potential uses in the workshop considerably though,

                  - Nick
                  If you benefit from the Dunning-Kruger Effect you may not even know it ;-)

                  Comment


                  • #10
                    I would only add that a thin insulating ceramic layer would have no effect on the magnetic field. The coil is not at the immediate surface of the hot plate, so adding a little more would be fine, although the surface of the heating plate is not a great conductor of heat in the first place. There might be little to gain, especially at the low temperature's that you are using.

                    I use a medium frequency induction heater for bending and forging. The principles are the same, but different frequencies have different effects. My coils are wrapped in an insulating material. More trouble is often caused by having the heated material to close to the coil than farther away. I my applications, a coil has a ID of roughly twice the dia. of the stock being heated.
                    paul
                    ARS W9PCS

                    Esto Vigilans

                    Remember, just because you can doesn't mean you should...
                    but you may have to

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                    • #11
                      I get by with a $1 incandescent light bulb. I set the bearing right on the bulb. Probably takes a little longer than induction heating but I don't notice while I'm getting ready to drop the bearing on. In a few minutes, it's ready.

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                      • #12
                        Just out of curiosity, how does the induction heater know the temperature of the bearing? I'm impressed.
                        Lacking a decent thermal contact it would almost be forced to track the change in inductance from the change of the specific resistance of the target material due to temperature rise. But I doubt this would work outside of a lab environment and even then only if you don't move the target.
                        Or does it just assume the top surface is the same temperature as the bearing and accept the lack of accuracy? I'm confused as my induction heater has a glass surface but this material looks different.

                        Igor

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                        • #13
                          That ferrous only deal...... it seems not quite to be about ferrous, but a combination of things which ferrous material tends to combine nicely. Some cooktops can in fact use copper, or at least aluminum bottoms, but not quite as efficiently.

                          Ferrous has a combo of features.... It carries the magnetic flux, and limits the depth of conduction *at the induction frequency*, despite being a high resistivity material, which would normally deepen the skin depth.

                          The better conductivity of aluminum and copper still has enough skin depth that they do not heat as well at the typical operating frequency. Obviously not a problem for this application, as nearly all bearings are ferrous material.
                          Last edited by J Tiers; 01-13-2016, 09:10 PM.
                          1601

                          Keep eye on ball.
                          Hashim Khan

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                          • #14
                            Actuallu the material just needs to be a decent conductor of electricity. It acts like a shorted turn on a transformer. Induced current causes the heating.

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                            • #15
                              Ron, good idea !.

                              I have been using my "Demagnetizer " for years for heating bearings.
                              Its a large old commercial unit about 6 inch in Diameter with a 2 1/2 Hole and 2 1/2" thick
                              After 15 seconds, the bearing starts to get pretty warm

                              Rich
                              Green Bay, WI

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