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Someone donated an old microwave to our church office. The plastic frame of the turntable guide became distorted after many years. The white rollers continually came off of the ends of their axles. That caused the turntable to stop and to tilt.

We did not want to spend around $20 for a new turntable guide (even if we could find one the size we would need), plus still more dollars for shipping and handling.

Step 1: Measure Your Microwave's Bottom

You will need to know the outer diameter of the circle scribed by the rollers as the turntable revolves. In this Instructable I usually refer to the plastic rollers as white. Here one is shown in cross section as pale yellow for the sake of distinguishing the roller from other items in the graphic. The bottom of the microwave has rises and falls stamped into the metal, as you see here. When you decide on inner and outer diameters for the ring that will hold the plastic rollers, you will need to evaluate how much space you have so the ring does not bind unduly between the microwave bottom and the glass turntable. A cross section of the fiberboard ring is shown here in a copper color. The turntable drive is at the center of the fiberboard ring and the turntable. It is not always easy to get a clear view for measuring when peering into the microwave.

Step 2: Cut a Circle From 1/8 Inch Fiberboard

On our microwave the circle scribed by the rollers is 10 5/8 inch at its outer diameter. I cut a disc from the fiberboard 11 1/2 inches in diameter. Mark the center of the disc as precisely as possible. Lay out three lines radiating from the center spaced 120 degrees from each other. I scribed another circle on the disc 10 5/8 inches in diameter (the outer diameter of the roller track). I scribed yet another circle inside this circle just a little smaller. It was smaller by the thickness of the white plastic rollers plus just a tiny bit of "wiggle room."

I also cut a circle 8 3/4 inches out of the center of the disc to leave ring as shown in the graphic.

Step 3: Mark Holes for the Rollers

Mark the size of rectangular holes needed for the plastic rollers to fit inside those holes when the rollers rest on their edges as they did in the old turntable guide. These holes are on the 120 degree radial lines. Drill two holes to remove most of the material needed to make the rectangular openings. See the rectangle with the two holes at the left of the graphic.

Step 4: Clear the Holes With a File

Use a small file to clear the rest of the material from the rectangular holes. The plastic rollers should slide through the holes comfortably without a lot of extra play.

Step 5: Keeping the Rollers Vertical in Their Holes

The turntable guide needs to be lifted off of the bottom of the microwave a bit. It also needs a larger face to act against the side of the rollers so they stay vertical. Cut some rectangles from scrap fiberboard and glue them as shown. One will be above the ring you made and one will be below it. This may seem a little primitive, but it works.

Step 6: Install and Check

Put your new turntable guide into your microwave and test it. It should not hang up, but should work smoothly just like the old one did before it failed. Although viewed through the speckled glass, you can see the rollers and how they are held vertical by the scrap pieces glued in place.

Step 7: A Failed First Attempt

Parts of a microwave turntable need to be strong enough and yet should not be made of metal. My first attempt was to use a ring of 3/8 inch plywood with six holes for glass marbles. The marbles would act like ball bearings in a lazy Susan. Note the side profile at the right of the graphic.

This attempt failed because glass marbles are not perfectly round, even though they may appear that way. The turntable frequently hung up.

Step 8: A Partially Successful Second Attempt

For the second attempt I chose to cut down the 3/8 inch plywood ring I made for the marbles. I used nylon screws from the hardware store to hold the plastic rollers in place and to act as axles.

This worked fine for heating a cup of tea. But, if the microwave ran five or ten minutes, the nylon screws absorbed enough of the radiation and turned it to heat that the nylon melted. The plastic rollers were still fine, but the nylon melting created a useless turntable. In the photo you can see how the nylon screw melted and caused burn marks on the wood. Also shown is a new nylon screw.

Step 9: What I Would Like to Try

Everyone knows you should not have metal, like a spoon or aluminum foil, in a microwave while it is in use. The metal creates a lightning storm as charges generated in the metal by the radiation try to get to an electrical ground in the metal frame.

True as all of that is, I would like to try a ring made of steel with axles welded to the ring. The ends of the axles would be threaded and a nut would keep the plastic rollers from coming off of the end of the axle. There should be no lightning storm in the microwave, if the metal ring is electrically grounded to the metal frame of the microwave. See the smaller drawing to the lower left of the ring. A piece of light spring steel would be attached to the metal bottom of the microwave with a pop rivet. The spring steel would gently ride on the bottom of the metal ring. I have not tested it, but it should work.
I still haven't got round to replacing out microwaves turntable, I just balance plates on the gear, which is good for anything other than zapping a dinner that involves many things... I'd test that theory in an old microwave before using it, something doesn't seem to add up there, not sure why but it just seems a bit odd, a couple of motor brushes grounded to the frame touching the metal piece would keep contact well enough and wouldn't be high maintenance at such low RPMs.
Hmmm, seems to be a common problem... I also enjoy trying to balance my meals before nuking 'em. I was thinking along the lines of just epoxying the glass plate to the gear mech. But I have held back on that idea as I am thinking there is most probably a reason you shouldn't put epoxy in a microwave... Well it's may be fine, but still.
Personally, I do not think the center spindle that spins the glass has enough support to keep the glass level and keep it from dragging at the edges without rollers out around the edges, even if you could get a good glue joint to the spindle. What I did is really pretty easy and works very well, and it is quite simple to make. The fly in the ointment would be that you no longer have the little white rollers that came with your original turntable guide. Maybe you could find an old turntable guide with rollers in a junked microwave.
I would probably have been tempted to balance things on the drive gear or just put a rectangular piece of plywood in the bottom and let it be. But, there are several women in the office. Women seem to want certain things to work as original, regardless. I will probably never get around to testing my theory about stopping the lightning storms with a metal object inside a microwave by grounding it to the frame. Maybe a reader of this Instructable will test it and report back for all of us.
If there's a microwave being replaced any time soon I'm happy to try it out, I want my mother to give up on her stainless one, it looks good and is missing the plate but the second wall of steel would make me more comfortable with experimentations, also it's 900W so it'd have good components. We did have two industrial microwaves come with a house that used to be a B&B, sadly they were skipped, you could put anything in them and they'd continue on working, I once managed to get the superheated water experiment to work with one, it's mad...

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Bio: I miss the days when magazines like Popular Mechanics had all sorts of DIY projects for making and repairing just about everything. I am enjoying ... More »
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