And remember that meat is flammable if you heat it (enough), so you shouldn't attempt to cook meat in a microwave... (?).

As long as the material used is a non-conductor of electricity, it will not get hot in a microwave, so any adhesive that doesn't conduct electricity after it's properly cured is unlikely to get hot enough to cause chemical breakdown. The "spider" itself is most likely a thermoplastic. Neither the spider nor the glass plate should get heated except by conduction from whatever is heated on top of the plate (unless you've spilled conductive liquids into the roller track, which is fairly common).

In any spider I've seen, however, it's difficult to see how yours could have broken in any way that provides sufficient bonding surface area for any kind of successful glue joint. You might get it temporarily stuck together, but you can expect it to come apart again soon after.

Best advice is to get a new spider. You may find one available from the microwave maker, or from a local appliance repair shop.

You might also find one in a microwave at a yard sale. Microwaves don't sell well at yard sales in my area, so you probably can get one that's cheap but has a good spider. Salvage the spider, check out which of your two microwaves works best, and junk the other.

(If someday you junk a microwave that has a good spider, you might save the spider - and the glass tray - for your next yard sale, since they do comeapart fairly often, so you can probably sell a good spider for about what a whole microwave would bring.)

If you want to do a little "research" you might be able to find a light duty "all plastic" lazy-susan to support the glass and allow it to rotate, but the design of your microwave will determine whether you will be able to "connect the rotation." Some microwaves turn the spider, and some engage a "knob" on the glass. Either way, you may have to devise an appropriate "connection."

If the spider actually is a thermoplastic, a low-watt soldering iron with a "virgin" (never used for soldering) tip might allow you to make a weld in the plastic, or the acetone (or acetone glue) might work; but the welding is a "learned skill" and requires some knowledge and judgement - and isn't much more likely to be permanent than a bad glue patch.

John