I am installing a ceiling fan, my ceiling junction box is metal and I don't understand how this is secured? It would be 1950's wiring. Can I simply install the new ceiling Fan with no worries that the metal box can hold it? I can't tell how the box is secured, it looks as if it has a metal bolt running through the middle of the junction box but is this secrued to the beam? Also, the junction box has a little play in the ceiling, meaning I can move it around a bit. This worries me that the only thing holding it is wiring and plaster??

What you probably have is a box that is attached to a bar, see the attachment for a photo of a typical outlet box with a bar hanger. The box is connected to a expanding bar, which is attached to both sides of the two joists. This is usually used to locate a box in between two joists, typically when the center of the room falls between two joists.

The bar itself has some flex or give to it, which is the movement you are seeing when you press against the interior of the box.

All boxes have weight limitations, this box I show you is made by Raco,part number 325. It has a UL listing of 50 pounds, Raco will only allow 15 pounds.

Now any box to support a paddle fan must be listed as such. The box you have that was installed in the 50's I am sure is not.

You can remove the existing outlet box form the bar hanger, and get a 4 in round box rated for paddle fans and install it onto the bar.

The "fan box" is arranged so the two 8-32 screws are not the only attachment to the box, long bolts will go through the box up into the top of the box, some threaded, some welded. In any case, the fan will not rely solely on the two small screws.

Hope this helps. Get back with any other questions you may have

I am installing a ceiling fan, my ceiling junction box is metal and I don't understand how this is secured? It would be 1950's wiring. Can I simply install the new ceiling Fan with no worries that the metal box can hold it? I can't tell how the box is secured, it looks as if it has a metal bolt running through the middle of the junction box but is this secrued to the beam? Also, the junction box has a little play in the ceiling, meaning I can move it around a bit. This worries me that the only thing holding it is wiring and plaster????

If the wiring is that old the ceiling box may be attached to a board "scabbed" across the joists. They make heavy duty replacements called saf-t-bar or something like that just in case you want to replace it. They have sharp points on each end and when you turn the bar with a wrench it expands forcing the points in to the joists. I've used them in old houses and they work great.. they aren't cheap but you could just about hang from one when they're installed... no problem holding a ceiling fan.