conduit
I have a junction box with a knockout that is 1-5/8" diameter. (it was homebrewed, possibly in 1929).
Would this be suggestive of a particular type of conduit? It will definitely be metal conduit.
Related, I need to make a sharp turn out of that, turning 90 degrees in about 5". Is there a way to do that? I do have access to one side, but it's rather awkward so I'd like to avoid a conduit body.
Cut open the drywall. You can then use a piece of plywood to cover the hole so that it's easier to remove in the future.
Sounds like too much work. First step, make sure they are GFCI protected. If you don't know if they are GFCI protected, you can get a GFCI outlet tested from the hardware store. And while you're there, get outdoor box covers. Then you can just replace the face plates with the outdoor box covers. MUCH easier than removing the outlets.
You don't need conduit. Get an "old work" electrical box. Cut a hole BELOW your breaker panel. Run the wire from that hole straight up through a knock-out in the bottom of the breaker box. Then you can push the wire through the top of the "old work" electrical box and mount the box in the wall. See, no conduit needed!
Based on response to my first answer:
Hooray!
Turn off the breaker. Remove the outlets and install wire nuts on all of the wires. Install blank faces plates.
OK, you still don't need conduit. Just drill a hole through the top plate of the wall. You can then run the cable up the inside of the wall, through the hole, and then down to your breaker panel with all of the other wires.
You want a PVC-to-threads adapter as depicted below (presumably 3/4" to match the size of the knockouts on your box, with a 1" to 3/4" PVC reducer used to adapt the LB's 1" to the adapter's 3/4").
You then use PVC from the LB to the adapter/reducer pair, and a locknut to hold the adapter to the box.
Best Answer
1-1/4" pipe (which are also IMC/RMC sizes) are 1.660 OD which is pretty close to 1.625. The thread start diameter on the narrow end of pipe threads is 1.557 so a nipple ought to get in the hole even if it's just that size. EMT fittings (on the threaded part) are normally threaded the same as the pipe/RMC/IMC size.
One of those weird pulling elbows is the only sharp turn I know of in conduit, other than using a conduit body, or a box.