hvac
There is a metal plate on the top of my basement's celing.
It is attached to the HVAC ducts, but doesn't appear to be a duct itself.
I'm interested in using the stud it is attached to hang an LED strip light that requires stud access.
Can I drill a pilot hole through the sheet metal to attach it to the joist? What is the purpose of the sheet metal?
If you're not too concerned about aesthetics, you can use some flexible duct (or dryer duct) and a couple boots.
Use some foil HVAC tape to connect one boot to the duct on the ceiling, and then put the other boot on the ground, and use foil tape to connect the boots to the flex duct.
You can get boots that are straight, 45, 90 degrees, and horizontal or vertical, and many sizes -- the box stores all have lots to choose from.
You can also stick a grill on the bottom, just to make it look a very slight amount nicer.
A wooden beam like used for a joist will typically face bending loads. You'll have a great deal of compressive stress on the top of the beam and a great deal of tension stress on the bottom beam. The center serves primarily to keep the top and bottom of the beam aligned so they act as a single beam, and is under shear stress parallel to the grain.
As such, a hole like you pictured (in the center vertically and horizontally) will probably be fine.
I'd be leery of doing that closer to the end of the joist because if the shorter remaining center portion of the beam (hole to end of joist) was too short it could fail in shear and the top and bottom of the 2x10 would act as independent 4" beams (weak).
I'm not a structural or mechanical engineer, who would obviously be more qualified to determine this, but I am an engineer.
Best Answer
This appears that they used the channel between studs as a return air duct. Look at the duct that attaches to it and see if it is also a return air duct or if it goes to the return side of the air handler.
That said, drilling a small hole to hang something should be fine. Make sure you drill as close to the center of the stud as you can - you don't want a random hole in the return air duct if you can avoid it. If you have some kind of hole-drilling accident, a piece of aluminum duct tape or duct sealant should fix it.