The metal detector in our Zircon stud finder is useless for finding individual nails and staples in old furniture.
![shotgun lathe and plaster wall penetration test shotgun lathe and plaster wall penetration test](https://www.diydoctor.org.uk/images/repairinglathandplaster.jpg)
I salvage wood from old furniture for my woodworking. Stud finder metal detectors are not precision tools. It is better than nothing and not that reliable in our house, but it was the best we could find. Our Zircon stud finder has a regular and "deep" scan mode, a metal detector, and electric current detector. All too often I predrill through the plaster and hit air instead of a stud. I use a combination of the top of the line Zircon stud finder, neodymium (super-) magnets that I harvested from old disk drives, and the back of a spoon for the "listen test." I prefer spoons to light hammers for the listen test. We have a 1950s house with plaster walls. Any ideas on how to locate studs and crossbeams (width) in lathe and plaster walls? I have to be careful re dust since the old paint may be lead based. The resistance to the 1/16" drill bit was mildly firm for the first 1/2" or so into the wall, then there was no resistance for about 1/4" or so, then the mild resistance returned suggesting maybe I hit some lathe.
![shotgun lathe and plaster wall penetration test shotgun lathe and plaster wall penetration test](https://1.bp.blogspot.com/-oFzoLYjaGgc/VIwUKmoQcZI/AAAAAAAAJS0/lfdAwpXHH7w/s1600/lath%2Band%2Bplaster.jpg)
My stud finder was inconsistent in identifying stud locations and did not appear to work, and my friend thought his stud finder worked in identifying stud locations, but when I tested the identified marked locations on the wall by drilling a 1/16" diameter hole (about 1.5" into the wall), the drill bit resistance was the same at the stud finders marked locations and everywhere in-between the marked locations, meaning neither stud finder appeared to work on the old lathe and plaster walls. I used my stud finder, and separately a friend used his (a different brand, different time) to try to locate studs and crossbeams over an entrance-way from the front room to the dining room in an old 1920's era house.