This is something that comes up quite a bit in the metal detecting business with newcomers asking. How deep will it detect? That depends on a few things and we will try to set the record straight on this issue. First off pretty much all metal detectors will detect coin sized objects down to a depth of 5-6”. With the way the ground moves, frost, erosion, construction fill etc. 99% of all your finds will be at the 5-6” level.  Now don't let that discourage you as it does not sound like your going to really going to hit buried treasure at 5”. But thats not true. Coins and jewellery as well as relics will easily be found at this level. Coins from the 1700's and 1800's, victorian jewellery and other objects are found here most of the time. So when you ask how deep will it go. You really need to ask how well will the machine see down that deep?
What that means is, some metals and minerals in the ground mask or block the way a metal detector sees a target. Iron objects and rusty old nails give off a very large signal. As do aluminum and pop cans. This can mask the good targets and block your machine from doing the job.  Targets thats are of value or interest to most people are small and coin sized like gold rings. A good metal detector will handle this situation sometimes not perfect. But the brands from well known manufacturers have been designed to look around or ignore these obsticles and not loose depth or performance.
So when your looking at a metal detector don't ask how deep will it go? But rather how well will it perform in the type of hunting I want to do. Parks, beaches, fresh or salt water environments all play a part in how the machine sees down into the ground. Digging trash is interesting at first. But once you have dug your 100th nail or bottle cap, believe me it will dampen your treasure hunting spirit pretty fast.
So stick with proven performers and enjoy the metal detecting hobby. There is a lot of treasure still buried out there.
Jeff Peacock
Middlesex Detector Sales