Technique in the field
Metal Detecting Sweep Technique: Coil Height, Speed and Overlap
Quick answer
Keep the coil level and within about an inch of the ground across the whole arc, sweep at roughly one to two seconds per pass, and overlap each pass by about half a coil width while stepping forward less than one coil length. Lifting the coil at the ends of the arc is the most common depth loss in the hobby.
Sweep technique is the cheapest upgrade available. It costs nothing, it applies to every machine ever made, and the two most common faults both remove depth in exactly the region where the interesting targets live. Neither fault feels like a mistake while you are making it, which is why people carry them for years.
The first is the arc. An arm swung from the shoulder describes a curve, so unless you consciously correct, the coil is on the ground in the middle of the sweep and several inches up at each end. The second is speed, which interacts with recovery speed and with the machine ability to process two targets in succession. Both are covered below, along with the coverage arithmetic that decides whether a site was actually hunted or merely walked over. If your coil is wobbling rather than your arm, start with the maintenance routine instead.
Top pick
Detecting Harness and Swing Support
Eight adjustment points and a bungee that takes the swing weight off the forearm, which is what makes a level arc sustainable across a full day rather than a first hour.
Price was accurate when this page was compiled and changes often.
On this page
How high should the coil be, and why does it matter so much?
As close to the ground as the vegetation allows, within about an inch, and level across the whole arc. The field from a coil weakens quickly with distance, so an inch of unnecessary height at the end of a sweep is not a small percentage loss, it is the difference between hearing a deep coin and not knowing it was there. The practical test is simple: ask somebody to watch you swing from the side, or film thirty seconds on a phone propped on the finds pouch. Almost everybody is shocked by the lift at the ends.
The fix is to swing from the shoulder and elbow together rather than pivoting on the shoulder alone, and to shorten the arc until it is level. A narrower level sweep beats a wide curved one every time. On uneven stubble or tussocky pasture, accept a little more height rather than banging the coil, because a coil hit hard enough to bounce also falses, and because coil housings are not cheap.
What do the common faults actually cost?
None of these are subtle once you look for them, and all of them are free to fix. Work down the table and be honest about which two are yours.
Lifting the coil at the ends of the arc and stepping forward a full coil length between passes are the two faults that remove the most ground from a hunt, and both cost nothing to correct.
| Fault | What it looks like | What it costs | The fix |
|---|---|---|---|
| Arcing | Coil on the ground in the middle, inches up at each end | Most of your depth across two thirds of the sweep | Swing from shoulder and elbow, shorten the arc until it is level |
| Sweeping too fast | A brisk scrub, usually when tired or bored | Deep and marginal targets, and target separation in trash | One to two seconds per pass, timed against your own footsteps |
| Sweeping too slowly | Almost a pause at each end | Very little depth, but a great deal of ground per hour | Only worth it on a known hot patch, not as a default |
| Stepping too far forward | A full coil length or more between passes | Unhunted lanes between passes, invisible on the day | Step half a coil width or less, and mark your lane |
| Insufficient overlap | Passes that touch rather than overlap | Targets under the weak outer edge of the coil field | Overlap by about half a coil width on every pass |
| Hunting one direction only | Lanes run north to south and never across | Targets that only speak along one orientation | Grid the site a second time at right angles |
| Coil not level side to side | Consistently tilted, usually from a loose lower shaft | Depth, plus falsing that gets blamed on the machine | Tighten the clamp, check for play, replace a worn shaft |
Every one of these is easier to see than to feel, so film yourself for thirty seconds. It is the fastest technique correction available and it costs nothing.
How fast should you actually sweep?
Roughly one to two seconds per pass for most coin and relic hunting, which is far slower than it feels natural to walk. The constraint is the machine recovery speed, meaning how quickly it can report one target and be ready for the next. On a site with a nail every foot, a fast sweep runs two targets together and you hear one confused signal instead of a nail and a coin. Slowing down is free separation.
There are exceptions. On open ploughed ground with almost no trash, a slightly faster sweep with a large coil covers more acres per hour and costs little, which is the trade the coil coverage calculator puts numbers on. On a dense old house lot with a small coil, slow down again. Speed is a site decision rather than a habit, and the mistake is having one speed for everything.
How do you make sure a site is actually covered?
Grid it. Pick a lane width you can hold, work it in straight lines with an overlap of about half a coil width, and mark the edges with something visible rather than trusting your memory of where you stopped. Then hunt it again at ninety degrees to the first pass, because target orientation matters: a coin standing on edge can be near silent along one axis and obvious along the other.
The search grid planner turns a field size into lanes and a walking distance, and the numbers are usually sobering. A small paddock properly covered at a sensible sweep speed is a full day, not an hour, which is why people who hunt one permission carefully out-find people who skim six. The same arithmetic is why site research matters more than mileage.
How do you keep good technique when you are tired?
Support the weight. Technique collapses in the fourth hour because the forearm is done, and the arc gets wider and higher exactly when you have reached the interesting part of the site. A LimbSaver Comfort-Tech Metal Detector Sling at $20.23 spreads the load across the upper body, and a full Detecting Harness and Swing Support with a bungee takes the static weight off the arm altogether, which is the single biggest comfort upgrade for a heavier machine.
Beyond that, alternate arms if your machine allows it, take the pack off every hour, and use NoCry Professional Gel Knee Pads so that kneeling for every recovery does not become the thing that ends the day. Detecting elbow is a genuine repetitive strain injury and it comes from hours of unsupported swing weight rather than from any single bad swing. The weight comparison is worth reading before you buy anything heavy.
Sources
- Manufacturer instruction manuals, sweep speed and coil height sections
- Published coil specifications and recovery speed settings from Minelab and Nokta
- Manufacturer product listings for the harness, sling and knee pads named
Frequently asked questions
How close to the ground should the coil be?
Within about an inch, and level across the entire arc rather than just in the middle. The field weakens rapidly with distance, so height at the ends of the sweep removes depth exactly where you are least likely to notice. On rough stubble accept slightly more height rather than striking the coil, because impacts both false and damage the housing.
How much should each sweep overlap the last?
About half a coil width, with a forward step shorter than one coil length. The field under a coil is weakest at the outer edge, so passes that merely touch leave a strip of ground covered only by the weakest part of the field. Overlapping feels slow and is the difference between hunting a site and walking over it.
Does sweeping faster find more ground per hour?
It covers more ground and finds less in it. Above roughly two feet per second most machines start to run adjacent targets together, so on trashy ground you lose the good target beside the nail. On clean open ground with a large coil a faster sweep is defensible. Treat speed as a site decision rather than a habit.
Should I hunt a site in two directions?
Yes, wherever the site justifies a second pass. A target lying on edge or at an awkward angle can respond clearly along one axis and be almost silent along the other. Gridding at right angles to your first pass is the standard way experienced detectorists get second and third finds out of ground they have already worked.
Why does my machine false at the ends of my swing?
Most often because the coil is being lifted, tilted or knocked at the end of the arc, or because the lower shaft has play in it and the coil moves independently of the rod. Check the clamp and the shaft for movement first, then watch the arc itself. A cable tapping the shaft at one specific angle produces the same symptom.
Researched, not professional advice. This page is compiled from published specifications, manuals and owner-review consensus, not hands-on testing. Target ID numbers, depth figures and settings vary with soil chemistry, moisture, target size, depth, orientation and firmware version, so treat every figure here as a starting point and verify it against your own machine's manual and your own ground. As an Amazon Associate we earn from qualifying purchases.