Research scope: We checked Milwaukee’s official 2291-20 product record and operator manual. We did not test detection depth, false readings or calibration.

The product is no longer current

The Milwaukee product most often meant by “Milwaukee stud finder” is the 2291-20 M12 Sub-Scanner detection tool. Milwaukee marks it no longer available. It was a professional scanner designed to locate wood and metal studs behind non-metallic wall materials, distinguish ferrous from non-ferrous metal and measure rebar location/depth in concrete.

That is materially different from a simple alkaline center-finding stud sensor. A used unit may still work, but its former list of capabilities does not prove present calibration, battery health or parts support.

Why scanners miss studs

Wall scanners infer changes below a surface. Plaster and lath, foil insulation, wire mesh, wet material, tile, multiple layers, irregular stud spacing and nearby metal can produce ambiguous readings. Follow the model’s calibration routine on the actual surface, scan in both directions and repeat at more than one height.

No consumer scanner should be treated as permission to drill. Cross-check with layout, visible fasteners, outlets, attic/basement access and a small verification method appropriate to the finish. Shut off and verify circuits when work could reach wiring. Water, gas and refrigerant lines can be present even when the display does not identify them.

Buying a used 2291-20

Check the display, wheels, housing, battery contacts and calibration behavior. Confirm whether the sale includes a compatible M12 battery and charger. Read the manual and locate authorized service before paying a premium. Milwaukee’s old depth claims were application-specific and should not be generalized to every wall assembly.

For routine drywall stud finding, a current, supported dedicated sensor may be cheaper and easier. For concrete or multi-material scanning, hire or use an instrument designed and supported for that substrate, then confirm the result through other evidence.

Verdict

The 2291-20 is an interesting used professional detector, but it is not a current Milwaukee recommendation. Buy only when its exact capabilities are needed, condition can be checked and lack of current availability is reflected in the price.

Use Milwaukee’s archived product record and operator manual to identify the tool and its limits.