One-sentence answer: The main enemy of power tools is dust, not water. Sealing failure at the mating face of the two housing halves, the switch cavity and the bearing cavity allows dust to enter the bearings and contacts, causing seizure and burnout. Using the CTS Sentinel A28 differential pressure leak detector to compare a master part with the part under test enables stable low-pressure judgment on plastic housings, making it suitable for 100% inspection on high-volume power tool production lines.
Drills and angle grinders are used on concrete, wood and metalworking sites where airborne dust concentration is high. The sealing goal is to stop particles from entering the bearing cavity and switch cavity, so the testing approach is not entirely the same as for waterproof parts.
There is usually no seal ring between the left and right housing halves; instead, contact is achieved through the fit accuracy of the mating face and screw torque. Missing screws, insufficient torque or flash on the mating face all create dust paths.
The bearing seats and gearbox generally need to keep grease from leaking out while preventing dust from entering, so the sealing condition of the two cavities must be judged separately.
Motor cooling requires an air inlet and outlet path, and the switch lever requires motion clearance. These locations must be plugged as defined during testing; otherwise it is impossible to distinguish designed paths from real defects.
Sealing locations:
Consequences of leakage: dust enters the bearings, accelerating raceway wear and increasing operating noise and temperature rise, eventually leading to seizure; dust entering the switch contacts causes poor contact or even short-circuit burnout; gearbox grease leakage leads to dry friction of the gears and a sharp drop in service life.
Power tool housings are small-volume, very high-volume, plastic mating workpieces, which places low-cost and high-cycle-rate demands on testing:
Because their main risk comes from dust ingress. Once the mating face and openings of the two housing halves fit poorly, dust will continuously enter the bearing cavity and switch cavity, causing wear, seizure and electrical faults. Air tightness testing uses gas as an equivalent substitute for the dust ingress path, allowing defects in the sealing of the mating face and openings to be screened out at the factory.
Handle it according to the sealing definition in the product design. If the grille is a path that is allowed to ventilate, it must be plugged as defined during testing so that only the sealing of the rest of the housing is evaluated; if there is a filter or labyrinth structure inside the grille that performs the sealing function, it should be treated as part of the test object. The specific judgment is based on the product drawing and fixed in the test program.
The two are complementary but not interchangeable. Air tightness testing reflects the sealing condition of the housing at the factory and belongs to production line interception; drop and impact testing verifies whether the product can still maintain sealing after impact and belongs to type verification. Tools in users' hands will inevitably be bumped, but on the production line only air tightness testing can hold the factory baseline.
The core of sealing testing for power tool housings is to hold the line against dust ingress paths under low-pressure, low-cost conditions. The CTS Sentinel A28 uses differential pressure comparison to support stable low-pressure judgment on plastic housings, and with clamping fixtures and 32 test programs it is suitable for high-volume mixed-line 100% inspection and traceability of tools such as drills and angle grinders.
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