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A clamp screw is an adjustable closure with a threaded cylinder and flared head. Many clamp screws have a similar appearance to a common bolt when they are detached from the clamp assembly. Clamp screws are often tightened by hand for fine adjustments to the tension of a clamp. The size of a clamp opening gradually decreases as the clamp screw is twisted farther into place. Screw clamps are commonly used to hold a part in place or regulate the flow rate through a hose.
The base of a clamp screw can leave a circular indentation on the surface it presses down onto. Clips and washers are often placed between the bottom of the clamp screw and any vulnerable surface to prevent direct contact. Protective hardware may be permanently welded to the end of clamping screws or simply slid into place prior to use. Small rubber pads can increase traction and provide a cushion against the pressure applied by clamp screws. Aggressively over-tightening a clamp screw may cause damage to the clamp and whatever it is holding, even if washers and pads are in place.
Hose clamp screws squeeze flexible hoses to constrict the flow of liquids and gases. The size of the passageway inside the hose reduces beneath the clamp as the base of the screw presses down. A properly applied screw clamp can effectively decrease or stop the flow coming from a hose without causing hose damage that could lead to a leak. Fully secured screw clamps may cause extreme pressure to build up in the section of the hose prior to the clamp.
Clamp screws used in automotive applications may require occasional tightening due to offset loosening caused by engine vibration. As with many threaded fasteners, clamp screws can be rattled loose by long periods of shaking. Adhesive products applied directly to the threads of a clamp screw can make its connection and position on the clamp more permanent. Permanently setting clamp screws with adhesives takes away the adjustable feature of the clamp and makes it difficult to remove without damage.
A needle clamp screw is commonly used to hold a sewing machine needle in place during use. The clamp screw is gently tightened onto the dull end of the sewing needle by hand or with a small screwdriver. Tightening a clamp more than necessary may bend a sewing needle and make it unusable for future projects.