Cam out (also cam-out or camming out) is a process by which a screwdriver slips out of the head of a screw being driven once the torque required to turn the screw exceeds a certain amount. [1] Repeatedly camming out damages the screw, and possibly also the screwdriver, and should normally be avoided.
The Phillips screwdriver design has a tendency to cam out during operation due to angled contact surfaces which create an axial force pushing the driver out of the recess as torque is applied. Despite popular belief, [2] there is no clear evidence that this was a deliberate design feature. When the original patent application was filed in 1933, the inventors described the key objectives as providing a screw head recess that (a) may be produced by a simple punching operation and which (b) is adapted for firm engagement with a driving tool with "no tendency of the driver to cam out". [3]
Nevertheless, the tendency of the Phillips screw to easily cam out was found to be an advantage when driven by power tools of that time which had relatively unreliable torque limiter clutches, as cam-out protected the screw, threads, and driving bit from damage due to excessive torque. [4] : 85–86 A follow-up patent refining the Phillips screw design in 1942 describes this feature and further argues that if screw drive clutches were perfect, a screw recess with zero vertical contact angles (and thus no axial cam-out force) could be utilized, but claims that where these have been tried, unsatisfactory results on assembly lines have prevailed since the driving bits would not cam out in time to prevent damage. [5]
Several later designs derived from Phillips, like Pozidriv and Supadriv were designed to reduce or eliminate the propensity to cam-out. In recent years, power tools can more accurately control fastener torque, and it is typical for precision engineered products to be assembled with Torx or Pozidriv head screws, [6] which have been specifically designed not to cam out.
Robertson screws are commonplace in Canada, and significantly reduce cam-out when compared to Phillips screws.
A screwdriver is a tool, manual or powered, used for turning screws. A typical simple screwdriver has a handle and a shaft, ending in a tip the user puts into the screw head before turning the handle. This form of the screwdriver has been replaced in many workplaces and homes with a more modern and versatile tool, a power drill, as they are quicker, easier, and can also drill holes. The shaft is usually made of tough steel to resist bending or twisting. The tip may be hardened to resist wear, treated with a dark tip coating for improved visual contrast between tip and screw—or ridged or treated for additional 'grip'. Handles are typically wood, metal, or plastic and usually hexagonal, square, or oval in cross-section to improve grip and prevent the tool from rolling when set down. Some manual screwdrivers have interchangeable tips that fit into a socket on the end of the shaft and are held in mechanically or magnetically. These often have a hollow handle that contains various types and sizes of tips, and a reversible ratchet action that allows multiple full turns without repositioning the tip or the user's hand.
A drill is a tool used for making round holes or driving fasteners. It is fitted with a bit, either a drill or driverchuck. Hand-operated types are dramatically decreasing in popularity and cordless battery-powered ones proliferating due to increased efficiency and ease of use.
Henry Frank Phillips was an American businessman from Portland, Oregon. The Phillips-head ("crosshead") screw and screwdriver are named after him.
A torque wrench is a tool used to apply a specific torque to a fastener such as a nut, bolt, or lag screw. It is usually in the form of a socket wrench with an indicating scale, or an internal mechanism which will indicate when a specified (adjustable) torque value has been reached during application.
Drill bits are cutting tools used in a drill to remove material to create holes, almost always of circular cross-section. Drill bits come in many sizes and shapes and can create different kinds of holes in many different materials. In order to create holes drill bits are usually attached to a drill, which powers them to cut through the workpiece, typically by rotation. The drill will grasp the upper end of a bit called the shank in the chuck.
Torx is a trademark for a type of screw drive characterized by a 6-point star-shaped pattern, developed in 1967 by Camcar Textron. A popular generic name for the drive is star, as in star screwdriver or star bits. The official generic name, standardized by the International Organization for Standardization as ISO 10664, is hexalobular internal. This is sometimes abbreviated in databases and catalogs as 6lobe. Torx Plus,Torx Paralobe and Torx ttap are improved head profiles.
A limited-slip differential (LSD) is a type of differential that allows its two output shafts to rotate at different speeds but limits the maximum difference between the two shafts. Limited-slip differentials are often known by the generic trademark Positraction, a brand name owned by General Motors.
A socket wrench is a type of spanner that uses a closed socket format, rather than a typical open wrench/spanner to turn a fastener, typically in the form of a nut or bolt.
A machine taper is a system for securing cutting tools or toolholders in the spindle of a machine tool or power tool. A male member of conical form fits into the female socket, which has a matching taper of equal angle.
A Robertson screw, also known as a square screw or Scrulox, is a type of screw with a square-shaped socket in the screw head and a corresponding square protrusion on the tool. Both the tool and socket have a slight taper. Originally designed to enable the screws to be made using cold forming of the heads, the taper has two other advantages which have helped popularize it: it makes inserting the tool easier, and helps keep the screw on the tool without the user having to hold it there. The Robertson screw is specified as ANSI Type III Square Center.
An impact wrench is a socket wrench power tool designed to deliver high torque output with minimal exertion by the user, by storing energy in a rotating mass, then delivering it suddenly to the output shaft. It was invented by Robert H. Pott of Evansville, Indiana.
An impact driver is a tool that delivers a strong, sudden rotational force and forward thrust. The force can be delivered either by striking with a hammer in the case of manual impact drivers, or mechanically in the case of powered impact drivers.
A screw gun is similar to a power drill, but designed specifically for driving screws. A screw gun looks like a drill, but has a "nose" instead of a chuck. The nose holds an interchangeable 0.25 inches (6 mm) shank bit, commonly known as a tip. The most common types of tips are 1 inch (25 mm) #2 phillips, T25 Torx, and flatheads. The nose on either type of screw gun can be adjusted to countersink screws to the desired depth. The user must apply pressure to the bit to engage the clutch and drive the screws.
Computer case screws are the hardware used to secure parts of a PC to the case. Although there are numerous manufacturers of computer cases, they have generally used three thread sizes. The Unified Thread Standard (UTS) originates from the United States, while the ISO metric screw thread is standardized worldwide. In turn, these thread standards define preferred size combinations that are based on generic units—some on the inch and others on the millimetre.
A screw and a bolt are similar types of fastener typically made of metal and characterized by a helical ridge, called a male thread. Screws and bolts are used to fasten materials by the engagement of the screw thread with a similar female thread in a matching part.
A torque screwdriver is a screwdriver with components that ensure tightening to a specified torque, ensuring tightening which is sufficient, but not excessive. An insufficiently tightened screw connection may loosen in operation, and excessive tightening can damage parts; for example, if the nuts holding the wheel of a car in place are too loose, or damaged by overtightening, a wheel may come off at speed. Torque screwdrivers are used in mechanical production, manufacturing, and maintenance; their use is part of quality assurance.
A bolt is a form of threaded fastener with an external male thread requiring a matching pre-formed female thread such as a nut. Bolts are very closely related to screws.
The pentalobe security screw, or pentalobe screw drive, is a five-pointed tamper-resistant system used by, but not limited to, Apple in their products. Pentalobe screws were adopted by Apple starting in 2009, when they were first implemented in the 15-inch MacBook Pro. They have since been used on other MacBook Pro, MacBook Air and iPhone models. Apple attracted criticism upon the introduction of the pentalobe screw; it was seen by some as an attempt to lock individuals out of their devices. In response, inexpensive pentalobe screwdrivers, manufactured by third parties, have become relatively easy to obtain.
A hex key is a simple driver for bolts or screws that have heads with internal hexagonal recesses (sockets).