A V block is a device used to hold a round piece of stock secure. Typically used in drilling and machining processes, the V block offers the round piece of wood or steel stock in a cradle-like bed of support. The V block is then able to be placed in a vice or clamp and secured to further steady the work piece. The typical V block is constructed of heavy steel or aluminum to prevent distortion from occurring when the block is clamped to the work piece. The device also has screw clamps or locking devices affixed to it to lock the work piece in once it is properly positioned.
By aligning the work tool with the center of the V block, the absolute center of the round stock is able to be drilled or machined when it is placed in the block. This removes any margin for error in most machining process, provided the stock is securely fastened into the V block. Many types of blocks are magnetic and use a charge to securely hold the steel work piece in lieu of clamps. These are typically electro-magnets that are easily switched on and off in order to easily position and remove the work piece.
Some V blocks are used in vise jaws to effectively hold tubing and pipe when it is being fastened into a vise. This style uses a V-shaped block on each jaw of the vice. As the vice is tightened, the two Vs intersect and form a kind of circle around the pipe. Used when cutting and working on round stock, this version of V block prevents the flattening of the round pipe or stock when it is clamped into a vise.
A similar fastening method is used in tubing flaring kits. The hollow metal tubing is placed in a type of V block and secured so that the flare can be screwed into the tubing, thereby creating a flared fitting. Automobile brake lines as well as fuel and other fluid lines are all created with the assistance of this type of device.
A similar style of block clamp is used to repair fiber-optic cable. In this application, the cable is placed into the V and secured prior to the removal of the cable's protective outer covering. The block allows a repair crew to work on the many small strands of cable without fear of the entire component moving and creating further damage to the fiber optics.