Definition
Precision-machined metal blocks with a V-shaped groove cut into the top, used in aircraft maintenance shops to support a cylindrical workpiece — such as a shaft, crankshaft, or tube — so it can be inspected, measured, or machined while held steady on its centerline. V-blocks are typically used in matched pairs and often include a clamp to hold the work in place.
Plain English
A pair of small metal blocks with a V-shaped notch on top. You lay a round part across them so it sits perfectly straight and can't roll while you measure or work on it.
Context Anchor
Seen in aircraft maintenance, especially when working with round parts such as tubing, rods, shafts, or bolts on a bench or machine.
Derivation
Named for the V-shaped groove cut into the top face of each block. The V-shape is what holds a round object naturally on its centerline — any cylinder of any diameter will rest evenly on the two angled surfaces of the V.
Why Pilots Care
A round part that is not held securely can be drilled off-center, measured incorrectly, damaged, or made unsafe for use on an aircraft.
Analogy
Think of a hot-dog bun: a round object naturally settles into the groove and can't roll sideways. V-blocks do the same job, but precisely machined so the part sits exactly on its true center.
Intuition Check
Do not confuse V-blocks with V-speeds. Here, the V refers to the V-shaped groove in the block, not an aircraft speed.
Example Sentence 1
The mechanic placed the propeller shaft on a pair of V-blocks and used a dial indicator to check it for straightness.
Example Sentence 2
V-blocks kept the axle perfectly supported while the technician checked it for straightness after a hard landing.