Full Thread
A full thread is a screw thread cut or formed to its intended depth and profile across the specified thread length, with no partial or incomplete section within the usable engagement zone. In CNC machining, it commonly means a thread that runs the full required length of the feature rather than a truncated or relief-limited thread.
On the shop floor, a full thread callout drives tool selection, cycle planning, and inspection. In CNC turning, the programmer picks a threading insert and infeed method, sets the cycle to reach proper minor diameter and length, and includes enough approach and exit distance to stabilize spindle speed before engagement. For internal threads, the tap drill or pilot bore must be correct: an undersized hole overloads the tool, while an oversized hole reduces thread engagement and can let a go gauge pass while the joint fails in service. When thread milling, the toolpath must generate the full helix and account for lead-in and lead-out so the thread is usable across the entire engagement length, not just visually continuous in CAD. Final inspection uses go/no-go gauging, pitch diameter measurement, and verification that usable threads extend to the specified depth without interrupted crests from chamfers, burrs, or incomplete tool travel.
Does 'full thread' mean full theoretical profile to the crest root, or just the required engagement length?
In shop usage, it usually means the thread exists over the full specified axial length; actual crest/root form still depends on class, tool geometry, material, and standard thread tolerances.
Is 'full thread' the same as 'full depth thread'?
Not exactly. Full depth refers to geometric thread depth relative to the profile, while full thread in production commonly refers to the thread being present for the entire specified length of engagement.
How do you verify a full thread on the floor?
Use the specified thread gauge, confirm pitch diameter and class compliance, and inspect for complete thread form to the programmed length with no premature termination from chamfer, relief, or tool deflection.