Short definition
A hacksaw is a manual fine-toothed saw with a tensioned, replaceable blade. In plumbing, it’s the fallback when a tubing cutter can’t rotate around the pipe — under sinks, in wall cavities, on stuck threaded steel. Mini or junior hacksaws are the under-cabinet workhorse.
What it is
The full-size hacksaw uses a 12-inch blade in a tensioned bow frame. Mini and junior models hold a shorter blade segment at one end only, sacrificing length for reach into tight cavities. Blades are graded by teeth-per-inch (TPI): 24 TPI for thin metal and copper, 18 TPI for thicker steel, 32 TPI for very thin tubing. The rule: at least three teeth on the workpiece at all times, or the saw skips and bends.
Blades cut on the push stroke. Install them with the teeth pointing forward (away from the handle). Tension matters — a loose blade wanders out of square.
Why it matters to a homeowner
For new copper installs, a tubing cutter is faster and produces a square, deburrable cut. The hacksaw earns its place in three situations: cutting through a stuck threaded supply line that won’t unscrew, cutting copper in a tight wall cavity where a tubing cutter has no swing room, and trimming toilet bolts flush after install. A $10 hacksaw has saved more weekends than most power tools.
Common variants and not the same as
- Hacksaw vs. tubing cutter. Tubing cutter is faster on copper; hacksaw is the fallback when geometry blocks rotation.
- Hacksaw vs. reciprocating saw. Recip is faster but less controlled. Hacksaw for surgical cuts near other plumbing or electrical; recip for demo.
- Hacksaw vs. plastic-pipe saw. Dedicated PVC saws have coarse non-set teeth that don’t grab. A hacksaw works on plastic but leaves more burr.
Common failure modes
- Blade backward. Teeth point toward handle — the saw won’t cut.
- Low tension. Blade bends; cut wanders.
- Wrong TPI. Too coarse on thin copper grabs and skips, scoring the pipe.
- Bound kerf. Cut pipe drops into the kerf and pinches the blade — cracks under torque.