A tapping machine cuts internal threads in drilled holes by turning a tap in, then reversing it out. It feeds the tap at the thread pitch and limits the torque, so taps break less often than with hand tapping or a drill press. Arm tapping machines with a swinging arm are common in workshops for tapping large or heavy parts quickly.
Quick facts
- Main types
- Arm (articulated), servo electric, pneumatic, lead screw, multi-spindle
- Typical tap range
- About M2–M24 on arm machines; larger on heavy units
- Reversing
- Automatic at set depth or by torque
- Feed
- By the tap itself or a lead screw matched to the pitch
- Tap holding
- Quick-change collets with torque clutches
- Coolant
- Tapping oil by mist or brush
Main parts
- Motor (electric servo, hydraulic or air) that turns the tap
- Spindle with forward and reverse
- Quick-change tap holder with an overload clutch
- Articulated arm that keeps the tap upright over the work (arm type)
- Depth stop or programmable depth (servo type)
- Base or table to clamp the work
Tapping machine or drill press?
| Tapping machine | Drill press with tapping attachment | |
|---|---|---|
| Tap breakage | Low, torque limited | Higher |
| Speed on many holes | Fast, quick reverse | Slower |
| Large or heavy parts | Arm reaches over the part | Part must fit under the spindle |
| Thread depth control | Precise | Manual |
Good to know
- Servo arm machines set speed and depth per tap size and count holes
- Form taps need more torque but make stronger, chip-free threads
- Blind holes need spiral-flute taps and a depth stop
- Most CNC machining centres tap rigidly, so tapping machines handle extra holes and fabrications
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Questions
- What is an arm tapping machine?
- A tapping head on a jointed arm that swings over a work table and keeps the tap square to the surface, so holes anywhere on a large part can be tapped quickly.
- Can a tapping machine tap stainless steel?
- Yes, with the right taps, lower speed and good tapping oil. Servo machines with torque control help avoid breaking taps in stainless.
- Why not just tap on a CNC machine?
- CNC machines do tap rigidly, but tapping extra holes, welded frames or parts after other operations is cheaper and quicker on a tapping machine.
The figures on this page are typical values for guidance, written by Diemeco from standard engineering practice. They are not a specification: confirm grades and properties with the relevant standard or the supplier's mill test certificate, and tolerances with your workshop. Last checked 22 October 2026.