Thread cutting by hand - this is how it is done professionally

Often times, screw connections on the top of a pipe make sense. A thread required for this can also be cut by hand without any problems. The following instructions reveal what you have to pay attention to, how to proceed correctly and which tools are used where.

That's what matters

  • Internal or external thread
  • material
  • Drilling diameter
  • Also read - Pre-drilling a core hole for thread cutting
  • Also read - pre-drilling a thread is precision work
  • Also read - Cutting a thread in stainless steel

Internal or external thread

Different tools are used depending on whether an internal or external thread is required. The procedure is also fundamentally different for the two types of thread.

inner thread

Internal threads are cut into the interior of a pipe. Taps are used here. When tapping by hand, the tap is clamped in a so-called tap wrench.

As an alternative to the tap wrench, a tool holder that resembles a ratchet and also works on the same principle can be used. Screwing in is easier, but removing the chips when using a tool holder is usually more time-consuming.

Overall, three different thread cutters are used for cutting internal threads, which always form a related set: a printer - in a gross and a fine variant - and a finish cutter.

The drill channel should be prepared in the internal thread with a countersink to obtain an accurate threaded cut.

External thread

The external thread is made with a so-called cutting iron. The cutting iron is clamped in a cutting iron holder.

When cutting an outer thread - as well as in the internal thread - a suitable cutting oil is required. It ensures a clean threaded cut and protects the blades of the cutting iron.

material

Thread can be cut into different materials. In most cases, the metal will be, but also wood and plastics can be provided in the same way with threads.

With metals in particular, you can find out whether a material can be processed with the file test. Move the file over the surface of the material while applying slight pressure. It must have filing marks in order to be suitable for cutting a thread.

Drawn round bars are best suited for internal threads. They are also the cheapest option.

Drilling diameter

The diameter of the drill and the diameter of the thread cutter must always be precisely matched to one another.

The pre-drilling is done with a slightly smaller diameter than the size of the screw that will later be in the thread. Thread dimension x 0.8 is suitable as a rough approximation. But there are also tables for reference.

Cutting threads by hand (external thread) - explained step by step

  • Round bar
  • Cutting oil
  • Die
  • Die holder
  • file
  • Possibility to fix the round rod

1. Fix the round rod

Fix the round rod upright so that it cannot slip.

2. Filing

File the upper end of the rod slightly conically in the area of the intended thread. This allows the die to grip better. Then file a tapered point.

3. Prepare cutting dies

Insert the die in the die holder and fix it. Moisten with cutting oil. This has to be repeated several times during the cutting process to ensure a clean cut and avoid blade wear.

4th. threading

Place the die exactly horizontally and turn it clockwise with the die holder. Turn back occasionally to break the chips. The chips are then discharged through the chip holes.

Tips & tricks When cutting inner threads, it may be more advantageous to use a wind iron instead of the tool holder, as the chips can be easily removed by returning the wind iron back. With the tool holder a turning back is not possible.