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Pipe Threading Dies & Heads

A die chaser is the cutting tool that forms the thread on a pipe; the die head is the body that carries the chasers and holds the pipe on axis. This page lists chaser sets in right-hand BSPT, left-hand BSPT and NPT from 1/8″ to 4″, for steel and stainless steel pipe, along with the heads that carry them.

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Why the chaser, not the machine, sets the thread

A threading machine does not cut a thread; the chaser does. The machine turns the pipe, feeds the head and delivers cutting oil. That is why one machine cuts right-hand BSPT, left-hand BSPT and NPT simply by changing the chaser set.

BSPT is the standard plumbing thread in Europe and Turkey. NPT uses a different thread angle and pitch; the two will start into each other by hand but will not seal. Left-hand threads are used on gas work and where the direction of a joint matters.

Thread formWhere it is used
Right-hand BSPTGeneral water and heating pipework; the standard pipe thread in Turkey
Left-hand BSPTGas and special joints; never mixed with right-hand on one line
NPTUS standard equipment and imported fittings

The thread form comes with the chaser, not with the machine.

Why a steel chaser is not used on stainless

Stainless steel is both harder and stickier in the cut than carbon steel. A chaser ground for steel dulls quickly in it, tears the flank of the thread and leaves a joint that seeps. Separate stainless sets are listed for that reason.

Cutting oil is the second half of the answer: it cools the cut and carries the chip out of the root of the thread. A thread cut dry ruins the chaser and the pipe together.

How chaser, head and stock work together

The head positions the chasers for one pipe size and centres the pipe. The stock is the ratchet that turns the head by hand; on a machine the motor does that work. The three are a system: not every chaser fits every head, and not every head fits every stock.

Each product page states the machine or head series it belongs to by Virax catalogue number (1620, 1621, 1240-1245). When ordering, the machine number matters as much as the size.

Frequently Asked Questions

  • Is a die chaser the same as a die head?

    No. The chaser is the cutting part and it decides the thread form. The head is the body that carries the chasers and centres the pipe. One head works with different thread forms in its size.

  • Can BSPT and NPT be used interchangeably?

    They should not be. The thread angle and pitch differ; the joint will turn together by hand but will not seal properly, and on a pressurised line it eventually leaks.

  • How do I know which chaser fits my machine?

    Every product page states the compatible machine by catalogue number, for example 1620-1630 or 1621. Match it against the number on your machine.

  • Can a steel chaser thread stainless pipe?

    It can, but it dulls fast and tears the thread surface. Chasers made for stainless last longer and give a thread that seals.