Our metric hex dies and round adjustable dies, manufactured to DIN 382, DIN 223, and DIN EN 22568, cut and repair external threads on bar, stud, and bolt. Hex dies are turned with a standard spanner for fast field work, while round adjustable dies allow fine control of thread fit in a die stock or on a machine.

Hex Dies and Round Adjustable Dies in Metric Sizes

What Is a Threading Die?

A threading die is a hardened cutting tool that forms an external thread on a round bar, rod, or stud. It works as the counterpart to a tap, which cuts internal threads. As the die is turned onto the workpiece, cutting edges around its bore remove material in a controlled spiral, leaving a thread of the correct pitch, form, and diameter. Dies are also used to clean up damaged threads on existing fasteners, restoring fit without replacing the part.

At Metric Specialties we stock both hex dies and round adjustable dies. A hex die has six external flats so it can be driven with a common spanner or socket, which makes it the practical choice for maintenance, repair, and site work where a die stock is not to hand. A round adjustable die is split across its body and held in a die stock, allowing a small change in cut diameter so you can dial in a tight or free running fit and take a heavy thread in two passes.

Key Features and Benefits

• Cuts and Repairs External Threads: Produce a new thread on plain bar, or chase and restore a damaged thread on an existing bolt or stud.
• Hex Drive Convenience: Hex dies turn with an ordinary spanner or socket, which suits toolbox, field, and vehicle repair work.
• Adjustable Fit Control: The split body of a round die lets you set the cut diameter for a tight or free running class of fit.
• Full Metric Coverage: Coarse and fine pitches across a broad diameter range, so you can match the thread on the part in front of you.
• Hardened Cutting Edges: Carbon steel for occasional use and high speed steel for repeated cutting in tougher materials.

Materials and Finishes

• Carbon Steel: An economical choice for chasing, cleaning, and light occasional thread cutting in mild steel and softer metals.
• High Speed Steel: Holds a keen edge at higher cutting temperatures, giving longer life and cleaner threads in steel, stainless, and alloy.
• HSS with Surface Treatment: Coated variants that reduce friction and built up edge when cutting stainless and sticky materials.

Standards Compliance

• DIN 382 covers hexagon dies for metric ISO threads.
• DIN 223 and DIN EN 22568 cover round split dies and their die stock dimensions.
• ISO 68-1 and ISO 965 define the metric thread profile and the tolerance classes the die produces.

Common Applications and Industries

Threading dies are used in maintenance workshops, fabrication shops, vehicle repair, agriculture, marine engineering, and toolrooms of every size. The most common job is thread repair, where a bolt or stud has been damaged by corrosion, impact, or a cross threaded nut, and a die restores the thread rather than forcing removal of a seized or captive component.

The second common job is producing a thread on a plain bar to make a custom stud, tie rod, or adjuster to a length no catalogue fastener offers. Hex dies suit fieldwork, on site plant, and anywhere a spanner is the only tool available, while round adjustable dies suit bench work and small batch production where fit tolerance and finish matter, including in a lathe tailstock die holder.

How to Choose the Right Die

Begin with the thread you need to produce, taking both the diameter and the pitch, since a metric size such as M10 exists in coarse and fine pitches that are not interchangeable. Measure the existing thread with a pitch gauge if you are repairing rather than cutting new, and confirm the major diameter with a caliper before selecting the die.

Then choose the die style by how you will drive it. Pick a hex die where a spanner is the tool at hand and the job is chasing or a light cut, and pick a round adjustable die where you need fine control of fit, a heavier cut in two passes, or a mount in a die stock or machine holder. Select carbon steel for occasional repair work and high speed steel for repeated cutting or for stainless and alloy. Finally, size the bar correctly, chamfer the leading end, and use a suitable cutting fluid so the die starts square and the thread finishes cleanly.

Size Range and Availability

Available in M1 through M52 in metric coarse and fine pitch, in hex and round adjustable styles, across carbon steel and high speed steel, with matching die stocks and holders.

Why Buy From Metric Specialties

As dedicated metric specialists, we hold hex dies and round adjustable dies in the diameters, pitches, and grades that workshops actually use, backed by clear DIN and ISO references so you can specify with confidence. Every item is sourced to recognised standards and quality controlled, giving you consistent thread form, tolerance, and edge life across repeat orders.

Whether you need a single die for a repair or a full set for a toolroom, our range, technical guidance, and fast dispatch help you find the exact tool for the job. If you are unsure which pitch, style, or material grade suits your work, our team can help you match the right product to your thread, material, and method, so your threads cut cleanly and run true.

Frequently Asked Questions

1. What is a threading die used for?

A die cuts an external thread onto a round bar or rod, and chases or repairs a damaged thread on an existing bolt or stud. It is the external counterpart to a tap.

2. What is the difference between a hex die and a round adjustable die?

A hex die has six flats and is turned with a standard spanner or socket, which suits field and repair work. A round adjustable die is split and held in a die stock, allowing you to adjust the cut diameter for a tight or free fit.

3. Can a die cut a full depth thread in one pass?

A hex die is intended mainly for chasing and light cuts in one pass. For a full depth thread in tougher material, a round adjustable die set slightly open for a first pass and closed for a finishing pass gives a cleaner result and less tool strain.

4. What bar diameter do I need before threading?

Start with a bar at or fractionally below the nominal major diameter of the thread. Oversized bar overloads the cutting edges, while undersized bar gives a shallow thread with reduced strength.

5. Should I choose carbon steel or high speed steel?

Carbon steel is economical and suits occasional chasing and light work in mild steel. High speed steel holds its edge at higher temperatures and is the better choice for repeated cutting and for stainless, alloy, and harder materials.

6. Do I need cutting fluid?

Yes. A suitable cutting fluid reduces heat and friction, improves thread finish, and extends the life of the die. It matters most in stainless and alloy steels.

7. How do I start a die square to the bar?

Chamfer the leading end of the bar, present the tapered starting face of the die first, and apply light even pressure while turning until the first threads bite. A die stock or tailstock holder keeps the die square on a critical job.

8. Can dies cut both coarse and fine metric threads?

Yes. Metric dies are supplied in coarse and fine pitch. A given diameter such as M10 exists in more than one pitch, so confirm the pitch with a gauge before selecting the die.

9. What sizes do you stock?

We stock M1 through M52 in coarse and fine pitch, in hex and round adjustable styles, across carbon steel and high speed steel.

10. Can I use a die in a lathe?

Yes. A round die held in a tailstock die holder is a common way to produce a square, accurate thread on a lathe. Run at a low speed and use cutting fluid.