Wire drawing dies and bar and tube drawing dies are the two basic forms of the tungsten carbide drawing die, and both work on the same principle: a carbide core reduces the cross-section of the material pulled through it. The wire drawing die (German: Ziehstein) handles wire and strand-like material with bore sizes from 0.2 to 150 mm; the bar and tube drawing die (German: Ziehmatrize) is the much larger cased tool for bars and tubes, with die cases up to Ø 450 mm. Fritz Leng has made both to order in Herborn, Germany since 1948 — geometry calculated for your material and reduction, hand-polished, shipped within 24 hours when needed.
Wire drawing die or bar and tube drawing die?
| Criterion | Wire drawing die | Bar and tube drawing die |
|---|---|---|
| Drawn stock | wire and strand-like material | bars and tubes |
| Typical processes | wire drawing, single- and multi-pass | tube sinking, plug drawing, rod drawing |
| Dimensions | bores 0.2 to 150 mm | core and case dimensions up to case Ø 450 mm |
| Construction | carbide core in a steel case | carbide core in a steel case, much larger |
| Works together with | the drawing schedule across several passes | carbide mandrels and plugs in plug and rod drawing |
| German term | Ziehstein | Ziehmatrize |
Request a quote — state material, starting and finished size, or send your drawing (PDF, DXF, STEP): we recommend the right tool type and geometry and prepare a quotation. English inquiries are welcome.
Request a quoteTungsten carbide wire drawing dies
What are carbide wire drawing dies used for?
Carbide wire drawing dies are used to draw strand-like material, above all wire for the cable, tube and bar industries. In each draft the wire is pulled through the polished bore of the die; it becomes longer and thinner and takes on the exact shape of the opening. Under the German standard DIN 8584, wire drawing is classified as combined tension-compression forming: the pulling force acts on the exit side, while the actual forming is done by the pressure of the die wall.
What makes a carbide die run trouble-free?
Two things must be right from the start: high-quality carbide in the correct grade, and high-quality steel for the case. Both have to be matched in their composition to the individual application. The function and the service life of the die are then determined by the correct geometry of the drawing angle and bearing length, and by a mirror polish of the working surface.
Calculation and 3D CAD software help us determine the ideal parameters for your wire and reduction. We machine only carbide from leading global suppliers, and on request we deliver a measurement report with every die (see Quality).
Entry radius and entrance angle
The bore profile of a drawing die consists of zones that merge into one another: entry radius and entrance cone, drawing angle, and bearing length. The entry radius, also called the entrance angle, guides the incoming wire and centers it in the die, even when the wire enters in spirals. The entrance cone also feeds lubricant into the die: without a sufficient film, the wire reaches the forming zone dry and its surface suffers. Entry radius and entrance cone may remain unpolished.
Drawing angle: where the entire reduction happens
The drawing angle, often called the approach angle, is the most important section of a wire drawing die. The entire reduction in area and the compacting of lubricant onto the incoming wire surface occur here. The efficiency of any die is determined by the design and accuracy of this approach zone, which must be ground to an accurate conical angle with a smooth surface finish. It must be straight-sided along its entire length, without a distinct radius or blended contour.
The approach angle does all the work in the die and is the first place to look when designing a die or troubleshooting a drawing problem. It has three major functions: it lubricates the surface of the wire prior to reduction by producing pressure that promotes lubricant flow; it reduces the diameter of the incoming wire, which imparts a denser structure, a harder surface and an improved finish; and it sizes the material at the point where it meets the bearing. Using the wrong angle or the wrong reduction is the main cause of drawing failures and rejected wire.
Bearing length: 25 to 66 % of the die diameter
The bearing length, also called the sizing zone or cylinder, controls the diameter of the drawn wire, guarantees its roundness and straightness, and produces an even, smooth surface. To produce quality wire, the bearing must therefore be round, parallel and held to a minimal size tolerance.
To avoid premature fatigue of the tool, the bearing length should be between 25 and 66 % of the die diameter. A worked example: a die with a diameter of 2.54 mm and a bearing proportion of 35 % has a bearing length of 0.889 mm.
| Material being drawn | Bearing length (share of die diameter) | Reason |
|---|---|---|
| Harder materials | approx. 25–35 % | less heat development, lower risk of lubrication faults |
| Softer materials | approx. 50 % | longer usable life of the die |
As long as the die still holds size and enough bearing remains, wear rings can be removed by repolishing. We offer this as a service: reconditioning of carbide drawing dies.
Ceramic dies and coatings
Tungsten carbide is the most widely used die material. A variety of carbide grades, hard-material surface coatings and ceramic dies belong to our product range. Which combination is right depends on your material, drawing speed and required service life. Send us your drawing data and we will advise you. For a detailed comparison of carbide, PCD and ceramic dies, see our article on wire drawing die geometry and material selection.
How your die is made at Leng
You send us your requirement or drawing; we design the die. Drawing angle, bearing length and carbide grade are calculated with our own software for your material and reduction. Bores from 0.2 to 150 mm are ground on internal grinding machines and calibrated on an automatic polishing and calibrating machine, before our staff produce the surface finish by hand with diamond pastes. Every die is inspected with modern measuring equipment and permanently marked by dot-peen or laser; a measurement report is available on request. We are certified to ISO 9001:2015, valid until 16 December 2028.
Bar and tube drawing dies
What is a bar and tube drawing die?
A bar and tube drawing die is the outer tool in cold drawing: the stock is pulled through the die, the pulling force acts on the exit side, and the actual forming is done by the pressure of the die wall. Bar and tube drawing dies do the same job as wire drawing dies at much larger dimensions, which is why core and case sizes reach well beyond the wire range. The internal profile follows the same logic in both tool families: entrance, reduction cone and bearing length together determine size accuracy and surface quality. The interplay of these zones is explained in our article on drawing die geometry.
Which tube drawing processes do these dies serve?
For cold drawing of tubes, published steel-tube literature (among others Wirtschaftsvereinigung Stahlrohre, "Herstellverfahren") distinguishes three basic methods:
| Process | Internal tool | Effect |
|---|---|---|
| Tube sinking | none | Outer and inner diameter are reduced, wall thickness stays roughly constant |
| Plug drawing | fixed or floating plug | Wall thickness and diameter are reduced, the inner surface is smoothed; cross-section reduction up to about 45 % per pass |
| Rod drawing | inserted mandrel bar | Outer diameter and wall thickness are reduced; close tolerances, both surfaces smoothed |
In every method the drawing die forms the outer contour. In plug and rod drawing it works together with an internal tool. We also make the matching internal tools: fixed carbide mandrels and plugs for tube diameters from 2.5 to 200 mm, so die and mandrel arrive matched to each other from one workshop.
What sizes do we supply?
We supply bar and tube drawing dies in all common core and case dimensions, up to die cases of Ø 450 mm. This covers large bar and tube cross-sections that are far outside the range of standard wire dies. Our machinery grinds bores from 0.2 to 150 mm on internal cylindrical grinding machines; every bore is polished afterwards.
Each die is made to order, to your specification or to your drawing, and matched to the drawn material, the dimensions and the reduction per pass. Every tool receives permanent marking by needle engraving or laser, so it stays clearly identifiable in your drawing schedule and for reordering. For geometries outside the standard program we make custom carbide tooling to customer drawings.
What determines the service life of a drawing die?
A very high surface finish and a geometry matched to the drawing process give the die its maximum service life. Neither happens by accident. Our calculation software assists in working out drawing schedules and in determining the optimal tool geometry, for example when you change the drawn material or the reduction per pass. After internal grinding, the bore is polished; the final finish is still produced largely by hand polishing with diamond pastes. Modern measuring equipment checks every bore, and on request we include a measuring report with the delivery: documented quality to ISO 9001:2015.
How does an inquiry work?
Since 1948 we have made nothing but drawing tools for wire, bar and tube production, to order, in Herborn, Germany. The process is straightforward:
Inquiry:
You state the drawn material, dimensions and reduction, or send your drawing (PDF, DXF, STEP). English inquiries are welcome.
Design:
We work out geometry and drawing schedule with our calculation software and 3D CAD.
Manufacturing:
Internal grinding, polishing, permanent marking by needle engraving or laser.
Inspection and delivery:
Measuring report on request. A large stock of raw material keeps delivery times short, within 24 hours if necessary.
Reconditioning and accessories
Worn tools do not have to be replaced: our reconditioning service for carbide drawing dies regrinds them to the next possible size, giving you a tool in as-new condition at a fraction of the cost of a new one.
For polishing and reworking, diamond suspensions in grit sizes from 3 to 45 µm and electroplated diamond grinding pins are available from stock; details are on our accessories page. They are the same polishing supplies we use in our own workshop every day.
