A carbide mandrel (German: Ziehdorn) is the internal tool in tube drawing. It sizes the inside diameter of the tube while the drawing die forms the outside diameter. We manufacture fixed mandrels for chain drawbenches, covering tube diameters from 2.5 to 200 mm, and floating plugs for continuous drawing on drum-type benches. Every tool is made to order in Herborn, Germany – since 1948.
What does a mandrel do in tube drawing?
In cold tube drawing, the drawing die controls the outside diameter. Without an internal tool (tube sinking), the wall thickness stays roughly constant and the inside diameter is not precisely controlled. A mandrel or plug closes that gap: the tube is formed in the annulus between die and mandrel, which fixes the inside diameter and smooths the bore. Under the German standard DIN 8584, tube drawing is classified as forming under combined tensile and compressive conditions. Three basic methods are used in practice:
| Method | Internal tool | Result |
|---|---|---|
| Tube sinking | none | OD and ID reduced, wall thickness roughly constant; inside diameter not precisely controlled |
| Plug drawing | fixed or floating plug (mandrel) | wall thickness and diameter reduced, bore smoothed; cross-section reductions up to about 45 % per pass |
| Rod drawing | inserted rod/bar | OD and wall thickness reduced, tight tolerances, both surfaces smoothed |
Fixed carbide mandrels for chain drawbenches
Fixed mandrels are used mainly on chain drawbenches to draw tubes of fixed length. The mandrel is mounted on a mandrel bar, inserted with it into the drawing die, and the tube is formed between die and mandrel. We manufacture fixed carbide mandrels for tube diameters from 2.5 to 200 mm, made to order from your drawing or engineered for your application. Die and mandrel work as a tool pair: both geometries have to match so that inside diameter and wall thickness stay within tolerance. The right carbide grade and a surface finish held within the tightest tolerances give the tool its full service life. On request, each mandrel is supplied with the coating best suited to the application.
Floating plugs for continuous tube drawing
Floating plugs – the tools the German trade calls Mandrillen – are used for continuous drawing of tubes on drum-type drawing benches, where long tubes are drawn from the coil and no mandrel bar can follow. A floating plug holds its position in the deformation zone through its geometry alone: the drawing forces pull it into the die. This is why the geometries of drawing die and plug must be calculated together. We use dedicated software to calculate tool geometry and drawing schedules. The plug runs under high wear, which makes tungsten carbide the standard choice. How drawing angle and bearing length interact is explained in our article on drawing die geometry.
What determines the service life of a carbide mandrel?
Scrap and downtime on a tube drawing line cost many times the price of the tool. Service life is therefore decided at the design stage: we select the carbide grade to match tube material and reduction, and calculate the geometry with our own software. Manufacturing follows with the highest surface quality within the tightest tolerances; much of the final surface finish is still produced by hand polishing with diamond compounds. Our manufacturing page shows how we work. Every tool is inspected with modern measuring equipment, and we supply a measurement report on request. We are certified to DIN EN ISO 9001:2015. When time is short, a large stock of carbide blanks keeps delivery times down – within 24 hours if necessary.
From inquiry to finished tool
- You send us your drawing (PDF, DXF or STEP) or your application data: tube material, dimensions, reduction, machine type.
- We design die and mandrel as a tool pair – geometry from our calculation software, design work in 3D CAD.
- Grinding, polishing and permanent marking (needle embosser or laser) take place at our plant in Herborn-Schönbach.
- Before delivery, every tool is checked with modern measuring equipment; a measurement report is enclosed on request.
Request a quote – upload your drawing or application data and we will get back to you promptly.
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