Draw Bar / Peeled Bar/ Peeled Round Bars/ Peeled Square Bar

Product Description

1. Cold Drawn Bars (Draw Bars)

Cold drawing is a deformation process where a blasted or pickled hot-rolled bar is pulled at room temperature through a hardened tungsten carbide die with a slightly smaller cross-section.

• The Work-Hardening Effect: Because the steel is cold-deformed, its internal crystalline grain structure aligns and compacts. This significantly boosts the material's yield strength and ultimate tensile strength while reducing its ductility (elongation).

• Dimensional Accuracy: Cold drawing delivers exceptionally tight, consistent dimensional tolerances across the entire length of the bar (typically matching h9 to h11 ISO classes).

• Available Shapes: Highly versatile; this process easily accommodates Round, Square, Hexagonal, and Flat geometries.

2. Peeled Bars (Turned Bars)

Peeling is a subtractive machining process where a hot-rolled bar is fed through a high-speed rotary cutting head equipped with multiple carbide inserts.

• Defect Eradication: The rotary head strips away the rough outer skin, completely removing surface seams, scale, micro-cracks, and the decarburized layer created during hot rolling.

• Preserved Core Metallurgy: Since no cold deformation takes place, peeled bars retain the exact mechanical properties (ductility, toughness, and elongation) of the parent hot-rolled material.

• Stress Profile: Peeled bars are virtually free of the directional residual stresses that can cause cold-drawn bars to bow or warp during heavy asymmetrical machining.

3. Geometric Profiles: Rounds vs. Squares

Peeled Round Bars

This is the textbook application of the process. Cylindrical bars are spun through rotary toolheads to achieve near-perfect roundness, technical surface perfection, and a bright finish. They are frequently paired with a secondary centerless grinding or polishing step for high-precision shafts.

The "Peeled Square Bar" Nuance

💡 A Quick Engineering Reality Check: From a strict mechanical standpoint, true rotary toolhead peeling cannot be performed on square geometries because the cutting tips would violently smash into the 90-degree corners.

When you see "Peeled Square Bar" listed in commercial stock catalogs, it is almost always an industry trade phrase for a Surface-Conditioned Bright Square Bar. To achieve this finish on a square or rectangular profile without cold drawing, manufacturers must use one of the following methods:

1. Planing or Milling: Machining the scale off each of the four flat faces sequentially.

2. Abrasive Grinding: Utilizing heavy surface grinders to clear the outer skin.

3. Bright Cold Drawing: Passing it through a square die to scale the rust away mechanically.

Processing Comparison Matrix