What Is Deep Drawing? A Practical Guide to Deep Drawn Brass Parts
Deep drawing turns flat brass strip into seamless cups, shells and caps. Here is how the process works, step by step, and what it means for the parts you buy.
Deep drawing is a cold-forming process that turns a flat sheet-metal blank into a seamless, hollow part. A punch forces the blank into a die cavity, and the metal flows inwards and downwards to form a cup. When the depth of the part is greater than its radius, the process is called deep drawing. It is how most snap button caps, eyelet barrels, rivet caps and many decorative brass shells are made.
At Ata Buttons we have deep drawn brass in our Istanbul factory since 1999. This guide explains the process in plain terms, so you know what to expect when you source deep drawn brass components.
The Basic Tooling: Punch, Die and Blank Holder
Every deep drawing operation uses three main elements:
- The punch pushes the material and gives the part its inside shape.
- The die has a cavity with a carefully radiused entry. It defines the outside shape.
- The blank holder (or pressure pad) clamps the edge of the blank. It controls how fast metal is drawn in and stops the flange from wrinkling.
The radii on the punch and die, the clearance between them and the blank-holder pressure all decide whether a part draws cleanly or tears.
Step by Step: From Brass Strip to Finished Part
1. Blanking
A round (or shaped) blank is cut from brass strip. The blank's diameter is calculated from the surface area of the finished part, with allowance for trimming.
2. First draw
The blank is drawn into a shallow cup. In each draw, the cup diameter can only be reduced by a limited amount before the wall thins too much or tears. This is described by the limiting draw ratio.
3. Redraws
Deeper parts need several redraws. Each one reduces the diameter and increases the depth. Small garment components such as snap caps are often produced on progressive or transfer tooling, where the strip moves through every stage in sequence.
4. Trimming, piercing and forming
The uneven edge left by drawing is trimmed. Holes are pierced, flanges are rolled or curled, and logos, knurls or patterns are embossed into the surface.
5. Annealing (when needed)
Brass work-hardens as it is drawn. For very deep parts, an intermediate anneal restores ductility so the next draw can proceed without cracking.
6. Cleaning and plating
Drawing lubricants are removed, and parts are electroplated: nickel, antique brass, gold, black nickel, gunmetal or a nickel-free finish. They can also be lacquered or painted.
7. Inspection
Dimensions, finish and function are checked. For snap buttons, that includes the snap engagement force, before parts are packed.
Why Deep Drawn Parts Are Different
- Seamless: no welds or joins, so the part cannot split along a seam.
- Strong for their weight: work-hardening during drawing increases strength in the wall.
- Repeatable: once tooling is proven, thousands of identical parts can be made per hour.
- Finish-friendly: the smooth drawn surface takes plating evenly.
Common Defects and How They Are Avoided
| Defect | Typical cause | Prevention |
|---|---|---|
| Wrinkling in the flange | Blank-holder pressure too low | Correct pad pressure and blank size |
| Tearing at the base radius | Draw ratio too high, radius too tight | More draw stages, larger radii, annealing |
| Earing (wavy rim) | Directional properties of the strip | Material selection, trimming allowance |
| Scratches / galling | Poor lubrication or worn tooling | Lubricant control, tool polishing |
What to Send for a Deep Drawn Brass Quote
To get a realistic price and lead time, include a drawing (PDF, DXF or STEP) or a sample, the wall thickness, critical dimensions, the finish you need, and your order and annual quantities. See our deep drawn brass components page for the full checklist. If you are comparing processes, read deep drawing vs stamping next.
