What is the minimum wall thickness in deep drawing?
The minimum wall thickness in deep drawing - also called the minimum drawable wall - is set by the material, the draw ratio and the corner radius rather than by one catalogue figure, and it is not a single number even on one part: it follows the blank thickness in the first draw, thickens slightly at the open rim, and thins at the punch nose where the material is bent and stretched. Balford's published sensor-housing configurations record walls from 0.25 mm to 1.00 mm, with 0.50 mm the most common value in the catalogue, while larger drawn housings in copper and brass start at about 0.8 mm. Because the value changes along the height, the minimum has to be stated together with the measuring position; a drawing that gives one wall figure and no position cannot be inspected.
Why one wall figure is not enough
A drawn housing starts as a flat blank and is pulled over a punch. Material that was in the blank has to end up in a taller, smaller-diameter shape, so thickness moves rather than staying constant. The result is a gradient: the wall near the bottom radius is usually thinner than the blank, the straight wall sits close to the blank thickness, and the top rim thickens because material from the flange is compressed into it as the flange shrinks.
That is why a note such as "wall 1.0 mm" on a drawing is not a specification. It does not say where the 1.0 mm applies, so the part can pass one measurement and fail the next while both are taken to the same drawing.
Wall thickness in the published catalogue
| Wall thickness (mm) | Configurations |
|---|---|
| 0.50 | 176 |
| 0.40 | 46 |
| 0.30 | 13 |
| 1.00 | 7 |
| 0.80 | 5 |
| 0.25 | 5 |
| 0.60 | 3 |
| 0.45 | 1 |
Three ways wall thickness changes in production
- Thinning during drawing. Material flows and stretches, so the wall of a drawn cup is not the thickness of the blank. Tool radius, clearance and lubrication decide how much thinning happens and where.
- Ironing. Where the wall has to be thinned deliberately while holding both the inside and the outside diameter, the part is ironed through a series of rings rather than drawn again. This is how thin-wall sleeves and solenoid housings are made.
- Machining after forming. Sealing faces, bearing seats and critical functional features are often machined after drawing, because that is where a tight tolerance is actually needed.
What to state on the drawing
- Nominal wall thickness and where it is measured (near the base, on the straight wall, or at a defined height).
- Whether the wall must be held through ironing, and which diameter is the datum.
- Finished surface requirement, because it decides whether the last operation is forming or machining.
- Temperature or corrosion environment, because that decides the grade - and the grade decides what the wall can do.
- If the wall is measured after plating or coating, say so - the deposit adds to the measurement and the drawing must state whether the figure is before or after finishing.
- Where the wall thins at the bottom radius, give a separate minimum rather than letting one global figure cover it.
The three things that decide the achievable minimum
- Draw ratio - how much the blank has to shrink to reach the finished diameter. A deeper draw ratio needs more stages, and each extra stage costs thickness control.
- Material - stainless steel work-hardens faster than low-carbon steel, so it tolerates less thinning per stage before it needs to be annealed.
- Corner radius and punch nose - the tighter the radius, the more the material is stretched at that point, and the thinner the wall becomes there.
How thickness is checked
Wall thickness is checked with outside micrometers at the positions the drawing defines, and cross-checked against the 2.5D optical measuring projector and the instant vision measuring system where the geometry makes a micrometer reading unreliable. Bore-related dimensions are checked with three-point bore micrometers, plug and go/no-go gauges, and a concentricity gauge. Inspection results are recorded per lot and reviewed in the quality routine. Where a feature is critical and the process, geometry, material and inspection conditions allow it, dimensions to 0.001 mm can be agreed in advance - but that is a drawing-confirmed exception for selected machined features, not a standard tolerance for a drawn wall.
What we do not claim
- We are not IATF 16949 certified. Our controls are aligned with IATF 16949 requirements, and we say so rather than claiming the certificate.
- Our quality system is certified to ISO 9001:2015. ISO 14001:2015 has lapsed and is not claimed.
- Bulk heat treatment, slow-wire EDM, passivation, electropolishing, plating, phosphating and liquid painting are subcontracted, with traceable process records. Powder coating is split: large sheet-metal parts run in our own manual booth, small parts are coated by a partner on an automatic line.
- Hot forging, cold extrusion, cold heading, casting and powder metallurgy are bought as near-net pre-forms and finished by machining in-house. We are not a forge, a foundry or a powder-metallurgy plant.
- Walls below the catalogue range are possible on specific parts, but only after a drawing review - we do not quote a minimum as a catalogue figure.
Frequently asked questions
What is the thinnest wall you can draw?
Balford's published sensor-housing configurations record walls from 0.25 mm to 1.00 mm, and 0.50 mm is the most common catalogue value; larger drawn housings in copper and brass start at about 0.8 mm. The achievable minimum depends on the material, the draw ratio and the corner radius rather than on a fixed catalogue number. Send the drawing and we will tell you whether the wall you need is reachable, and what it does to the number of drawing stages.
Why does the wall thickness change along the height?
Because the material is moved, not added. The flange shrinks into the wall as the part is drawn, so the rim thickens; the material stretched over the punch nose thins. In an ironed wall the thinning is deliberate and set by the die clearance.
How should the wall be dimensioned on the drawing?
As a nominal with a tolerance band plus an explicit measuring position - for example, 12 mm above the bottom face. Also state whether the figure applies before or after plating or coating, and give a separate minimum where the bottom radius thins.
Can you hold the wall thickness after ironing as well as the surface finish?
Ironing sets the wall and the surface in the same operation, so the two are specified together. If both are critical, they need to be on the drawing together, and the die set has to be built for that combination.