Limiting Draw Ratio (LDR) Reference for Deep Drawn Parts
The limiting draw ratio (LDR) is the largest ratio of blank diameter to punch diameter a sheet can survive in a single draw without fracturing: LDR = Db ÷ dp.
Published first-draw values run from about 1.7 for 5052 aluminium to 2.3 for DC06 deep-drawing steel, with 304 stainless steel near 1.8. Every figure on this page is a published reference value with its test conditions stated — so you can judge how far your own setup should sit from the limit.
Published LDR figures disagree with each other. One source puts 304 stainless steel at 1.6–1.8, another at 1.9–2.2, a third at 2.0–2.2. The spread is not error — it is the result of different lubrication, die radii and relative thickness. So instead of quoting a single range as if it were universal, this page gives the commonly published values, the standard conditions behind them, and the corrections that matter more than the material grade.
First-draw limiting draw ratio by material
Reference LDR values below are typical published figures for the standard test conditions listed further down. The design allowable applies a derating of roughly 13% (×0.87) — that margin is what production planning should be built on, because process variability never runs in your favour.
| Material | Standard | Condition | t₀ (mm) | r̄ (typ.) | Reference LDR (first draw) | Design allowable (×0.87) | m₁ (=1/LDR) | Max thinning (typ.) | Draws before anneal |
|---|---|---|---|---|---|---|---|---|---|
| DC04 deep-drawing steel | EN 10130 | annealed | 0.8 | 1.6 | ≈ 2.0 | ≈ 1.75 | ≈ 0.50 | 15–25% | 3 |
| DC06 / IF steel | EN 10130 | annealed | 0.8 | 2.0 | ≈ 2.2 | ≈ 1.91 | ≈ 0.45 | 18–28% | 4 |
| SPCC | JIS G 3141 | annealed | 1.0 | 1.3 | ≈ 1.95 | ≈ 1.70 | ≈ 0.51 | 15–25% | 3 |
| 304 stainless steel | AISI 304 | 2B | 0.8 | 1.0 | ≈ 1.8 | ≈ 1.57 | ≈ 0.56 | 18–30% | 2 |
| 316 stainless steel | AISI 316 | 2B | 1.0 | 1.0 | ≈ 1.75 | ≈ 1.52 | ≈ 0.57 | 18–30% | 2 |
| 430 stainless steel | AISI 430 | 2B | 0.8 | 1.1 | ≈ 1.85 | ≈ 1.61 | ≈ 0.54 | 18–28% | 2 |
| Aluminium 1050-O | GB/T 3880 | O | 1.0 | 0.65 | ≈ 1.75 | ≈ 1.52 | ≈ 0.57 | 12–22% | 3 |
| Aluminium 5052-H32 | GB/T 3880 | H32 | 1.0 | 0.70 | ≈ 1.8 | ≈ 1.57 | ≈ 0.56 | 15–25% | 2 |
| Copper C11000 | GB/T 5231 | annealed | 0.8 | 0.95 | ≈ 1.9 | ≈ 1.65 | ≈ 0.53 | 15–25% | 3 |
| Brass H65 | GB/T 5231 | annealed | 0.8 | 0.90 | ≈ 1.85 | ≈ 1.61 | ≈ 0.54 | 15–25% | 2 |
Reference LDR figures are typical published values for the standard conditions in the test conditions section; they are not a guarantee for any specific shop. Actual limits shift with lubrication, die radii, relative thickness and press behaviour — treat these as the starting point for tool trials. r̄ is the normal plastic anisotropy ratio; m₁ is the first-draw draw coefficient, the reciprocal of LDR.
The four formulas behind every quote
1. Blank diameter (equal-area method)
2. Draw ratio vs. limit
3. Wall thinning
4. Drawing force (press selection)
Three corrections that outweigh the material grade
- Relative thickness (t₀/D_b)×100: at 0.6 or above a smaller draw coefficient can be used; below 0.6 thin blanks wrinkle before they ever reach the tabulated limit, so the usable ratio drops.
- Die entry radius r_die: below 6×t the limit falls; at (7–8)×t it recovers.
- Lubrication: dropping the friction coefficient from 0.15 to 0.05 lifts the achievable LDR by roughly 15–20%.
Multi-draw coefficients and stage planning
What buyers usually need is not “can it be drawn in one hit” but “how many stages, and is an anneal needed” — that is what drives tooling cost and price. Later stages need larger coefficients because work hardening accumulates.
| Material | m₁ (first draw) | m₂ | m₃ | m₄ | Max stages without interstage anneal |
|---|---|---|---|---|---|
| DC04 low-carbon steel | ≈ 0.50–0.55 | 0.75–0.80 | 0.80–0.85 | 0.85–0.90 | 3 |
| DC06 deep-drawing steel | ≈ 0.45–0.50 | 0.73–0.78 | 0.78–0.83 | 0.83–0.88 | 4 |
| 304 stainless steel | ≈ 0.55–0.62 | 0.80–0.87 | 0.85–0.90 | — | 2 |
| 5052 aluminium | ≈ 0.53–0.59 | 0.78–0.83 | 0.82–0.87 | — | 2 |
| C11000 copper | ≈ 0.53–0.59 | 0.78–0.83 | 0.82–0.87 | — | 3 |
Stage coefficients are published industry reference ranges, not shop-measured values. Stainless steel and brass harden fast and need an interstage anneal after about two draws; low-carbon steels hold ductility for three.
Blank diameter and stage estimator
Enter your cup dimensions to get the blank size, total draw ratio, relative thickness and an estimated stage count. Theoretical blank only — your tool engineer should always confirm.
Wall thickness is a gradient, not a number
Along the part height, wall thickness is never constant: the flange thickens as the circumference contracts, and the thinnest point sits above the punch radius. A drawing that calls out a wall thickness without naming the measurement position is the number-one cause of first-article disputes — supplier and customer each measure at a different height, both readings are correct, and they still do not match.
| Position | Typical (mm) | vs t₀ |
|---|---|---|
| Top edge / flange | 0.84 | +5% |
| Above punch radius | 0.66 | −17.5% (thinnest) |
| Mid wall | 0.70 | −12.5% |
| Bottom centre | 0.79 | −1% |
Typical distribution for DC04 at 0.8 mm drawn to Ø40 × 30 mm. Always section and measure your own parts before quoting a wall thickness — and always state on the drawing where it is to be measured.
The test conditions behind the reference values
An LDR number without its test conditions is not data. These are the standard conditions under which the published figures in this industry are produced (GB/T 15825.3-2008 series-diameter blank method):
| Condition | Standard setup |
|---|---|
| Test method | GB/T 15825.3-2008, series-diameter blanks drawn to fracture (Swift cup drawing as cross-check) |
| Failure criterion | visible fracture above the punch nose radius |
| Die entry radius r_die | (7–8) × t₀ |
| Punch nose radius r_p | (3–5) × t₀ |
| Die clearance per side | steel 1.1–1.3×t₀; stainless steel 1.2–1.4×t₀; aluminium 1.0–1.2×t₀ |
| Lubrication | chlorinated-paraffin drawing oil, applied each stage |
| Blank holder force | ≈ 22% of drawing force, held constant |
| Press | hydraulic with die cushion |
| Measurement | ultrasonic thickness gauge, 4 positions, ≥30 samples |
| Re-validation | quarterly, or on any lubricant / tooling change |
Failure modes and what actually fixes them
| Failure | Where it appears | Root cause | Fix |
|---|---|---|---|
| Fracture | thinnest wall above the punch radius | draw ratio over limit, radius too small, blank holder too tight | add a draw stage, enlarge the bottom radius, improve lubrication |
| Wrinkling | flange or upper wall | insufficient BHF, draw bead too loose | raise BHF, tighten the bead |
| Earing | 4, 6 or 8 ears at the cup rim | planar anisotropy Δr | change stock, or allow trim margin |
| Galling | wall surface; common on aluminium and stainless steel | tool finish, lubricant breakdown | polish the die, change lubricant |
| Spring-in | side wall after ejection | elastic recovery in thin walls | light sizing pass, profile compensation |
Material selection cheat sheet
| Material | Formability (ref. LDR) | Corrosion resistance | Relative cost | Surface finish options | Typical deep drawn parts |
|---|---|---|---|---|---|
| SPCC / DC01–DC04 | good (≈ 1.9–2.1) | fair — needs plating or coating | low | zinc plating, painting, phosphating | shallow pans, covers, motor shells |
| DC05 / DC06 | excellent (≈ 2.1–2.3) | fair | medium | same as above | deep cavities, hard deep drawn parts |
| 304 stainless steel | fair (≈ 1.6–2.0, hardens fast) | excellent | medium-high | brushed, electropolished, passivated | food equipment, medical devices |
| 316 stainless steel | fair | excellent (with Mo) | high | same as above | corrosion-resistant vessels, chemical parts |
| 430 stainless steel | fair | good | medium | polishing | magnetic housings, appliance drums |
| 1050 / 3003 aluminium | good | fair | low | anodising, painting | capacitor shells, lamp cups, shades |
| 5052 aluminium | fair-good | good | medium | anodising, chromate conversion | structural parts, electronic enclosures |
| C11000 copper | good | fair | medium-high | nickel / tin plating, passivation | electrical terminals, fittings |
| H62–H68 brass | good | fair | medium | chrome / nickel plating, polishing | cartridge-type parts, decorative parts, bellows |
Selection rule of thumb: for deep cavities, look at r̄ and the n-value before you look at cost. When corrosion resistance and depth are both mandatory, price the extra draw stages and anneals on 316 before committing.
DFM checklist before you release the drawing
The eight checks that resolve most deep drawing problems before tooling starts:
- Bottom radius at least 3–5× sheet thickness — below that, fracture risk climbs steeply.
- Die entry radius at least 7–8× sheet thickness.
- Clearance per side 1.0–1.4× sheet thickness, by material.
- When total draw ratio exceeds the allowable, add a stage — do not push the stroke.
- Wall thickness callouts must name the measurement position (rim / mid wall / above radius).
- Flange width at least 2.5× sheet thickness, leaving room for wrinkling.
- On earing-prone stock, allow 5–10% trim margin.
- Deep cavity plus thin stock (relative thickness below 0.6) — run process simulation before cutting tool steel.
Frequently asked questions
What is a good draw ratio for mild steel in one hit?
Around 2.0 for DC04 with a well-tuned die and a bottom radius of 3–5× sheet thickness. Deep-drawing grades such as DC06 reach higher. Beyond the limit, sequence a second draw rather than pushing the stroke.
Can stainless steel be drawn as easily as mild steel?
No. Austenitic stainless steel work-hardens quickly, so its single-draw limit sits lower than DC04 and an interstage anneal enters the plan after about two draws instead of three.
Why does my drawn cup crack at the bottom corner?
Because that is where the wall is thinnest — the punch nose radius carries the highest local stress. Enlarging the radius to at least 3× material thickness usually recovers more margin than changing the material.
How much wall thinning should I expect?
Plan for 15–22% at the thinnest point on a well-designed draw. Above roughly 25% you are close to the fracture limit. Always state on the drawing where thickness is to be measured.
When is an intermediate anneal required?
When accumulated work hardening leaves too little ductility for the next stage — typically after two draws on 304 stainless steel, three on DC04. It is part of the process plan, not a rescue step.
What is the difference between draw ratio and draw coefficient?
They are reciprocals. LDR = D_b/d_p is greater than 1 — larger means deeper reduction. The draw coefficient m₁ = d₁/D_b is less than 1 — smaller means more deformation per draw. European and US buyers usually speak in LDR; Chinese engineers often use m.
Does relative thickness really change the limit?
Yes, more than most designers expect. When (t₀/D_b)×100 falls below about 0.6, thin blanks wrinkle before they reach the tabulated limit, so the usable ratio drops even though the material is unchanged.
Do you evaluate the draw ratio for my specific part?
Yes. Send the drawing and we will return the calculated blank diameter, draw ratio, stage count and predicted thinning before tooling starts — see our deep drawing capability page.
Send us your drawing
DFM feedback within 24 hours, including the blank diameter, draw ratio, stage count and predicted wall thinning for your part. Tooling samples in 3–4 weeks from PO.
Request a Quote →
Reference data on this page are published typical values under the stated conditions, not shop-measured guarantees. Actual feasibility depends on your specific geometry — send the drawing for an assessment.
Last updated 2026-10-20 · Aunov Tech Co., Ltd., Hangzhou, China
Draw Ratio in Real Parts
The limiting draw ratio is easiest to understand against actual components rather than as an abstract formula. Three parts from our own lines illustrate the range:
- Moderate ratio, one draw. Our steel deep drawn ring cup with notched rim forms comfortably in a single stroke because the depth stays well inside the first-draw limit.
- High aspect ratio, multiple draws. The steel deep drawn long tube with expanded sections needs a full redraw schedule precisely because depth relative to diameter is what consumes the ratio.
- Thin wall, careful control. Our stainless steel 304 thin wall precision tubes sit where wall thinning, not depth, becomes the binding constraint.
When you compare your own part against these, remember that the published limit is a starting point: the usable ratio depends on die geometry, lubrication, material condition and how much wall thinning your specification tolerates. For the practical design consequences, see designing small deep drawn parts.