Manufacturing · Sheet metal
Punch and Die Clearance Calculator
Scale radial clearance from stock thickness, size die openings, and estimate shear force — the isometric diagram tracks whichever dimension you are editing.
For catalog materials, clearance % is suggested from alloy family and stock thickness. Choose Custom below to keep a manual value.
Material (for clearance suggestion & punch force)
Punch force uses catalog yield strength with τ ≈ σy/√3 — approximate planning only, not press tonnage certification.
Result
Radial clearance
c = (p/100) × t
Pick a hole shape, enter stock thickness, and watch the diagram highlight each dimension you edit.
Material: AISI 1045 Steel
Tooling preview
Scales to your entered dimensions · orange highlight follows the active field
Radial gap per side, die opening sizes, and shear force — the models this calculator uses.
In sheet punching and stamping, clearance is the gap between the punch (male cutter) and the die opening (female). It is usually stated as radial clearance per side: one-half of the diameter clearance on a round punch pair. Enough clearance lets the fracture shear cleanly through the sheet and avoids galling or tight stripping; too little increases punch wear and breakage risk.
- Radial clearancec = (p / 100) × t
- Round die ØD_die ≈ D + 2c
- Square / rect spanspan_die ≈ span + 2c
- Shear forceF = τ × perimeter × t
- Shear stressτ ≈ σ_y / √3
- Stadium perimeterπW + 2L
where c = radial clearance per side (mm), p = clearance as % of thickness per side, and t = stock thickness (mm).
| Material family | Starting % of t | Notes |
|---|---|---|
| Carbon / alloy steel | 6–7% | General sheet punching |
| Stainless steel | 6–7% | Work-hardens — sharp punches help |
| Aluminum alloys | 7–9% | Softer — slightly more % of t |
| Copper alloys | 7–8% | Galling risk if too tight |
| Thermoplastics | 8–10% | Elastic recovery after strip |
| Fiber composites | 4–6% | Delamination sensitive |
Catalog materials auto-suggest from subcategory and thickness. Confirm with your tooling supplier for production dies.
The results panel approximates blanking force using the shear line length of the nominal punch outline, stock thickness t, and catalog yield strength with τ ≈ σ_y / √3 (von Mises shear yield).
Perimeter rules: round πD; square 4S; rectangle 2(W+H); stadium πW + 2L where L is center-to-center straight length between semicircular ends.
- Outputs are approximations for early tooling layout — not qualified die design.
- Burr height and stripping depend on alignment, sharpness, and lubrication.
- For precision work or unfamiliar materials, confirm with your press shop or supplier.