Sheet Metal Calculators

Sheet metal calculators answer two fabrication questions: how long is the flat blank before bending, and is the inside radius safe for this thickness and alloy. Bend allowance and K-factor locate the neutral axis through the bend zone. Minimum bend radius screens crack risk on the outside fiber.

Bend Allowance Calculator develops flat length from angle, inside radius, thickness, and K. Minimum Bend Radius Calculator compares your radius to material-specific ratios for common stock.

Louver and stiffening rib bends consume extra flat length beside the primary profile. Add each bend zone explicitly when the flat ships to laser as one nest outline.

Short flat length wastes a laser nest or leaves the brake operator short on the second bend. Tight radius cracks stainless and zinc coat on the outer surface. Quotes are built on blank perimeter, so development length feeds margin directly.

Designers release bracket prints before the shop proves K on first article. Programmers reconcile CAD unfold with brake reality. Apprentices learn that 1 mm radius on 4 mm plate is a different conversation than on 1 mm aluminum.

Coining and bottoming use a different K table than air bending on the same brake. Document which process the flat length assumes in the traveler.

Hems and safe edges add forming steps after primary bends. Each step needs its own allowance line in the flat, not one K copied from the wall bend alone.

Perforated and expanded metal needs larger radius than solid sheet at the same gauge. Handbook minimums often understate crack risk on open patterns.

Architectural panel subs mix brake trim with field weld shrink. Flat length on trim and installed opening tolerance are separate checks on one elevation.

Powder coat build-up changes effective minimum radius on cosmetic exterior panels. Coupon bends on coated scrap beat handbook ratios when appearance is critical.

• Flat pattern for a multi-bend bracket
• K-factor against shop tables after first article
• Inside radius feasibility on stainless or CRS
• Blank size for laser nest and quote

Bend allowance is (π/180) × angle × (inside radius + K × thickness). K shifts the neutral axis between inner and outer surface as a fraction of thickness. Minimum radius tools compare your callout to handbook or shop ratios by material class.

Angle is usually included angle. Radius is inside unless the form says centerline. Multi-bend parts sum allowance per bend plus straight tangents between zones.

Hemming and joggles add straight tangent length between bend zones. Offset bends on enclosure doors often carry tighter radius limits than a single 90° wall bend.

Laser kerf and bend relief slots change flat length slightly. Programmers add relief before the allowance sum when the CAD model already shows notches.

Springback changes final angle after punch release. High-strength grades and acute bends may need overbend that a simple allowance line does not capture without a test coupon.

• Inside radius and thickness from the print
• Shop K first, refine after coupon bend
• Compare developed length to CAD unfold
• Radius check before releasing tight callouts

Use during bracket layout, fab quotes, and brake program checks. They fit design and programming before long setups or hard tooling.

Grain direction, perforated sheet, and clad products need test coupons beyond handbook minimums. Minimum radius output is a screen, not a guarantee on every lot.

Coining and bottoming change the effective inside radius versus air bend. Shops document a different K table when they move from air to bottoming on the same brake.

Contract fab often receives STEP unfold that ignores shop K. Compare calculator flat length to the customer model, then settle disputes with a coupon from your brake.

Powder coat build-up changes effective minimum radius on cosmetic exterior panels. Coupon bends on coated scrap beat handbook ratios when appearance is critical on the part.

Laser and punch programming on the flat blank is in Machining & CNC Calculators. Position tolerance on formed hole patterns is under GD&T & Metrology Calculators.

Sum allowance on every bend line in the quote, not one average K across the part. Hole pattern tolerance after forming may need stack-up in Fixture & Tooling once flat length is fixed.

• Enclosure and bracket layout
• Press brake program verification
• Fab shop quoting
• Not for final springback without test bends

Most jobs here are layout and feasibility, not theory.

• Box wall flat length with two 90° bends
• K update after first article versus CAD unfold
• 2 mm inside radius on 3 mm stainless screening
• Blank perimeter for sheet nest utilization

Carry the right output into CAD or the brake control. Developed length feeds laser nest files. Minimum radius feeds design review before tight callouts hit the shop floor.

• Bend allowance: arc length added per bend
• Developed length: straights plus all allowances
• Minimum radius: suggested inside limit for material class
• Flat size: input to nest and quote margin
• K-factor: shop-specific constant, not a universal material property