Bend Allowance (Flat Length)
Calculate the material length consumed in a bend (bend allowance), BA = (π/180)·θ·(R + K·t), from the bend angle θ (degrees), inner bend radius R (mm), thickness t (mm) and K factor (neutral-line factor, typically 0.33-0.5). This is one of the most important — and subtlest — calculations in sheet metal work: to make a bent part to correct dimensions, you must know the FLAT sheet (blank) size before bending. The catch is that, on bending, the outer face STRETCHES and the inner face COMPRESSES, and there is an intermediate line — the neutral line — that does not change length. The K factor locates that neutral line within the thickness (not exactly in the middle, but shifted inward, so K < 0.5). The total developed length is the sum of the straight flanges plus each bend's allowance. Getting this wrong makes out-of-size parts — a costly production error. So blank development (with K factors calibrated by material and process) is a critical step in sheet-part design, now automated in sheet-metal CAD. Enter the angle, inner radius, thickness and K factor.
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Bend allowance (flat length)
The length of material consumed in a bend (the bend allowance) is BA = (π/180)·θ·(R + K·t), from the bend angle θ, the inside radius R, the thickness t and the K factor (the neutral-line factor, typically 0.33 to 0.5). This is one of the most important — and most subtle — calculations in press work and sheet metal fabrication: to make a bent part with the right finished dimensions, you have to know the size of the flat sheet (the blank) before bending it. The catch is that, during bending, the material on the outer face stretches while the material on the inner face compresses, and in between lies a line — the neutral line — whose length never changes. The K factor locates that neutral line within the thickness (it does not sit exactly in the middle, but shifted inwards, hence K < 0.5). The total developed length of the part is the sum of the straight sections (flanges) plus the bend allowances of each bend. Getting this calculation wrong yields parts that are out of size — a very expensive error in series production, discovered only after hundreds of pieces have been cut and bent. That is why blank development (with K factors calibrated per material and process) is a critical step in designing bent sheet parts, nowadays automated inside sheet metal CAD software. Enter the angle, the inside radius, the K factor and the thickness.
Related Tools
V-Bending Force
Calculate the force to bend a sheet in a V-die, F = (C·σ_r·L·t²) ÷ V, from the process constant C (~1.33 for free V-bending), the material tensile strength σ_r (N/mm²), the bend length L (mm), the sheet thickness t (mm) and the V-die opening V (mm). V-bending is the most common forming operation on press brakes: the sheet rests on a V-shaped die and a punch forces it in, bending it to the desired angle. Force grows with the SQUARE of thickness (thicker sheets need much higher forces) and with material strength, and decreases with die opening (larger V → lower force, but larger bend radius). The rule of thumb uses V ≈ 6-8 times the thickness. Computing the force is essential to select the press brake (tonnage) and not overload the tooling. The bend-tonnage tables ubiquitous in sheet shops are exactly this formula applied to combinations of thickness, material and die opening. Enter the constant, tensile strength, length, thickness and die opening.
Half-Wave Dipole Length
Calculate the physical length of a half-wave dipole, L = (150 ÷ f)·VF, from the frequency f (MHz) and the velocity factor VF (typically ~0.95 for wires, correcting the end effect). The result, in metres, is the total length of the dipole antenna resonant at the desired frequency — each arm is half this value. The half-wave dipole is the most used reference antenna, with 2.15 dBi gain. The velocity factor makes the antenna slightly shorter than a half wavelength in vacuum. Enter the frequency and the velocity factor.
Minimum Bend Radius
Estimate a sheet's minimum bend radius, R_min = t·(50/r − 1), from the thickness t (mm) and the material's percent reduction of area r in the tensile test (%, a ductility measure). The minimum radius is the smallest inner radius you can bend a sheet to WITHOUT cracking the outer face (which is in tension). Bending below the minimum causes cracks or rupture in the outer fiber, where tensile strain exceeds the material's capacity. The minimum radius depends strongly on the material's DUCTILITY (here via reduction of area r): very ductile materials (annealed aluminum, low-carbon steels) can be bent to nearly zero radius (sharp bend), while brittle or work-hardened materials need large radii. It also depends on the bend ORIENTATION relative to the sheet's rolling direction (bending across the rolling direction allows smaller radii than along it, due to anisotropy). Knowing the minimum radius is essential in bent-part design: specifying a smaller radius than possible leads to crack scrap. It is common to express the minimum radius as multiples of thickness (e.g. '2t'). Enter the thickness and the material's reduction of area.
Effective Dose
Compute the effective dose, E = H·wT, multiplying the equivalent dose in an organ (H, in mSv) by the tissue weighting factor (wT) reflecting the tissue's radiosensitivity. While the equivalent dose accounts for the radiation type, the effective dose weights the risk by the irradiated organ (gonads and marrow are more sensitive than skin or bone). It is the quantity used in occupational dose limits. Enter the equivalent dose and the tissue weighting factor.
Structural Safety Factor
Computes the safety factor (FS) as the ratio of resisting load to applied load.
Hardanger Embroidery by Area
Estimates thread for Hardanger embroidery by worked area.
The results provided by this tool are for general informational and educational purposes only and do not constitute professional, financial, medical, legal, tax or accounting advice. Always confirm important decisions with a qualified professional and official sources.