Compare the sum of finished leg dimensions with the centerline path through a bend. The difference is shown as a geometric deduction, helping fabrication planners understand where cut-length adjustments come from.
Enter the finished-leg geometry.
If two finished straight legs are dimensioned to the theoretical intersection of their centerlines, simply adding the finished dimensions can overstate the material needed because the bend follows an arc instead of continuing through the sharp corner. A geometric bend deduction can therefore be expressed as the difference between the straight-leg total and the centerline path associated with the actual bend geometry.
Real reinforcing-bar schedules may define dimensions to tangent points, outside faces, inside faces or other reference locations. Bend diameters and fabrication tolerances also matter. Consequently, the geometric deduction shown here is a transparent calculation model, not a universal shop-floor deduction table.
With two finished legs of 500 and 300 mm, a 90° bend and an 80 mm centerline radius, the centerline arc is 125.66 mm. The corresponding geometric path model is compared with the 800 mm straight-leg total, producing the displayed deduction.
No. Allowance describes the curved portion of a bend; deduction is a cut-length accounting concept.
Only when its dimension convention matches the project fabrication standard. Otherwise it is a geometry check.
It makes the geometric calculation unambiguous and avoids silently mixing inside and centerline measurements.