Reference · H/500, turn-of-nut, RPM, sag
Field calculators
Numbers from the erection guide, on the phone, in the mud. Confirm against the job drawings if they specify something tighter.
Plumb and straight — H/500
Columns plumb to height/500. Beams straight, splices included, to span/500. Girts and purlins straight to L/500.
H/500 · plumb & straight
Columns plumb to height/500. Beams, girts, and purlins straight to span/500.
± L / 500
5⁄8″
Allowable departure from plumb or straight. 300″ of member · 0.600″ decimal.
Guide example: 25 ft → ±⅝″.
Rod sag — L/500
Tighten rod braces so sag is not more than length/500. Example in the guide: 35 ft × 12 / 500 = ±¹³⁄₁₆″.
Rod sag · L/500
Tighten so the rod does not sag more than length/500. Matching rods in a bay get equal tension.
± L / 500
13⁄16″
Maximum sag. 420″ of member · 0.840″ decimal.
Guide example: 35 ft → ±13/16″.
Turn-of-nut
From snug-tight, on flat surfaces. ⅓ turn when L ≤ 4d, ½ turn when 4d < L ≤ 8d, ⅔ turn when 8d < L ≤ 12d. Tolerance ±30° on ⅓ and ½; ±45° on ⅔.
Turn-of-nut
From snug-tight, flat surfaces only.
Required rotation
½ turn
L = 5.3d. Tolerance ±30°. Match-mark nut, bolt, and steel.
Minimum pretension · ¾″ · A325 / F1852 28 kips · A490 35 kips. Calibrate three assemblies of each diameter, length, and grade on a Skidmore.
Screw gun RPM
Screw gun RPM
Variable speed 0–2000. Depth nosepiece. No impact. ≥ 6 amp.
Maximum RPM
2,000 RPM
Total thickness 0.018″ – 0.095″. Steady pressure. Three threads past the substrate. Swarf off the panel.