Hobson technical document
UNC Hex Bolt Properties: SAE Grade 2, 5 and 8 Proof and Tensile Loads
Hobson's four-page technical data sheet of imperial UNC hex bolt properties, in pounds. For each size from 1/4 inch to 2-1/4 inch it lists threads per inch and stress area, with the minimum proof stress, tensile stress, proof load and ultimate tensile load for grade 2, 5 and 8 bolts.
What this covers
- Minimum stress under proof load
- Minimum tensile stress
- Minimum proof load
- Minimum ultimate tensile load
Key things to remember
The essentials from this document in plain words. Check the full document before you rely on a figure.
- Covers 1/4 inch (20 TPI) to 2-1/4 inch (4.5 TPI). Figures for 1-3/4, 2 and 2-1/4 inch are marked as extrapolated.
- Minimum tensile stress: grade 2 74,000 psi up to 3/4 inch and 60,000 psi from 7/8 inch; grade 5 120,000 psi up to 1 inch and 105,000 psi from 1-1/8 inch; grade 8 150,000 psi.
- Minimum proof stress: grade 2 55,000 psi up to 3/4 inch and 33,000 psi from 7/8 inch; grade 5 85,000 psi up to 1 inch and 74,000 psi above; grade 8 120,000 psi.
- 1/2 inch: minimum proof load 7,805 lbf (grade 2), 12,062 lbf (grade 5), 17,028 lbf (grade 8); minimum ultimate tensile load 10,501, 17,028 and 21,285 lbf.
- 3/4 inch: minimum proof load 18,370, 28,390 and 40,080 lbf; minimum ultimate tensile load 24,716, 40,080 and 50,100 lbf.
- These are minimum material properties, not working loads for a joint.
Who it helps: Engineers and staff working with imperial (UNC) bolts.
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This document is published by Hobson Engineering, who supply this range to us. We show it here in full so you can read it next to the product; the summary above is ours. Read it on this page or download the PDF. For the most current version, ask us.