14-05-2018, 05:27 PM
If using Unified threaded bolts "R" are similar to Metric 4.8 and are often called "high tensile" by the unscrupulous
"S" quality are close to metric 8.8
"U" are rare & similar to metric 12.9 and are often seen as cap screws, but again "gang warily" ...look for genuine Unbrako or similar "proper" brands.
You can check the manufacturer of reputable threaded fasteners by looking up the head marking letters (bit of a faff, but the magic of the internet comes to your aid. They should have proper international quality assurance even if based in strange countries!
"S" quality are close to metric 8.8
"U" are rare & similar to metric 12.9 and are often seen as cap screws, but again "gang warily" ...look for genuine Unbrako or similar "proper" brands.
You can check the manufacturer of reputable threaded fasteners by looking up the head marking letters (bit of a faff, but the magic of the internet comes to your aid. They should have proper international quality assurance even if based in strange countries!