IMPORTANT NOTES REGARDING HEAD MARKINGS:
1) Please see individual photo images for correct head markings.
2) Manufacturing guidelines for Metric sizes: Heads are Knurled and stamped AMPG on all Shoulder Diameters 6mm and larger. Smaller Shoulder Diameters have the AMPG head mark only around the head.
3) Manufacturing guidelines for Inch sizes: Heads are Knurled and stamped AMPG on all Shoulder Diameters 1/4" and larger. Smaller Shoulder Diameters have the AMPG head mark only around the head.
4) The major feature of Knurled versus Smooth heads is the shoulder diameter & length tolerance. The smooth head designated screws have even tighter shoulder tolerances, whereas the Knurled head product range is larger. Since Knurling is purely to provide finger grip, the AMPG head stamp serves this purpose for the smaller Shoulder diameters outlined in (1) and (2) above.
Knurled Head Shoulder Screws are precision made to tight tolerances are suitable for use in machinery and other critical applications. You'll find them used as bearing pins for swing arms, links and levers, as shaft for cam rolls and other rotating part and also as stud bolts.
METRIC tolerances on the shoulder diameter are: -0.010mm to -0.040mm. The shoulder length tolerance is +0.25mm to -0.00mm. Screws with 8, 10, 16 and 20mm shoulder diameters are manufactured to ISO 7379-1983 dimensions. Screws with shoulder diameters of 3, 4, 5, 6 and 12mm are manufactured to AMPG 2013.ZS.02 which also complies with ISO 7379. Metric Knurled Socket Shoulder Screws have a Class 5g6g thread fit.
INCH tolerances on the shoulder diameter are: -0.002" to -0.004" (minus two thousandths to minus four thousandths of an inch). The shoulder length tolerance is +0.005" to -0.005". Screws with 1/4" shoulder diameters upwards are manufactured to meet or exceed ASME B18.3 specifications. Screws with smaller shoulder diameters are manufactured to AMPG 2013.ZS.01. Inch Knurled Socket Shoulder Screws have a Class 3A thread fit.
Type 316 (A4) stainless steel offers more corrosion resistance than 303 (A1/A2/18-8) stainless steel. Widely used in chemical processing and marine enviroments, as the molybdenum in 316 stainless steel has higher resistance to chlorides.