Direct Fastening Technical Guide , Edition 24 h NVS well above optimal range *
Piston mark ( indentation ) not visible on fastener Gap visible between washers
Washers not clamping deck sheet to base steel
Figure 12a : Under driven X-ENP-19 fastener with single sheet to base steel . h NVS within optimal range *
Piston mark ( indentation ) clearly visible on fastener
Washers snug against one another and clamping deck sheet to base steel
Figure 12b : Properly driven X-ENP-19 fastener with single sheet to base steel h NVS well below optimal range *
Washers cutting into deck sheet , deforming base steel and deck sheet
Figure 12c : Over driven X-ENP-19 fastener with single sheet to base steel
* Optimal stand-off ( h NVS ) range for the X-ENP-19 fastener is 8.2 mm ≤ h NVS
≤ 9.8 mm .
157