DZUS FASTENER 12.7mm & S5 SPRING
DZUS Fasteners is a type of proprietary quarter-turn lock fastener that is often used to secure skin panels on aircraft and other high-performance vehicles. Turnlock fasteners are also referred to as quick-action panel fasteners.
The EHF5 has a 37mm head with 27mm between the rivet holes, is 1.47" long, 7/8" wide and uses S5 springs.
The EHF6 has a 44mm head with 34mm between the rivet holes, is 1.725" long, 1 3/32" wide and uses S6 springs.
To calculate the correct pairing of fastener and spring us the following formula: Add together the thicknesses of both panels to be fastened and the spring clearance. Subtract spring deflection (0.047" for EHF5 and 0.062" for EHF6). Then select the fastener with the nearest shaft length.