+module CameraMountThread(l){
+ rotate([0,180,0])
+ english_thread(diameter=negative_dia/inch,
+ threads_per_inch=negative_tpi,
+ leadin=0, internal=true, test=$test,
+ length= (l + inch/19) / inch);
+ hull(){
+ translate([0,0, negative_chamfer])
+ cylinder(r= negative_dia/2 + negative_chamfer*2,
+ h=1);
+ mirror([0,0,1])
+ cylinder(r= negative_dia/2 - negative_chamfer*2,
+ h= negative_chamfer*3);
+ }
+}