metric-socket-cap.md

title	date
How To Design 3d Printer Parts for Mechanical Fasteners	24 Aug 2019

Dimensions for Self Tapping Screws

• M3: 2.5mm (tight) or 2.75mm hole
  • using M3x12mm on a 2mm thick surface
  • repeated removal loosens them up ... so 2.5mm might be best over time

3d Printer Dimensions for Fasteners [mm]

Type	Screw Dia. (D)	Print Dia.	Socket Cap Dia. (A)	Socket Cap Depth (H)	Nut Width (E)	Nut Depth (M)
M2	2	2.2	4	2	4.65	1.7
M3	3	3.3	6	3	6.4	2.5
M4	4	4.3	7.5	4	8.1	3.3
M5	5	5.3	9	5	9.3	4.8

• Ita Fasteners

OpenScad Code for Fasteners

// https://www.engineersedge.com/hardware/standard_metric_hex_nuts_13728.htm
// m2: d=4    D=4.62
// m3: d=5.5  D=6.35
module hex(D,t){
    // D is outter diameter
    x = D/2;
    y = sqrt(3)/2*x;
    pts = [
        [x/2,y],
        [x,0],
        [x/2,-y],
        [-x/2,-y],
        [-x,0],
        [-x/2,y]
    ];
    linear_extrude(height=t){
        polygon(pts);
    }
}

module M3Nut(t){
    hex(6.4, t);
}

module M2Nut(t){
    hex(4.65, t);
}

module M2(t){
    cylinder(3*t, d=2.2, center=true);
    translate([0,0,-1]) M2Nut(3); // nut
}

module M3(t){
    cylinder(h=3*t, d=3.3, center=true);
    translate([0,0,2]) cylinder(h=3*t, d=7, center=false); // head
}

Imperial Standard to Metric Conversion

Guage	Decimal	Metric
0	0.060"	1.524 mm
1	0.073"	1.854 mm
2	0.086"	2.180 mm
3	0.099"	2.515 mm
4	0.112"	2.845 mm
5	0.125"	3.175 mm
6	0.138"	3.505 mm
8	0.164"	4.166 mm

References

• metric socket cap screws
• metric nuts