diff --git a/vitamins/screw.scad b/vitamins/screw.scad
index befca53..7023f53 100644
--- a/vitamins/screw.scad
+++ b/vitamins/screw.scad
@@ -237,21 +237,25 @@ module screw(type, length, hob_point = 0, nylon = false) { //! Draw specified sc
         }
 
         if(head_type == hs_dome) {
-            lift = 0.38;
-            h = head_height - lift;
-            r = min(2 * head_height, (sqr(head_rad) + sqr(h)) / 2 * h); // Special case for M2
-            y = sqrt(sqr(r) - sqr(head_rad));
+            R_minus_h = head_height; // h would be the height of the sphere cap that's cut off of the top of the screw dome
+            a= socket_rad;
+                // this is the trig way to do this, 
+            // alpha=atan(R_minus_h/a);
+            // R = R_minus_h/sin(alpha); //Radius if the cap was a perfect unscaled sphere
+                // this is mathematcially equivalent, but may run faster computationally with sqrt and ^2 instead of trig
+            R= a*sqrt((R_minus_h^2/a^2)+1); // Radius if the cap was a perfect unscaled sphere
+            dome_height_scaling_factor= R/head_rad;
             color(colour) {
                 rotate_extrude() {
                     difference() {
                         intersection() {
-                            translate([0, -y + lift])
-                                circle(r);
+                                scale([1,dome_height_scaling_factor])
+                                circle(r=head_rad);
 
                             square([head_rad, head_height]);
                         }
                         translate([0, head_height - socket_depth])
-                            square([socket_rad, 10]);
+                            square([socket_rad, 20]);
                     }
                 }
                 linear_extrude(head_height)
diff --git a/vitamins/screws.scad b/vitamins/screws.scad
index 152361c..6fd2b7d 100644
--- a/vitamins/screws.scad
+++ b/vitamins/screws.scad
@@ -87,6 +87,8 @@ M2p5_dome_screw  = ["M2p5_dome", "M2.5 dome",   hs_dome,2.5, 5.35,1.6,  0.8, 2.0
 M3_dome_screw    = ["M3_dome", "M3 dome",       hs_dome,  3, 5.7, 1.65, 1.04,2.0, 18,  M3_washer, M3_nut,   M3_tap_radius,    M3_clearance_radius];
 M4_dome_screw    = ["M4_dome", "M4 dome",       hs_dome,  4, 7.6, 2.2,  1.3, 2.5, 20,  M4_washer, M4_nut,   M4_tap_radius,    M4_clearance_radius];
 M5_dome_screw    = ["M5_dome", "M5 dome",       hs_dome,  5, 9.5, 2.75, 1.56,3.0, 22,  M5_washer, M5_nut,   M5_tap_radius,    M5_clearance_radius];
+M6_dome_screw    = ["M6_dome", "M6 dome",       hs_dome,  6, 10.5, 3.3,  2.5,4.0, 24,  M6_washer, M6_nut,   M6_tap_radius,    M6_clearance_radius];
+M8_dome_screw    = ["M8_dome", "M8 dome",       hs_dome,  8, 14,   4.4,  3,5.0, 30,  M8_washer, M8_nut,   M8_tap_radius,    M8_clearance_radius];
 
 M2p5_pan_screw   = ["M2p5_pan", "M2.5 pan",     hs_pan, 2.5, 4.7, 1.7,    0,   0, 0, M2p5_washer, M2p5_nut, M2p5_tap_radius,  M2p5_clearance_radius];
 M3_pan_screw     = ["M3_pan", "M3 pan",         hs_pan,   3, 5.4, 2.0,    0,   0, 0,   M3_washer, M3_nut,   M3_tap_radius,    M3_clearance_radius];
@@ -122,7 +124,7 @@ screw_lists = [
 [ 0,               0,              M3_low_cap_screw],
 [ 0,               0,              M3_shoulder_screw, M4_shoulder_screw],
 [ M2_cs_cap_screw, 0,              M3_cs_cap_screw, M4_cs_cap_screw, M5_cs_cap_screw, M6_cs_cap_screw, M8_cs_cap_screw],
-[ M2_dome_screw,   M2p5_dome_screw,M3_dome_screw,   M4_dome_screw,   M5_dome_screw],
+[ M2_dome_screw,   M2p5_dome_screw,M3_dome_screw,   M4_dome_screw,   M5_dome_screw, M6_dome_screw, M8_dome_screw],
 [ 0,               0,              M3_hex_screw,    M4_hex_screw,    M5_hex_screw,    M6_hex_screw, M8_hex_screw],
 [ 0,               M2p5_pan_screw, M3_pan_screw,    M4_pan_screw,    M5_pan_screw,    M6_pan_screw, No632_pan_screw],
 [ No2_screw,       0,              No4_screw,       No6_screw,       No8_screw,       No6_cs_screw],