threadlib emancipation

+++++++++++++++++++++++

threadlib is now its own project => remove Waterrocket Fins from this
repo.

threadlib.scad

@@ -0,0 +1,60 @@
+/*
+threadlib
++++++++++
+
+Create threads easily.
+
+:Author: Adrian Schlatter
+:Date: 2019-04-07
+:License: 3-Clause BSD. See LICENSE.
+*/
+
+use <thread_profile.scad>
+include <THREAD_TABLE.scad>
+
+function thread_specs(designator, table=THREAD_TABLE) =
+    /* Returns thread specs of thread-type 'designator' as a vector of
+       [pitch, Rrotation, Dsupport, section_profile] */
+       
+    table[search([designator], table, num_returns_per_match=1,
+                   index_col_num=0)[0]][1];
+
+module thread(designator, turns, higbee_arc=20, fn=120, table=THREAD_TABLE)
+{
+    specs = thread_specs(designator, table=table);
+    P = specs[0]; Rrotation = specs[1]; section_profile = specs[3];
+    straight_thread(
+        section_profile=section_profile,
+        higbee_arc=higbee_arc,
+        r=Rrotation,
+        turns=turns,
+        pitch=P);
+}
+
+module bolt(designator, turns, higbee_arc=20, fn=120, table=THREAD_TABLE) {
+    union() {
+        specs = thread_specs(str(designator, "-ext"), table=table);
+        P = specs[0]; Dsupport = specs[2];
+        H = (turns + 1) * P;
+        thread(str(designator, "-ext"), turns=turns, higbee_arc=higbee_arc, fn=fn, table=table);
+        translate([0, 0, -P / 2])
+            cylinder(h=H, d=Dsupport, $fn=fn);
+    };
+};
+
+module nut(designator, turns, Douter, higbee_arc=20, fn=120, table=THREAD_TABLE) {
+    union() {
+        specs = thread_specs(str(designator, "-int"), table=table);
+        P = specs[0]; Dsupport = specs[2];
+        H = (turns + 1) * P;        
+        rotate(180)
+            thread(str(designator, "-int"), turns=turns, higbee_arc=higbee_arc, fn=fn, table=table);
+
+        translate([0, 0, -P / 2])
+            difference() {
+                cylinder(h=H, d=Douter, $fn=fn);
+                translate([0, 0, -0.1])
+                    cylinder(h=H+0.2, d=Dsupport, $fn=fn);
+            };
+    };
+};