From 88b5c4ce215a6e537b46e541224219b8375930d6 Mon Sep 17 00:00:00 2001
From: Ian Jackson <ijackson@chiark.greenend.org.uk>
Date: Sun, 10 May 2020 15:33:51 +0100
Subject: [PATCH] threads: download v2.5

https://www.dkprojects.net/openscad-threads/

Signed-off-by: Ian Jackson <ijackson@chiark.greenend.org.uk>
---
 threads.scad | 49 +++++++++++++++++++++++++++++++++++++------------
 1 file changed, 37 insertions(+), 12 deletions(-)

diff --git a/threads.scad b/threads.scad
index c958cb5..b2eee23 100644
--- a/threads.scad
+++ b/threads.scad
@@ -15,6 +15,7 @@
  *
  * See <http://www.gnu.org/licenses/>.
  *
+ * Version 2.5.  2020-04-11  Leadin option works for internal threads.
  * Version 2.4.  2019-07-14  Add test option - do not render threads.
  * Version 2.3.  2017-08-31  Default for leadin: 0 (best for internal threads).
  * Version 2.2.  2017-01-01  Correction for angle; leadfac option.  (Thanks to
@@ -93,7 +94,7 @@ function segments (diameter) = min (50, max (ceil (diameter*6), 25));
 //               as z increases.  Default: 0 (no taper).
 // leadin      - 0 (default): no chamfer; 1: chamfer (45 degree) at max-z end;
 //               2: chamfer at both ends, 3: chamfer at z=0 end.
-// leadfac     - scale of leadin chamfer (default: 1.0 = 1/2 thread).
+// leadfac     - scale of leadin chamfer length (default: 1.0 = 1/2 thread).
 // test        - true = do not render threads (just draw "blank" cylinder).
 //               Default: false (draw threads).
 module metric_thread (diameter=8, pitch=1, length=1, internal=false, n_starts=1,
@@ -149,27 +150,50 @@ module metric_thread (diameter=8, pitch=1, length=1, internal=false, n_starts=1,
                }
             }
          }
-      }
 
-      // chamfer z=0 end if leadin is 2 or 3
-      if (leadin == 2 || leadin == 3) {
-         difference () {
-            cylinder (r=diameter/2 + 1, h=h*h_fac1*leadfac, $fn=n_segments);
+         // Internal thread lead-in: take away from external solid.
+         if (internal) {
+
+            // "Negative chamfer" z=0 end if leadin is 2 or 3.
+            if (leadin == 2 || leadin == 3) {
+               cylinder (r1=diameter/2, r2=diameter/2 - h*h_fac1*leadfac, h=h*h_fac1*leadfac,
+                         $fn=n_segments);
+            }
 
-            cylinder (r2=diameter/2, r1=diameter/2 - h*h_fac1*leadfac, h=h*h_fac1*leadfac,
-                      $fn=n_segments);
+            // "Negative chamfer" z-max end if leadin is 1 or 2.
+            if (leadin == 1 || leadin == 2) {
+               translate ([0, 0, length + 0.05 - h*h_fac1*leadfac]) {
+                  cylinder (r1=tapered_diameter/2 - h*h_fac1*leadfac, h=h*h_fac1*leadfac,
+                            r2=tapered_diameter/2,
+                            $fn=n_segments);
+               }
+            }
          }
       }
 
-      // chamfer z-max end if leadin is 1 or 2.
-      if (leadin == 1 || leadin == 2) {
-         translate ([0, 0, length + 0.05 - h*h_fac1*leadfac]) {
+      if (! internal) {
+
+         // Chamfer z=0 end if leadin is 2 or 3.
+         if (leadin == 2 || leadin == 3) {
             difference () {
                cylinder (r=diameter/2 + 1, h=h*h_fac1*leadfac, $fn=n_segments);
-               cylinder (r1=tapered_diameter/2, r2=tapered_diameter/2 - h*h_fac1*leadfac, h=h*h_fac1*leadfac,
+
+               cylinder (r2=diameter/2, r1=diameter/2 - h*h_fac1*leadfac, h=h*h_fac1*leadfac,
                          $fn=n_segments);
             }
          }
+
+         // Chamfer z-max end if leadin is 1 or 2.
+         if (leadin == 1 || leadin == 2) {
+            translate ([0, 0, length + 0.05 - h*h_fac1*leadfac]) {
+               difference () {
+                  cylinder (r=diameter/2 + 1, h=h*h_fac1*leadfac, $fn=n_segments);
+
+                  cylinder (r1=tapered_diameter/2, r2=tapered_diameter/2 - h*h_fac1*leadfac, h=h*h_fac1*leadfac,
+                            $fn=n_segments);
+               }
+            }
+         }
       }
    }
 }
@@ -380,3 +404,4 @@ module thread_polyhedron (radius, pitch, internal, n_starts, thread_size,
 }
 
 
+
-- 
2.30.2