2 * ISO-standard metric threads, following this specification:
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3 * http://en.wikipedia.org/wiki/ISO_metric_screw_thread
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5 * Copyright 2020 Dan Kirshner - dan_kirshner@yahoo.com
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6 * This program is free software: you can redistribute it and/or modify
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7 * it under the terms of the GNU General Public License as published by
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8 * the Free Software Foundation, either version 3 of the License, or
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9 * (at your option) any later version.
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11 * This program is distributed in the hope that it will be useful,
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12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
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13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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14 * GNU General Public License for more details.
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16 * See <http://www.gnu.org/licenses/>.
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18 * Version 2.4. 2019-07-14 Add test option - do not render threads.
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19 * Version 2.3. 2017-08-31 Default for leadin: 0 (best for internal threads).
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20 * Version 2.2. 2017-01-01 Correction for angle; leadfac option. (Thanks to
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21 * Andrew Allen <a2intl@gmail.com>.)
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22 * Version 2.1. 2016-12-04 Chamfer bottom end (low-z); leadin option.
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23 * Version 2.0. 2016-11-05 Backwards compatibility (earlier OpenSCAD) fixes.
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24 * Version 1.9. 2016-07-03 Option: tapered.
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25 * Version 1.8. 2016-01-08 Option: (non-standard) angle.
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26 * Version 1.7. 2015-11-28 Larger x-increment - for small-diameters.
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27 * Version 1.6. 2015-09-01 Options: square threads, rectangular threads.
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28 * Version 1.5. 2015-06-12 Options: thread_size, groove.
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29 * Version 1.4. 2014-10-17 Use "faces" instead of "triangles" for polyhedron
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30 * Version 1.3. 2013-12-01 Correct loop over turns -- don't have early cut-off
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31 * Version 1.2. 2012-09-09 Use discrete polyhedra rather than linear_extrude ()
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32 * Version 1.1. 2012-09-07 Corrected to right-hand threads!
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38 // metric_thread (diameter=8, pitch=1, length=4);
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41 // metric_thread (diameter=8, pitch=1, length=4, square=true);
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43 // Non-standard: long pitch, same thread size.
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44 //metric_thread (diameter=8, pitch=4, length=4, thread_size=1, groove=true);
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46 // Non-standard: 20 mm diameter, long pitch, square "trough" width 3 mm,
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48 //metric_thread (diameter=20, pitch=8, length=16, square=true, thread_size=6,
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49 // groove=true, rectangle=0.333);
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51 // English: 1/4 x 20.
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52 //english_thread (diameter=1/4, threads_per_inch=20, length=1);
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54 // Tapered. Example -- pipe size 3/4" -- per:
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55 // http://www.engineeringtoolbox.com/npt-national-pipe-taper-threads-d_750.html
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56 // english_thread (diameter=1.05, threads_per_inch=14, length=3/4, taper=1/16);
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58 // Thread for mounting on Rohloff hub.
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60 // cylinder (r=20, h=10, $fn=100);
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62 // metric_thread (diameter=34, pitch=1, length=10, internal=true, n_starts=6);
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66 // ----------------------------------------------------------------------------
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67 function segments (diameter) = min (50, max (ceil (diameter*6), 25));
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70 // ----------------------------------------------------------------------------
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71 // diameter - outside diameter of threads in mm. Default: 8.
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72 // pitch - thread axial "travel" per turn in mm. Default: 1.
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73 // length - overall axial length of thread in mm. Default: 1.
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74 // internal - true = clearances for internal thread (e.g., a nut).
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75 // false = clearances for external thread (e.g., a bolt).
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76 // (Internal threads should be "cut out" from a solid using
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77 // difference ()). Default: false.
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78 // n_starts - Number of thread starts (e.g., DNA, a "double helix," has
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79 // n_starts=2). See wikipedia Screw_thread. Default: 1.
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80 // thread_size - (non-standard) axial width of a single thread "V" - independent
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81 // of pitch. Default: same as pitch.
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82 // groove - (non-standard) true = subtract inverted "V" from cylinder
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83 // (rather thanadd protruding "V" to cylinder). Default: false.
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84 // square - true = square threads (per
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85 // https://en.wikipedia.org/wiki/Square_thread_form). Default:
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87 // rectangle - (non-standard) "Rectangular" thread - ratio depth/(axial) width
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88 // Default: 0 (standard "v" thread).
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89 // angle - (non-standard) angle (deg) of thread side from perpendicular to
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90 // axis (default = standard = 30 degrees).
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91 // taper - diameter change per length (National Pipe Thread/ANSI B1.20.1
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92 // is 1" diameter per 16" length). Taper decreases from 'diameter'
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93 // as z increases. Default: 0 (no taper).
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94 // leadin - 0 (default): no chamfer; 1: chamfer (45 degree) at max-z end;
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95 // 2: chamfer at both ends, 3: chamfer at z=0 end.
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96 // leadfac - scale of leadin chamfer (default: 1.0 = 1/2 thread).
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97 // test - true = do not render threads (just draw "blank" cylinder).
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98 // Default: false (draw threads).
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99 module metric_thread (diameter=8, pitch=1, length=1, internal=false, n_starts=1,
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100 thread_size=-1, groove=false, square=false, rectangle=0,
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101 angle=30, taper=0, leadin=0, leadfac=1.0, test=false)
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103 // thread_size: size of thread "V" different than travel per turn (pitch).
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104 // Default: same as pitch.
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105 local_thread_size = thread_size == -1 ? pitch : thread_size;
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106 local_rectangle = rectangle ? rectangle : 1;
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108 n_segments = segments (diameter);
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109 h = (test && ! internal) ? 0 : (square || rectangle) ? local_thread_size*local_rectangle/2 : local_thread_size / (2 * tan(angle));
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111 h_fac1 = (square || rectangle) ? 0.90 : 0.625;
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113 // External thread includes additional relief.
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114 h_fac2 = (square || rectangle) ? 0.95 : 5.3/8;
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116 tapered_diameter = diameter - length*taper;
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122 metric_thread_turns (diameter, pitch, length, internal, n_starts,
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123 local_thread_size, groove, square, rectangle, angle,
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130 // Solid center, including Dmin truncation.
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132 cylinder (r1=diameter/2, r2=tapered_diameter/2,
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133 h=length, $fn=n_segments);
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134 } else if (internal) {
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135 cylinder (r1=diameter/2 - h*h_fac1, r2=tapered_diameter/2 - h*h_fac1,
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136 h=length, $fn=n_segments);
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139 // External thread.
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140 cylinder (r1=diameter/2 - h*h_fac2, r2=tapered_diameter/2 - h*h_fac2,
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141 h=length, $fn=n_segments);
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146 metric_thread_turns (diameter, pitch, length, internal, n_starts,
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147 local_thread_size, groove, square, rectangle,
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154 // chamfer z=0 end if leadin is 2 or 3
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155 if (leadin == 2 || leadin == 3) {
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157 cylinder (r=diameter/2 + 1, h=h*h_fac1*leadfac, $fn=n_segments);
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159 cylinder (r2=diameter/2, r1=diameter/2 - h*h_fac1*leadfac, h=h*h_fac1*leadfac,
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164 // chamfer z-max end if leadin is 1 or 2.
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165 if (leadin == 1 || leadin == 2) {
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166 translate ([0, 0, length + 0.05 - h*h_fac1*leadfac]) {
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168 cylinder (r=diameter/2 + 1, h=h*h_fac1*leadfac, $fn=n_segments);
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169 cylinder (r1=tapered_diameter/2, r2=tapered_diameter/2 - h*h_fac1*leadfac, h=h*h_fac1*leadfac,
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178 // ----------------------------------------------------------------------------
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179 // Input units in inches.
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180 // Note: units of measure in drawing are mm!
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181 module english_thread (diameter=0.25, threads_per_inch=20, length=1,
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182 internal=false, n_starts=1, thread_size=-1, groove=false,
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183 square=false, rectangle=0, angle=30, taper=0, leadin=0,
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184 leadfac=1.0, test=false)
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187 mm_diameter = diameter*25.4;
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188 mm_pitch = (1.0/threads_per_inch)*25.4;
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189 mm_length = length*25.4;
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191 echo (str ("mm_diameter: ", mm_diameter));
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192 echo (str ("mm_pitch: ", mm_pitch));
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193 echo (str ("mm_length: ", mm_length));
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194 metric_thread (mm_diameter, mm_pitch, mm_length, internal, n_starts,
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195 thread_size, groove, square, rectangle, angle, taper, leadin,
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199 // ----------------------------------------------------------------------------
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200 module metric_thread_turns (diameter, pitch, length, internal, n_starts,
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201 thread_size, groove, square, rectangle, angle,
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204 // Number of turns needed.
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205 n_turns = floor (length/pitch);
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209 // Start one below z = 0. Gives an extra turn at each end.
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210 for (i=[-1*n_starts : n_turns+1]) {
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211 translate ([0, 0, i*pitch]) {
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212 metric_thread_turn (diameter, pitch, internal, n_starts,
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213 thread_size, groove, square, rectangle, angle,
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219 translate ([0, 0, length/2]) {
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220 cube ([diameter*3, diameter*3, length], center=true);
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226 // ----------------------------------------------------------------------------
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227 module metric_thread_turn (diameter, pitch, internal, n_starts, thread_size,
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228 groove, square, rectangle, angle, taper, z)
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230 n_segments = segments (diameter);
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231 fraction_circle = 1.0/n_segments;
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232 for (i=[0 : n_segments-1]) {
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233 rotate ([0, 0, i*360*fraction_circle]) {
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234 translate ([0, 0, i*n_starts*pitch*fraction_circle]) {
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235 //current_diameter = diameter - taper*(z + i*n_starts*pitch*fraction_circle);
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236 thread_polyhedron ((diameter - taper*(z + i*n_starts*pitch*fraction_circle))/2,
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237 pitch, internal, n_starts, thread_size, groove,
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238 square, rectangle, angle);
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245 // ----------------------------------------------------------------------------
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246 module thread_polyhedron (radius, pitch, internal, n_starts, thread_size,
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247 groove, square, rectangle, angle)
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249 n_segments = segments (radius*2);
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250 fraction_circle = 1.0/n_segments;
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252 local_rectangle = rectangle ? rectangle : 1;
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254 h = (square || rectangle) ? thread_size*local_rectangle/2 : thread_size / (2 * tan(angle));
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255 outer_r = radius + (internal ? h/20 : 0); // Adds internal relief.
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256 //echo (str ("outer_r: ", outer_r));
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258 // A little extra on square thread -- make sure overlaps cylinder.
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259 h_fac1 = (square || rectangle) ? 1.1 : 0.875;
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260 inner_r = radius - h*h_fac1; // Does NOT do Dmin_truncation - do later with
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263 translate_y = groove ? outer_r + inner_r : 0;
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264 reflect_x = groove ? 1 : 0;
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266 // Make these just slightly bigger (keep in proportion) so polyhedra will
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268 x_incr_outer = (! groove ? outer_r : inner_r) * fraction_circle * 2 * PI * 1.02;
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269 x_incr_inner = (! groove ? inner_r : outer_r) * fraction_circle * 2 * PI * 1.02;
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270 z_incr = n_starts * pitch * fraction_circle * 1.005;
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273 (angles x0 and x3 inner are actually 60 deg)
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275 /\ (x2_inner, z2_inner) [2]
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277 (x3_inner, z3_inner) / \
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279 |\ \ (x2_outer, z2_outer) [6]
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282 z |[7]\/ / (x1_outer, z1_outer) [5]
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285 | / | / (x0_outer, z0_outer) [4]
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286 | / | / (behind: (x1_inner, z1_inner) [1]
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289 (r) / (x0_inner, z0_inner) [0]
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293 x1_outer = outer_r * fraction_circle * 2 * PI;
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295 z0_outer = (outer_r - inner_r) * tan(angle);
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296 //echo (str ("z0_outer: ", z0_outer));
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298 //polygon ([[inner_r, 0], [outer_r, z0_outer],
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299 // [outer_r, 0.5*pitch], [inner_r, 0.5*pitch]]);
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300 z1_outer = z0_outer + z_incr;
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302 // Give internal square threads some clearance in the z direction, too.
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303 bottom = internal ? 0.235 : 0.25;
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304 top = internal ? 0.765 : 0.75;
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306 translate ([0, translate_y, 0]) {
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307 mirror ([reflect_x, 0, 0]) {
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309 if (square || rectangle) {
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311 // Rule for face ordering: look at polyhedron from outside: points must
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312 // be in clockwise order.
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315 [-x_incr_inner/2, -inner_r, bottom*thread_size], // [0]
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316 [x_incr_inner/2, -inner_r, bottom*thread_size + z_incr], // [1]
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317 [x_incr_inner/2, -inner_r, top*thread_size + z_incr], // [2]
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318 [-x_incr_inner/2, -inner_r, top*thread_size], // [3]
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320 [-x_incr_outer/2, -outer_r, bottom*thread_size], // [4]
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321 [x_incr_outer/2, -outer_r, bottom*thread_size + z_incr], // [5]
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322 [x_incr_outer/2, -outer_r, top*thread_size + z_incr], // [6]
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323 [-x_incr_outer/2, -outer_r, top*thread_size] // [7]
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327 [0, 3, 7, 4], // This-side trapezoid
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329 [1, 5, 6, 2], // Back-side trapezoid
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331 [0, 1, 2, 3], // Inner rectangle
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333 [4, 7, 6, 5], // Outer rectangle
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335 // These are not planar, so do with separate triangles.
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336 [7, 2, 6], // Upper rectangle, bottom
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337 [7, 3, 2], // Upper rectangle, top
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339 [0, 5, 1], // Lower rectangle, bottom
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340 [0, 4, 5] // Lower rectangle, top
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345 // Rule for face ordering: look at polyhedron from outside: points must
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346 // be in clockwise order.
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349 [-x_incr_inner/2, -inner_r, 0], // [0]
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350 [x_incr_inner/2, -inner_r, z_incr], // [1]
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351 [x_incr_inner/2, -inner_r, thread_size + z_incr], // [2]
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352 [-x_incr_inner/2, -inner_r, thread_size], // [3]
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354 [-x_incr_outer/2, -outer_r, z0_outer], // [4]
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355 [x_incr_outer/2, -outer_r, z0_outer + z_incr], // [5]
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356 [x_incr_outer/2, -outer_r, thread_size - z0_outer + z_incr], // [6]
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357 [-x_incr_outer/2, -outer_r, thread_size - z0_outer] // [7]
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361 [0, 3, 7, 4], // This-side trapezoid
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363 [1, 5, 6, 2], // Back-side trapezoid
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365 [0, 1, 2, 3], // Inner rectangle
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367 [4, 7, 6, 5], // Outer rectangle
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369 // These are not planar, so do with separate triangles.
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370 [7, 2, 6], // Upper rectangle, bottom
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371 [7, 3, 2], // Upper rectangle, top
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373 [0, 5, 1], // Lower rectangle, bottom
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374 [0, 4, 5] // Lower rectangle, top
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