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100 lines
3.1 KiB
OpenSCAD
100 lines
3.1 KiB
OpenSCAD
/*
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Britisch Standard Pipe Thread
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++++++++++++++++++++++++++++++
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British Standard Pipe Thread is based on a triangular profile. The angle between flanks
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is 55 deg (symmetrical). We use the following nomenclature:
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- crest: The "summit" of a thread
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- valley: The lowest point in the valley of a thread
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- rcrest, rvalley: Radii of crest and groove, respectively
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- rpitch = the mean radius of the original triangular profile
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The crest and groove are both truncated by t/6. The radii at these flats are called
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rmajor and rminor.
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Note 1:
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The specification requires that the flats are smoothed by circles that tangentially
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match the flanks. We use a simpler version here: We create a triangular profile
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and truncate the crests but not the grooves.
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Note 2:
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The specification requires allowances. This module creates threads with the ideal
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rpitch for both external and internal threads (i.e., they just touch each other).
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This is exactly at the edges of the given allowances and will not reliably work
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in practice!
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*/
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use <thread_profile.scad>
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module BSPP_external_thread(pitch=2.309, turns=3, dpitch=31.68, higbee_arc=45, fn=120)
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{
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rpitchp = dpitch / 2;
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P = pitch;
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rcrest = rpitchp + 0.21706 * P;
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rvalley = rpitchp - 0.42021 * P;
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zvalley = 0.03125 * P;
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zcrest = 0.13701 * P;
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section_profile = [[rvalley, -P / 2 + zvalley], [rvalley, +P / 2 - zvalley],
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[rcrest, +zcrest],
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[rcrest, -zcrest]];
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straight_thread(
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section_profile=section_profile,
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higbee_arc=higbee_arc,
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r=0,
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turns=turns,
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pitch=pitch,
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fn=fn);
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}
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module BSPP_internal_thread(pitch=2.309, turns=3, dpitch=31.86, higbee_arc=45, fn=120)
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{
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rpitchp = dpitch / 2;
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P = pitch;
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rcrest = rpitchp - 0.19813 * P;
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rvalley = rpitchp + 0.42021 * P;
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zvalley = 0.03125 * P;
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zcrest = 0.13701 * P;
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section_profile = [[rvalley, P / 2 - zvalley], [rvalley, -P / 2 + zvalley],
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[rcrest, -zcrest], [rcrest, +zcrest]];
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rotate(180) // rotate by half a turn to fit external thread
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straight_thread(
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section_profile=section_profile,
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higbee_arc=higbee_arc,
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r=0,
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turns=turns,
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pitch=pitch,
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fn=fn);
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}
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// testing:
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intersection() {
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color("Green")
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translate([-50, 0, -50])
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cube(100, 100, 100);
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union() {
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BSPP_external_thread(pitch=2.309, turns=3, dpitch=31.68,
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higbee_arc=20, fn=120);
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translate([0, 0, -1.2])
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cylinder(h=9, r=31.68/2 - 0.40020 * 2.309);
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BSPP_internal_thread(pitch=2.309, turns=3, dpitch=31.86,
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higbee_arc=20, fn=120);
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translate([0, 0, -0.9])
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difference() {
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cylinder(h=9, r=20, $fn=120);
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translate([0, 0, -0.1])
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cylinder(h=10, r=31.86/2 + 0.40020 * 2.309, $fn=120);
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};
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};
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};
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