mirror of
https://github.com/bherbruck/solidcraft.git
synced 2026-11-07 12:31:56 +00:00
bherbruck
481687fff3
* Modeled threads: run down to a flat shoulder so a nut can bottom out An external thread running the whole face stopped with its groove clear of a shoulder, leaving up to a turn uncut above it. The groove now runs on past the plane of the face's end and is trimmed there, so its root reaches the shoulder at every angle and nothing past the plane is cut. A shoulder rising back along the face keeps the square stop, as do internal threads, tapers, runouts and lengths stopping short. Where the kernel refuses the trimmed cut, the groove also keeps the square stop and the feature warns. Closes #11610 Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> * Kernel ladder: record the thread cases that now reach their shoulder Six cases gain the faces of the trimmed last turn; every other case is unchanged apart from its timing. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> * Thread at a shoulder: review fixes, and a test of the fallback The shoulder check starts just off the face, as the free-end check does, so a slope rising from the face counts. A groove the trim leaves nothing of now falls back to the square stop too. A test forces the fallback and reads its warning. The ladder's order and report go back to main's, changed only for the cases this moved. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> * Thread at a shoulder: check all the radii the groove cuts The check for a shoulder rising along the face looked a fixed distance out, which falls short of the groove on an undersized shaft. It now covers the groove's reach. A test reads how each kind of shoulder is classified. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> * Thread at a shoulder: test the trim that leaves nothing of the groove The test now reaches the path where the half-space keeps nothing, which is the one that must fall back to the square stop. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> * Thread at a shoulder: say so when the shoulder can't be checked If the kernel can't make the rising-shoulder check, the groove keeps the square stop as before, and the feature now warns that its last turn is left uncut. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> --------- Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>
164 lines
13 KiB
Markdown
164 lines
13 KiB
Markdown
# Threads
|
||
|
||
`solid.thread` puts a thread on a cylindrical face: cosmetic (an annotation, `model.threads`
|
||
lists it) or modelled (the groove between the teeth cut into the body along a helix, SMLib's exact
|
||
screw sweep). This page gives the forms, the values each uses and where they come from, and how a
|
||
thread's extent is decided. The code is `crates/doc/src/thread_forms.rs` (forms, sizes,
|
||
designations) and `crates/doc/src/eval_thread.rs` (the thread on its face, the cut).
|
||
|
||
## Forms
|
||
|
||
Every groove is a polygon in an axial half-plane: straight flanks, flat crest and root. Crest and
|
||
root radii (the ISO metric root radius, the buttress root radius R, DIN 405 knuckle and Whitworth
|
||
rounds) are not modelled. External threads are cut from the shaft's surface (a little past it, so
|
||
no skin is left) down to the external thread's minor diameter; internal threads from the hole
|
||
wall out to the internal thread's root. Pitch-diameter allowances and tolerance classes are not
|
||
modelled: a modelled thread is the maximum-material design profile below.
|
||
|
||
| Form | `form` | Designation | Flanks | Depth | Crest flat | External minor | Internal minor, root |
|
||
|---|---|---|---|---|---|---|---|
|
||
| ISO metric | `metric` | `M10`, `M10x1`, `M16xPh3P1.5` | 30° / 30° | 5H/8, H = P √3/2 | P/8 at d, P/4 at D1 | d − 5H/4 | D1 = d − 5H/4, D = d |
|
||
| Trapezoidal | `trapezoidal` | `Tr20x4`, `Tr40x14(P7)` | 15° / 15° | H1 = P/2 | P/2 (1 − tan 15°) = 0.366 P | d3 = d − 2 (H1 + ac) | D1 = d − P, D4 = d + 2 ac |
|
||
| Acme (general purpose) | `acme` | `1/2-10 ACME` | 14.5° / 14.5° | h = P/2 | P/2 (1 − tan 14.5°) = 0.3707 P | d − P − 0.020″ (0.010″ finer than 10 tpi) | D − P, D + 0.020″ (0.010″) |
|
||
| Metric buttress | `buttress` | `S20x4`, `S40x14(P7)` | 3° (load) / 30° | H1 = 0.75 P | (P − 0.75 P (tan 3° + tan 30°))/2 = 0.26384 P | d3 = d − 2 × 0.86777 P | D1 = d − 1.5 P, D = d |
|
||
| Buttress inch | `buttress_asme` | `2.5-8 BUTT` | 7° (load) / 45° | h = 0.6 P | (P − 0.6 P (tan 7° + 1))/2 = 0.16316 P | d − 1.2 P (basic) | d − 1.2 P, d (basic) |
|
||
|
||
| Parallel pipe | `bspp` | `G 1/2` | 27.5° / 27.5° | h = 0.640327 P of H = 0.960491 P | (H − h) tan 27.5° = 0.1667 P, both | d − 2h | d − 2h, d |
|
||
| Parallel internal (ISO 7-1) | `rp` | `Rp 1/2` | 27.5° / 27.5° | h = 0.640327 P of H = 0.960491 P | (H − h) tan 27.5° = 0.1667 P, both | (internal only) | d − 2h, d |
|
||
| Taper pipe (ISO 7-1) | `bspt` | `R 1/2`, `Rc 1/2` | 27.5° / 27.5° | h = 0.640327 P of H = 0.960237 P | (H − h) tan 27.5°, both | d − 2h at the gauge plane | d − 2h, d at the gauge plane |
|
||
| NPT | `npt` | `1/2-14 NPT` | 30° / 30° | h = 0.8 P of H = 0.866025 P | (H − h) tan 30° = 0.038 P, both | E − h at the plane of E | E − h, E + h |
|
||
|
||
The pipe threads' crest and root rounds (ISO 228-1/7-1 r = 0.137329 P, 0.137278 P taper) are
|
||
modelled as flats at the basic height, as the other forms' radii; NPT takes the minimum truncation
|
||
0.033 P at both. The flanks' bisector is square to the axis in all three.
|
||
|
||
**Taper pipe threads** (`bspt`, `npt`): the diameters change 1 in 16 along the axis. The thread
|
||
starts at a free end, the pipe's end or the hole's mouth (`from`), with the diameter its standard
|
||
puts there: an external thread its major diameter at the gauge (reference) plane its gauge length
|
||
in from the small end (ISO 7-1: the basic gauge length, R 1/2 20.955 mm at 8.2 mm; NPT: E1 + h at
|
||
the hand-tight length L1, E1 = E0 + L1/16), an internal one the reference diameter at its face
|
||
(ISO 7-1's gauge plane; NPT's E1 at the large end). The groove is SMLib's screw sweep with its
|
||
section moved 1/32 of the axial travel off the axis per unit length (the radial law that also
|
||
makes runouts), its walls within the sweep's tolerance of the true surfaces; its section reaches
|
||
just past the crest, and the material beyond the major cone (external) or inside the minor cone
|
||
(internal) is cut with it, as the die or tap cuts the crests. Past the major cone the crests
|
||
vanish into the pipe's surface (ISO 7-1's incomplete thread). An external taper thread runs its
|
||
standard length unless `length` or `up_to` says otherwise (ISO 7-1's useful thread for the basic
|
||
gauge length, NPT's effective thread L2); an internal one the face. A pipe thread has one start and
|
||
turns one way. A taper thread's chamfered tip (`tip`, with its `chamfer_depth`) is measured from the
|
||
major diameter the taper has at that end. ISO 228-1's G sizes are ISO 7-1's gauge-plane diameters
|
||
(1/16 to 6); ISO 228-1's extra sizes (5/8, 7/8, …) are not tabulated yet. ISO 7-1's parallel
|
||
internal thread Rp (`rp`, `Rp 1/2`), the one an R screws into, has the parallel form (H = 0.960491
|
||
P) at the gauge diameters; it is internal only.
|
||
|
||
Trapezoidal clearance ac (ISO 2904): 0.15 mm for P = 1.5, 0.25 mm for P 2 to 5, 0.5 mm for P 6 to
|
||
12, 1 mm for P 14 to 44.
|
||
|
||
The square thread is refused: no current ISO, ASME or DIN standard defines one. Machinery's
|
||
Handbook gives only historical proportions (depth and width P/2; the "modified square" 10°); the
|
||
trapezoidal and Acme forms replaced it.
|
||
|
||
**Sizes.** Without a designation the thread takes the standard size that fits the face: a shaft
|
||
its major diameter, a hole its drill (metric: the tap maker's drill, `docs/thread-catalogue.md`;
|
||
the other forms: the internal minor diameter). Metric uses the ISO 261/262 coarse pitches (M1.6 to M56); trapezoidal and metric
|
||
buttress the ISO 2902 middle pitch of each diameter (Tr8x1.5 to Tr130x14; buttress from S10x2),
|
||
the series DIN 513-2 shares; Acme ASME B1.5's preferred sizes (1/4-16 to 5-2). Buttress inch has
|
||
no size table here: its pitch is always given.
|
||
|
||
**Hand.** `hand: right | left | both`. A left-handed groove is the right-handed one's mirror image
|
||
(the screw motion about the reversed axis, rising along it); `both` cuts a right- and a
|
||
left-handed groove crossing on the face (a reversing screw).
|
||
|
||
**Buttress direction.** `steep_flank: end | start` says which way the steep (load) flank of the
|
||
screw's teeth faces along the thread's axis; a nut cut with the same setting mates with it (its
|
||
own steep flanks face the other way).
|
||
|
||
## Extent
|
||
|
||
`extent: full | length | up_to`, `length`, `up_to` (a point's place along the axis, or where a
|
||
plane crosses it), `from` (a point near the end the thread starts at).
|
||
|
||
A face end is **free** when no material lies past it in the groove's way: over the span from one
|
||
pitch to one and a half past the end, within the radii the groove cuts (the external minor
|
||
diameter to the major, a nut's minor diameter to its root, and the face itself). A cap, a chamfer
|
||
the groove runs out through, a counterbore wider than the thread are free; a shoulder, a head
|
||
whose corners reach past the root, a blind hole's bottom are not.
|
||
|
||
- At a free end the groove runs out a pitch past the end, into the air.
|
||
- At a shoulder that starts at the end of an external thread's face and stays beyond the plane of
|
||
that end, a thread running the whole face goes on through the plane and is trimmed there: the
|
||
root reaches the shoulder at every angle of the last turn, so a nut bottoms out on it, and
|
||
nothing past the plane is cut. A fillet or chamfer at the base stays whole: the groove ends where
|
||
the cylinder does. With no runout, each slice along the axis loses the same, so the groove takes
|
||
exactly length / P turns.
|
||
- At any other closed end (a shoulder rising back along the face, a blind hole's bottom, a
|
||
taper's far end, a length stopping within half a pitch of the end) it stops with its section
|
||
clear of the end: its centre as far inside as the section reaches that way, so it stays out of
|
||
the shoulder at that end.
|
||
- Inside the face it stops square. For a symmetric section a square stop inside material removes
|
||
exactly length / P turns (what the last section leaves uncut ahead of the stop, it cuts behind
|
||
it in mirror image).
|
||
|
||
A thread of some length starts at the end nearest `from`; without it, at the face's only free end;
|
||
without one, at the end the `face` point lies within a third of the face of. A pick in the middle
|
||
of a face whose ends are alike is refused, naming `from`. A length as long as the face runs the
|
||
whole face.
|
||
|
||
## Runout and tip
|
||
|
||
**Runout** (`ease_out`: a length, `standard` = 2.5 P or `short` = 1.25 P, ISO 3508's normal and
|
||
short thread runouts x): the thread's inner end, away from where it starts, fades out over that
|
||
length, shorter than a turn too: its section moves out of the material as it turns (an external
|
||
thread's away from the axis, past the surface; a nut's towards it, into the hole), linearly, by
|
||
SMLib's radial screw sweep, and no end face is left. Without it the groove stops square there,
|
||
ending in its own profile, a flat face in the axial plane. The runout lies past the full-form
|
||
length: beyond a square stop, and before a shoulder up to its clearance (the full form then ends a
|
||
runout short of it); at a free end it lies inside the face, the groove reaching nothing at the
|
||
end. The start never fades: it runs off its free end, cut by the end face, plain or chamfered
|
||
(`tip`); `ease_in` is refused. Where the section moves, the sweep's walls are within its tolerance
|
||
(1e-4 P) of the true surfaces; full-depth turns are exact radially.
|
||
|
||
**Tip** (ISO 4753's chamfered end; `tip: start` the end the thread starts from, which must be
|
||
free, `tip: both` each free end it reaches): at those ends of a modelled external thread, after the groove, the material outside a cone `chamfer_angle` to the axis (45°) reaching
|
||
d_f = d − 2 `chamfer_depth` at the end is cut, the last teeth tapering into it. ISO 4753 bounds
|
||
d_f by the minor diameter; the default is that bound, the external minor diameter d3 = d −
|
||
1.226869 P of ISO 724 (8.160 for M10), which lies below the modelled basic root d1. The cone
|
||
therefore crosses the root and leaves the end a whole disk of d3 inside a whole conical ring; a
|
||
cone ending on the root itself would pinch to nothing wherever the groove reaches the end. ISO
|
||
4753 is for ISO metric threads, so the other forms give `chamfer_depth`. An internal thread takes
|
||
the hole's countersink instead.
|
||
|
||
## Sources
|
||
|
||
- ISO 68-1 (basic profile), ISO 261/262 (sizes), ISO 965-1 (multi-start designation `Ph`).
|
||
- ISO 2901 to 2904 (trapezoidal: basic and design profiles, series, basic dimensions); the
|
||
design diameters checked against the Bornemann Gewindetechnik tables of DIN 103
|
||
(Tr10x2: d3 7.5, D4 10.5, D1 8; Tr40x7: 32, 41, 33; Tr100x20: 78, 102, 80):
|
||
<https://www.bornemann-gewindetechnik.de/de/produkte/trapezgewinde/daten/>.
|
||
- DIN 513-1/-2 (metric buttress): the formulas (ac = 0.11777 P, h3 = 0.86777 P, flat w =
|
||
0.26384 P, D1 = d − 2 H1) and the diameter-pitch table as IS 4696 (Part 3): 2004 publishes them
|
||
in line with DIN 513 (<https://law.resource.org/pub/in/bis/S01/is.4696.3.2004.pdf>), and the
|
||
Bornemann tables (S10x2: d3 6.529, D1 7; S40x7: 27.851, 29.5):
|
||
<https://www.bornemann-gewindetechnik.de/de/produkte/saegengewinde/daten/>.
|
||
- ASME B1.5 (Acme): flat 0.3707 P, h = P/2, the 0.020″/0.010″ minor and major allowances and the
|
||
preferred sizes, as reproduced at <https://torqbolt.com/unified-acme-threads-dimensions-specifications>.
|
||
- ASME B1.9 (buttress inch): 7°/45°, basic height of engagement 0.6 P; the flat follows from the
|
||
fundamental triangle H = P / (tan 7° + tan 45°) = 0.89064 P truncated equally at crest and root.
|
||
- ISO 3508 (thread runouts) and ISO 4753 (ends of parts with external threads) for the runout and
|
||
the chamfered tip. ISO 4753:2011, figure 1 b) (chamfered end CH; the public preview at
|
||
<https://cdn.standards.iteh.ai/samples/55928/38ddde12863b4c2db35dc929fd502a4d/ISO-4753-2011.pdf>):
|
||
the end's diameter "Maximum diameter at the minor thread diameter", the angle ≤ 50°, the
|
||
incomplete thread u ≤ 2 P.
|
||
- ISO 7-1:1978 (taper and parallel 55° profiles: H = 0.960237 P / 0.960491 P, h = 0.640327 P,
|
||
r = 0.137278 P / 0.137329 P, figures 1 and 2; Table 1, columns 1 to 8 and 15: threads per 25.4
|
||
mm, major diameter at the gauge plane, basic gauge length, useful thread), from the public
|
||
preview <https://cdn.standards.iteh.ai/samples/2856/96e1948d3d734f28b2563bcab2920245/ISO-7-1-1978.pdf>;
|
||
the same diameters as G sizes in <https://en.wikipedia.org/wiki/British_Standard_Pipe> and the
|
||
Yamawa YEU23 tables `pipe_thread_catalog.rs` cites.
|
||
- ASME B1.20.1 (NPT) as NBS Handbook H28 (1957) Part II, section VII publishes it: 60°, H =
|
||
0.866025 p, h = 0.800 p, truncation at least 0.033 p, taper 1 in 16, E0 = D − (0.05 D + 1.1) p,
|
||
E1 = E0 + 0.0625 L1, L2 = (0.80 D + 6.8) p, and Table VII.2 (D, n, E0, L1, L2 for 1/16 to 12):
|
||
<https://nvlpubs.nist.gov/nistpubs/Legacy/hb/nbshandbook28supp1957pt2.pdf>.
|
||
- ISO 724 (external minor diameter d3 = d1 − H/6 = d − 1.226869 P, M10x1.5: 8.16), as given at
|
||
<https://www.valvias.com/miscellanea-metric-thread-din-13.php>.
|