# Heat-set insert (SPIROL Series 19, metric)

Threaded inserts for plastics, installed with heat or ultrasound: SPIROL Series 19 metric, **short** and **long**, M2
to M4. Presets cover the catalogue's generic short and long heat-set inserts, each mapped to SPIROL's short or long
insert of that thread (SPIROL is the maker found with exactly one short and one long insert for each of M2, M2.5, M3
and M4).

## Geometry

Envelope: a cylinder of the overknurl diameter **A** (a reference size) and length **L**, axis along +Z, one end on the
XY plane, centred on the origin; the thread is drawn as a plain bore at its nominal diameter. The knurl bands and the
pilot are not dimensioned in SPIROL's tables and are not modelled.

## Parameters

| Parameter | Meaning |
|---|---|
| `size` | Thread: M2, M2.5, M3, M4 |
| `variant` | `short` or `long` |
| `material` | `brass` (CuZn36Pb3) or `aluminium` (SPIROL offers both) |

## Sources

- SPIROL, *Series 19 Short Heat / Ultrasonic Insert — Metric*, online catalogue table:
  https://shop.spirol.com/viewitems/series-19-20-short-heat-ultrasonic-insert-metric/series-19-short-heat-ultrasonic-insert-metric?pcat=euro
- SPIROL, *Series 19 Long Heat / Ultrasonic Insert — Metric*:
  https://shop.spirol.com/viewitems/series-19-20-long-heat-ultrasonic-insert-metric/series-19-long-heat-ultrasonic-insert-metric?pcat=euro
- Recommended hole diameters (+0.08 / −0): SPIROL item print pages of the items below
  (https://shop.spirol.com/.../printitem/...) and SPIROL's white paper *How to Design the Proper Hole for Heat /
  Ultrasonic Inserts* (© 2022, https://uk.spirol.com/assets/files/ins-wp-how-to-design-the-proper-hole-for-heat-ultrasonic-inserts-uk.pdf):
  minimum hole depth L + 2 thread pitches, hole taper at most 1° included.

| Thread | Variant | SPIROL item (brass) | Overknurl Ø A | Length L | Hole Ø |
|---|---|---|---|---|---|
| M2 × 0.4 | short | 151053 | 3.58 | 3.18 | 3.20 |
| M2 × 0.4 | long | 150949 | 3.63 | 3.99 | 3.20 |
| M2.5 × 0.45 | short | 151054 | 4.62 | 3.56 | 3.99 |
| M2.5 × 0.45 | long | 150989 | 4.75 | 5.74 | 3.99 |
| M3 × 0.5 | short | 150829 | 4.62 | 3.56 | 3.99 |
| M3 × 0.5 | long | 150419 | 4.75 | 5.74 | 3.99 |
| M4 × 0.7 | short | 150832 | 6.25 | 4.70 | 5.61 |
| M4 × 0.7 | long | 150421 | 6.38 | 8.15 | 5.61 |

Aluminium items of the same sizes: 325155, 325126 (M2), 325156, 325129 (M2.5), 325157, 325130 (M3), 243879, 311471
(M4).

Other makers checked: CNC Kitchen (M2 × 3, M2.5 × 4, M3 × 3 short, M3 × 5.7, M4 × 4 short, M4 × 8.1; official table
https://cnckitchen.store/cdn/shop/files/table_metric.png) and ruthex have no short M2 or M2.5, so they do not cover the
catalogue's eight entries.

Preset list: sizes of the step.parts catalogue (MIT), see `library/NOTICE.md`.