# SMT spacer (Würth Elektronik WA-SMSI / WA-SMST / WA-SMSE / WA-SMSR)

Surface-mount steel spacers of Würth Elektronik for mounting boards, at any length. Presets cover the catalogue's
Würth order codes (KiCad's `Mounting_Wuerth` footprints): each preset is one order code.

## Geometry

Round steel spacers, axis along +Z, centred on the origin; **z = 0 is the shoulder** that sits on the board.

- **WA-SMSI** (internal thread) and **WA-SMST** (plain bore): a body Ø D from z = 0 to **L**, over a locating collar
  Ø Dc × c below z = 0, with the bore through (a thread is drawn at its nominal diameter; the thread is not
  modelled). Overall height L + c.
- **WA-SMSI M1.6 variants** (order codes 9773…): `blind` (…4: collar, thread from the top to depth **Tli** only),
  `closed` (…0, "No NPTH": no collar, blind thread), `pin` (…2: a Ø0.8 × 0.5 pin instead of the collar, blind
  thread). The drill point below a blind thread is not dimensioned and not modelled.
- **WA-SMSE** (external thread): a body Ø D from z = 0 to L, an M3 stud 6 long on top (nominal diameter; thread and
  undercut not modelled) and a Ø0.8 × 0.5 pin underneath.
- **WA-SMSR** (reverse mount): a flange Ø D × 1.0 (z = 0 to 1) over a shank Ø Dc, **G** long below z = 0 (the
  `length` parameter is G), bore through.

Chamfers and the pick-and-place tape are not modelled.

## Parameters

| Parameter | Meaning |
|---|---|
| `spacer` | series and size (table below) |
| `length` | L, the body length above the shoulder (WA-SMSR: the shank length G), mm |
| `thread_depth` | Tli, the blind thread depth of the M1.6 `blind`, `closed` and `pin` variants, mm |

## Sources

Würth Elektronik eiSos, one datasheet per order code, page 1, *WA-SMSI / WA-SMST / WA-SMSE / WA-SMSR SMT Steel
Spacer*, general tolerance DIN ISO 2768-1m, L ± 0.1 mm: `https://www.we-online.com/components/products/datasheet/<order code>R.pdf`.
Read for this recipe (revision, date): 9774020633 (001.003, 2025-12-30), 97730406334, 97730406330, 97730406332 (001.003,
2025-12-30), 9774040243 (001.003, 2025-12-31), 9774040151 (001.002), 9774005151 (001.001), 9774030360 (001.003),
9774040482 (001.003), 9774040943 (001.004), 9774040951 (001.002), 9774040960 (002.002), 9774040982 (001.003), all
2025-12-31; 9771100360 (001.004, 2026-01-22); 9775046360 and 9775046960 (001.005, 2025-12-31). The drawings are the
same across a series; only L (or G) changes.

The order code → length tables come from Würth's product pages, `https://www.we-online.com/en/components/products/`
+ `SMSI_SMT_STEEL_SPACER_M1_6_INTERNAL_THREAD`, `…_M1_6_INTERNAL_BOTTOM_CLOSED`, `…_M1_6_INTERNAL_BOTTOM_CLOSED_W_PIN`,
`SMSI_SMT_STEEL_SPACER_M2_THREAD_INTERNAL`, `…_M2_5_…`, `…_M3_…`, `…_M4_…`, `SMST_SMD_STEEL_SPACER_{2_25,2_7,3_3,4_5}_INTERNAL_NON_STOP`,
`SMSE_SMD_STEEL_SPACER_M3_THREAD_EXTERNAL`, `SMSR_SMD_STEEL_SPACER_M3_THREAD_INTERNAL`,
`SMSR_SMD_STEEL_SPACER_3_2_INTERNAL_NON_STOP`. In an order code 9774LLLxxx (9771…, 9775…) LLL is the length × 10.

| `spacer` | Würth series | Body Ø D | Collar Ø Dc × c | Bore |
|---|---|---|---|---|
| SMSI-M1.6 | WA-SMSI M1.6 (9774…633) | 3.3 | 1.9 × 0.7 | M1.6 through |
| SMSI-M1.6-blind | WA-SMSI M1.6, thread depth (9773…6334) | 3.3 | 1.9 × 0.7 | M1.6, Tli 2 |
| SMSI-M1.6-closed | WA-SMSI M1.6 bottom closed (9773…6330) | 3.3 | – | M1.6, Tli 1.5 (L 2.5), 1.8 (L 3), 2 (L 3.5–6) |
| SMSI-M1.6-pin | WA-SMSI M1.6 with pin (9773…6332) | 3.3 | pin 0.8 × 0.5 | as …6330 |
| SMSI-M2 | WA-SMSI M2 (9774…243) | 4.35 | 2.8 × 1.4 | M2 through |
| SMSI-M2.5 | WA-SMSI M2.5 (9774…151) | 5.1 | 3.5 × 1.4 | M2.5 through |
| SMSI-M3 | WA-SMSI M3 (9774…360) | 6.0 | 4.2 × 1.4 | M3 through |
| SMSI-M4 | WA-SMSI M4 (9774…482) | 8.2 | 5.2 × 1.4 | M4 through |
| SMST-2.25 | WA-SMST Ø2.25 (9774…943) | 4.35 | 2.8 × 1.4 | Ø2.25 ± 0.05 |
| SMST-2.7 | WA-SMST Ø2.7 (9774…951) | 5.1 | 3.5 × 1.4 | Ø2.7 +0.03/−0.02 |
| SMST-3.3 | WA-SMST Ø3.3 (9774…960) | 6.0 | 4.2 × 1.4 | Ø3.3 +0.1/0 |
| SMST-4.5 | WA-SMST Ø4.5 (9774…982) | 8.2 | 5.2 × 1.4 | Ø4.5 |
| SMSE-M3 | WA-SMSE M3 (9771…360) | 6.0 | pin 0.8 × 0.5 | M3 stud × 6.0 on top |
| SMSR-M3 | WA-SMSR M3 (9775…360) | flange 6.0 × 1.0 | shank 4.2 × G | M3 through |
| SMSR-3.2 | WA-SMSR Ø3.2 (9775…960) | flange 6.0 × 1.0 | shank 4.2 × G | Ø3.2 ± 0.05 through |

Not covered: WA-SMSSR snap rivets (the snap lip's thickness is not dimensioned), WP-SMRA (two features of the drawing
are not described), and Phoenix Contact 1201578 (its sources disagree on the outline and the clip is not
dimensioned).

Preset list: the step.parts catalogue's Würth entries (MIT), see `library/NOTICE.md`.