# 2 in × 6 in spool with three 1/4 NPT bosses at mid-length

> How do I put gauge, fill and relief ports on a tri-clamp spool?

- Category: Hardware › Stirling & thermoacoustic
- Kind: Hardware
- Basis: Stock 2 in × 6 in spool; 1/4 NPT per ASME B1.20.1; boss size and positions are design values
- Page: https://xemstudio.com/objects/tri-clamp-spool-npt-bosses/ · JSON: https://xemstudio.com/api/geometry?object=tri-clamp-spool-npt-bosses · Plain text: https://xemstudio.com/objects/tri-clamp-spool-npt-bosses/sheet.txt
- License: dimension sheet CC BY 4.0 (Xem Studio); linked files under their publishers' licenses
- Use in every chat: add https://xemstudio.com/mcp as a connector (https://xemstudio.com/use-with-ai/)

**Exact dimensions.** Every file is drawn at true size with no printing tolerance. The holes and pins that meet another part are listed below under Mating features, with the fit each joint needs; open those by your printer's or process's clearance before making the part.

## Notes

- A standard 2 in × 6 in spool with three welded 1/4 NPT bosses round its middle: fill valve, pressure gauge and relief valve on one charged space.
- On the horizontal gamma it is the bounce space behind the power piston: about 0.37 L that holds the mean charge so the piston only works against the cycle's swing.

## Mating features (exact size; open press / slide / run / socket by your process clearance, leave designed and clamp as drawn)

| feature | exact | mates with | fit | files |
|---|---|---|---|---|
| faces | ISO 2852 2 in, 152.4 face to face | Type B gaskets, 2 in clamps | clamp | all |
| NPT bosses | 3 × 1/4-18 NPT, tap drill Ø11.1 × 12, Ø6 through | fill valve, gauge, relief valve (1/4 NPT male) | designed | all |

## Sizes

| feature | value |
|---|---|
| length | 152.4 face to face |
| bosses | 3 × 1/4 NPT at mid-length, 90° / 30° / 150° |
| boss | Ø22 to r 36, tap drill Ø11.1 × 12, Ø6 on |

## Where the files are

- ISO (via iTeh sample): [ISO 2852 clamp liners: face profile and flange / groove diameters](https://cdn.standards.iteh.ai/samples/7850/eb49c396488d408c8ced3e2961d76cf3/ISO-2852-1974.pdf) — PDF — standard excerpt; dimensions are facts
- ASME: [BPE Bioprocessing Equipment (clamp fitting dimensions, tube OD and wall)](https://www.asme.org/codes-standards/find-codes-standards/bpe-bioprocessing-equipment) — standard — ASME; dimensions are facts (verify at link)
- ASME: [ASME B1.20.1 Pipe Threads, General Purpose, Inch (NPT): 1/4-18 major Ø13.72, tap drill 7/16 in (11.1), L2 10.2](https://www.asme.org/codes-standards/find-codes-standards/b1-20-1-pipe-threads-general-purpose-inch) — standard — ASME; dimensions are facts (verify at link)
- Long Earth Society: [Engine builds](https://longearthsociety.com/engineering/) — web, video — LES site

## Free STEP/STL (1 parts, CC BY 4.0, Xem Studio)

Index: https://xemstudio.com/files/hardware/tri-clamp-spool-npt-bosses/index.json

- spool-2in-6in-3x-npt14: [STEP](https://xemstudio.com/files/hardware/tri-clamp-spool-npt-bosses/spool-2in-6in-3x-npt14.step) · [STL](https://xemstudio.com/files/hardware/tri-clamp-spool-npt-bosses/spool-2in-6in-3x-npt14.stl) — 2 in × 6 in (152.4) spool, ISO 2852 faces, stock bore, three 1/4 NPT bosses at mid-length (90°, 30°, 150° from +X; Ø22 out to r 36, tap drill Ø11.1 × 12, Ø6 through the wall)

## Questions

**Which port is which?**

Top: fill valve. The two at 30° and 150°: gauge and relief.

## Fits with

- [2 in end cap with a bored boss for two 8 × 12 × 20 sleeve bushings (piston-rod gland)](https://xemstudio.com/objects/tri-clamp-rod-gland-cap/)
- [Build list: Tri-clamp horizontal gamma generator, 2 in, chargeable](https://xemstudio.com/objects/list-tri-clamp-horizontal-gamma/)