# Tri-clamp instrument head: ISO 2852 cap with Ø6, Ø3 and Ø4 probe ports, 1.5, 2 and 3 in

> How do I put a temperature probe through a tri-clamp end cap?

- Category: Stirling engines › Tri-clamp engine parts
- Kind: Hardware
- Basis: ISO 2852 cap face with three ported bosses on the C2 − 16 circle, each with an M3 pinch hole (Ø2.5)
- Page: https://xemstudio.com/objects/tri-clamp-instrument-head/ · JSON: https://xemstudio.com/api/geometry?object=tri-clamp-instrument-head · Plain text: https://xemstudio.com/objects/tri-clamp-instrument-head/sheet.txt
- License: dimension sheet CC BY 4.0 (Xem Studio); linked files under their publishers' licenses

**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

- An ISO 2852 end cap with three probe ports, so a cylinder can be instrumented without drilling a flat cap.
- Ports: Ø6 (a DS18B20 sleeve), Ø3 (a K-type sheath) and Ø4 (a 4 mm tube), 120° apart on a circle of radius C2/2 − 8 (13.75 / 20.25 / 33.75 mm for 1.5 / 2 / 3 in).
- Each port has a boss 6 mm larger than its bore, 10 mm tall on the back of the 6 mm cap, and an Ø2.5 radial hole at 11 mm for an M3 pinch screw that holds the probe.

## 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 |
|---|---|---|---|---|
| head faces | ISO 2852 | ferrule face + Type B gasket | clamp | head-* |
| probe / port bores | Ø6 / Ø3 / Ø4 | DS18B20 sleeve / K-type sheath / 4 mm tube (M3 pinch) | slide | head-instrument-* |
| pinch screw holes | Ø2.5 | M3 tap drill | designed | head-instrument-* |

## Sizes

| size_in | flange_od_mm | port_circle_r_mm | ports_mm | pinch |
|---|---|---|---|---|
| 1.5 | 50.5 | 13.75 | Ø6 / Ø3 / Ø4 | M3 (Ø2.5) |
| 2 | 64.0 | 20.25 | Ø6 / Ø3 / Ø4 | M3 (Ø2.5) |
| 3 | 91.0 | 33.75 | Ø6 / Ø3 / Ø4 | M3 (Ø2.5) |

## Where the files are

- Long Earth Society: [Tri-clamp Stirling engine builds](https://longearthsociety.com/engineering/) — web, video — LES site
- James R. Senft: [An Introduction to Low Temperature Differential Stirling Engines (displacer and gap design)](https://www.stirlingengine.com/) — book — Moriya Press (verify at link)
- Wikipedia: [Stirling engine](https://en.wikipedia.org/wiki/Stirling_engine) — web — CC BY-SA 4.0 (text)

## Free STEP/STL (3 parts, CC BY 4.0, Xem Studio)

Index: https://xemstudio.com/files/hardware/tri-clamp-instrument-head/index.json

- head-instrument-1.5in: [STEP](https://xemstudio.com/files/hardware/tri-clamp-displacers-and-heads/head-instrument-1.5in.step) · [STL](https://xemstudio.com/files/hardware/tri-clamp-displacers-and-heads/head-instrument-1.5in.stl) — 1.5 in ISO 2852 cap: Ø6 bore for a DS18B20 sleeve, Ø3 for a K-type sheath, Ø4 port for a 4 mm tube, each with an M3 pinch screw (Ø2.5 tap drill)
- head-instrument-2in: [STEP](https://xemstudio.com/files/hardware/tri-clamp-displacers-and-heads/head-instrument-2in.step) · [STL](https://xemstudio.com/files/hardware/tri-clamp-displacers-and-heads/head-instrument-2in.stl) — 2 in ISO 2852 cap: Ø6 bore for a DS18B20 sleeve, Ø3 for a K-type sheath, Ø4 port for a 4 mm tube, each with an M3 pinch screw (Ø2.5 tap drill)
- head-instrument-3in: [STEP](https://xemstudio.com/files/hardware/tri-clamp-displacers-and-heads/head-instrument-3in.step) · [STL](https://xemstudio.com/files/hardware/tri-clamp-displacers-and-heads/head-instrument-3in.stl) — 3 in ISO 2852 cap: Ø6 bore for a DS18B20 sleeve, Ø3 for a K-type sheath, Ø4 port for a 4 mm tube, each with an M3 pinch screw (Ø2.5 tap drill)

## How it fits

### Goes in or on
- [Tri-clamp spool (two ferrules on a tube), 1.5 and 2 inch](https://xemstudio.com/objects/tri-clamp-spool/): ISO 2852 face on any ferrule of its size

### Connects to
- [Split probe clamps for Ø3, Ø4.8, Ø6 probes and Ø8 / Ø9.53 dial-indicator stems](https://xemstudio.com/objects/probe-clamps/): DS18B20 sleeve Ø6, K-type sheath Ø3
- [Silicone tube 1 × 3 to 10 × 14 mm (ID × OD)](https://xemstudio.com/objects/silicone-tube/): 4 mm tube in the Ø4 port

### Also needed
- [Tri-clamp clamp, two-bolt: every flange size ½ to 4 in](https://xemstudio.com/objects/tri-clamp-clamps/): clamp and gasket on the face

## Questions

**What probes fit the instrument head?**

A Ø6 DS18B20 sleeve, a Ø3 K-type sheath and a 4 mm tube, each in its own bore with an M3 pinch screw.

**Where are the ports?**

120° apart on a 20.25 mm radius on the 2 in head (13.75 on 1.5 in, 33.75 on 3 in).

## Fits with

- [Split probe clamps for Ø3, Ø4.8, Ø6 probes and Ø8 / Ø9.53 dial-indicator stems](https://xemstudio.com/objects/probe-clamps/)
- [Tri-clamp displacer head: ISO 2852 cap with Ø3 rod bore and 4 mm barb, 1.5, 2 and 3 in](https://xemstudio.com/objects/tri-clamp-displacer-head/)
- [Tri-clamp end cap, 6 mm flat: 1.5 and 2 in](https://xemstudio.com/objects/tri-clamp-end-cap/)
- [Tri-clamp clamp, two-bolt: every flange size ½ to 4 in](https://xemstudio.com/objects/tri-clamp-clamps/)
- [Silicone tube 1 × 3 to 10 × 14 mm (ID × OD)](https://xemstudio.com/objects/silicone-tube/)