CNC Turned Stainless Steel Sensor Fitting
CNC turned 316L stainless sensor fittings for temperature probes, pressure sensors and level switches, with M8 to M18 or G1/8 to G1/2 threads, a probe bore concentric to the thread within 0.02 mm and a seal face flat to 0.01 mm. Each fitting is leak tested at 25 bar before packing.
- Thread and Bore Concentric to 0.02 mm
- Seal Face Flat to 0.01 mm
- 316L for Washdown
- Leak Tested 100%
*Tell us the probe diameter and how deep it must sit. The bore depth and the seal face position together decide the immersion depth, and a fitting that is 2 mm short will read the wall instead of the fluid.
Stainless Sensor Fitting Overview
A sensor fitting has to do three things at once: hold the probe on axis, seal against the process fluid and survive washdown. The critical dimension is not the thread but the relationship between the thread axis and the sealing face, because that is what decides whether the O-ring compresses evenly.
The fitting is turned from 316L bar in one cycle, with the thread cut on the same axis as the bore, then the hex is milled and the seal face is finished in a second operation against the thread. Threads are gauged and the assembly is pressure tested rather than sample checked.
316L Stainless Steel
316L is used for food, beverage and washdown service because it resists chloride attack and does not pit at the thread root. It work-hardens during turning, so depth of cut is kept above the work-hardened layer to avoid a smeared thread flank.
304 / 316Ti for High Temperature
316Ti is specified when the fitting sits on an exhaust or a process line above 400 °C, where the titanium stabilisation stops carbide precipitation at the thread. 304 is the lower-cost choice for dry indoor panel mounting.
Stainless grade follows the fluid and the temperature, not the pressure. A washdown fitting needs 316L even at 6 bar, and a high-temperature port needs stabilised grade even when dry.
Stainless Sensor Fitting Specifications
Turning and test data for threaded sensor fittings, with the concentricity and seal face tolerances that decide whether the probe seals.
| Specification | Machining Data | Specification | Machining Data |
|---|---|---|---|
| Product | Threaded Sensor Fitting / Probe Housing | Machining Process | CNC Turning, Threading, Hex Milling |
| Material | 316L Stainless Steel Bar | Thread Tolerance | 6g, Gauged Go / No-Go |
| Thread Range | M8 × 1 to M18 × 1.5, G1/8 to G1/2, NPT | Bore to Thread Concentricity | 0.02 mm |
| Probe Bore | 3 – 12 mm, Blind or Through | Seal Face Flatness | 0.01 mm, Ra 0.8 µm |
| Hex Size | 12 – 27 mm A/F | Hex to Thread Squareness | 0.05 mm |
| Length Range | 20 – 80 mm | Surface Finish | Ra 0.8 µm Bore, Ra 1.6 µm Body |
| Sealing | O-Ring Groove, Bonded Washer Face, Taper Thread | Pressure Rating | 16 bar (Tested at 25 bar) |
| Customization | Probe Depth, Hex, Thread, Cable Exit, Marking | Lead Time | 5 – 7 Days (Sample), 10 – 14 Days (Batch) |
| Inspection | Thread Gauges, Bore Pin Gauge, Concentricity, Leak Test | Packing | Thread Caps, Individually Bagged, Carton |
Key Features of Our Turned Sensor Fittings
Turned and threaded on one axis so the probe, the seal and the port all agree.
Thread and Bore on One Axis
The probe bore is finished before the thread is cut, so the two stay concentric within 0.02 mm and the probe does not rub one side of the bore as it is inserted.
Seal Face Finished Against the Thread
The sealing face is faced in a second operation held on the thread, which keeps it square to the port rather than to the bar end.
Gauged Threads, Not Sampled
Every thread is checked with go/no-go gauges, and a failing thread is re-cut or scrapped instead of being sent with a sealant instruction.
Pressure Tested Per Piece
Each fitting is held at 25 bar with a blanking plug and checked for weep at the thread and seal face before it is packed.
Need a sensor fitting that seals first time?
Surface Finishes for Stainless Sensor Fittings
The bore and the thread see different conditions, so the finish is chosen for the fluid side and the assembly side separately.
| Finish | Main Purpose | Finish | Main Purpose |
|---|---|---|---|
| Passivation | Restores the oxide layer after machining 316L | Electropolishing | Bright bore for hygienic probe assemblies |
| Glass Bead Blasting | Even matte body on visible panel fittings | PTFE Coating | Anti-galling on stainless threads used in aluminium |
| Laser Marking | Thread size and batch code on the hex | Ultrasonic Cleaning | Clears cutting oil from the probe bore |
*PTFE coating on the thread adds 10 to 15 µm and changes the pitch diameter. Coated fittings are threaded to a pre-plate size and gauged after coating.
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Turning Process for Stainless Sensor Fittings
The thread, the hex and the probe bore are cut on one axis, so the sensor seats square and reads the same depth in every port.
01. Probe and Port Review
Check the probe diameter, immersion depth and port thread against the drawing, and confirm the seal type, since an O-ring groove and a bonded washer need different face geometry.
02. Bar Cut and First Op
Cut 316L bar to length, face it, turn the body profile, drill and bore the probe bore to size and cut the thread in the same cycle so both share an axis.
03. Hex and Second Op
Mill the hex, then hold the part on the thread to face the seal face square and cut the O-ring groove to depth.
04. Cleaning and Passivation
Ultrasonic clean the bore to remove cutting oil, then passivate so the machined surfaces recover their corrosion resistance before test.
05. Gauge, Test and Pack
Gauge the thread, pin-gauge the bore, leak test at 25 bar, then cap the thread and bag each fitting with a batch label.
Send the probe drawing, the port thread and the fluid, and we will quote the fitting with the seal face and bore depth already set.
Stainless Sensor Fitting FAQs
Yes. A blind pocket is bored to depth with a flat or drill-point bottom and the depth is held to ±0.1 mm, which matters when the probe tip has to sit a fixed distance from the process wall.
A PTFE-coated thread or an O-ring face seal. Stainless threads gall in aluminium, and a coated thread avoids the seizure that makes the fitting unserviceable after the first removal.
Up to eight times the bore diameter with a drilled hole, and ten times with a bored and reamed hole. Beyond that the drill wanders and the concentricity callout can no longer be held.
Every fitting is pressure tested at 25 bar for one minute. Sampling is only used for repeat orders where the process and material are unchanged and the first article has been approved.
Yes. Hex sizes from 12 to 27 mm A/F are milled to standard wrench sizes, and the hex is held square to the thread within 0.05 mm so the fitting does not sit cocked when tightened.
Five to seven days for a sample including programming, turning, passivation and leak test. Batches of 100 to 500 pieces run ten to fourteen days depending on the thread size and whether coating is required.
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