This guide covers gaugeable tube fittings in Swagelok catalog MS-01-140. Pipe fittings use catalog MS-01-147 and a different ordering grammar. Metric tube sizes and non-NPT end connections, including ISO/BSP, AN flare, weld, bored-through, and straight-thread forms, are outside this guide.
The Swagelok Fitting Finder assembles documented code segments and decodes each result back before showing it. It states material, tube size, fitting body, and end connection only. It states no pressure rating, temperature rating, material compatibility, or suitability for a service.
1. The ordering grammar, position by position
A supported tube-fitting number starts with the material prefix, followed by the catalog tube-size code and fitting-body code. A supported male connector, male elbow, or bulkhead male connector adds a fourth token for the male-NPT second-end size. Hyphens separate the positions.
The finder does not concatenate unchecked text. It passes the assembled string into the copied decoder and requires a verified-row or in-grammar status plus an exact matched-code echo. A verified-row is a complete number confirmed in a product listing or cited catalog row. In-grammar means the positions are documented, but the exact complete number was not individually confirmed.
2. Inch tube OD and catalog size-code table
The visible size code is the catalog code. It folds the size, series, and component positions together and is not a decimal conversion of the tube OD.
| Tube OD, in | Size code |
|---|---|
| 1/16 | 100 |
| 1/8 | 200 |
| 3/16 | 300 |
| 1/4 | 400 |
| 5/16 | 500 |
| 3/8 | 600 |
| 1/2 | 810 |
| 5/8 | 1010 |
| 3/4 | 1210 |
| 7/8 | 1410 |
| 1 | 1610 |
| 1 1/8 | 1810 |
| 1 1/4 | 2000 |
| 1 1/2 | 2400 |
| 2 | 3200 |
The 1810 code form is grammar-derived and was not independently row-verified. The finder carries that note with every 1 1/8 in result.
3. Worked example: SS-400-6
| Segment | Token | Means |
|---|---|---|
| Material | SS | 316 stainless steel |
| Size (tube OD) | 400 | 1/4 in |
| Fitting type | 6 | union |
Summary: 316 stainless steel union, 1/4 in tube OD, tube x tube ends. Status: confirmed against a Swagelok product listing.
4. Worked example: SS-400-1-4
| Segment | Token | Means |
|---|---|---|
| Material | SS | 316 stainless steel |
| Size (tube OD) | 400 | 1/4 in |
| Fitting type | 1 | male connector |
| Second end size | 4 | 1/4 in male NPT |
Summary: 316 stainless steel male connector, 1/4 in tube OD by 1/4 in male NPT. Status: confirmed against a Swagelok product listing.
5. Fitting bodies this version builds
The twelve supported shapes are union, union elbow, union tee, union cross, bulkhead union, port connector, cap, plug, male connector, 90 degree male elbow, 45 degree male elbow, and bulkhead male connector. Equal-size union tees and crosses use the bare three-token form.
This version does not build female connectors or elbows because its documented numeric end table is male NPT. It also blocks adapters, reducers, reducing elbows, and unequal-size tee or cross forms because their second-end or run/branch tokens need a different interpretation. Positionable run and branch tees use ISO/BSP or straight-thread forms outside this scope.
6. Material prefix table
| Prefix | Material |
|---|---|
| SS | 316 stainless steel |
| B | brass |
| S | carbon steel |
| A | aluminum |
| M | alloy 400 (Monel) |
| HC | alloy C-276 |
| INC | alloy 600 |
| T | PTFE |
| TI | titanium |
| 6ELT | high-temperature 316 stainless steel |
| 6MO | 6-Moly (6% molybdenum austenitic stainless) |
| 625 | alloy 625 |
| 825 | alloy 825 |
| 2507 | alloy 2507 (super duplex) |
The material prefix occupies its own position. It does not change the tube-size or fitting-body code. A documented prefix does not establish material compatibility for a service.
7. The 6 collision and the 810 and 2000 size codes
Code meaning depends on position. In SS-400-6, the trailing 6 is the union fitting-body code. In SS-600-1-6, the third token 1 is the male connector body and the final 6 is a 3/8 in male-NPT end. Treating the same character as the same field is an ordering error.
The tube-size code also carries a series digit. The series digit makes 1/2 in tube code 810, not 800. It returns to zero for 1 1/4 in tube, so that size code is 2000, not 2010. Read the full code from the audited size ladder rather than calculating it from the fraction.
8. Why a selection can return needs-source
The male-NPT end table confirms 1/16, 1/8, 1/4, 3/8, 1/2, 3/4, and 1 in sizes. A 3/16 in tube male connector would suggest a 3/16 in pipe end, but 3/16 NPT is not a standard pipe size and the rows read do not confirm it. The same boundary applies to 5/16 in and 5/8 in end tokens.
A needs-source result withholds the ordering number. It means the copied rows do not support the requested statement. It does not prove that no product exists. Larger tube sizes remain usable with supported tube-only bodies even when there is no same-label NPT default.
9. Before you order
Check the current catalog revision and compare the complete number with the physical part or existing fitting. Confirm tube OD, wall, material, end geometry, installation details, pressure and temperature requirements, and material compatibility for the service. Note whether the result is a confirmed product row or an in-grammar code.
Authorized Swagelok sales and service centers are territory based, so availability is a local question. This guide provides no availability, lead-time, or price information and makes no service-suitability claim.
10. Sources
- Swagelok, Gaugeable Tube Fittings and Adapter Fittings Catalog, document MS-01-140, Additional Ordering Information and Union / Male Connector NPT ordering-number tables, official catalog PDF, captured 2026-06-27. Revision to be confirmed against the current catalog.
- Current official product listings independently corroborate all seven complete verified rows: SS-400-6, SS-400-1-4, B-400-1-4, SS-400-9, SS-600-1-6, SS-810-1-8, and SS-1610-6. Accessed 2026-07-27.
The current catalog and physical part control the final order.