A buyer sends over a list of Swagelok part numbers and asks, "Can you match these in DK-Lok?" Most of the time the answer is yes, and once you know how both numbering systems are built, you can read most of the list yourself. After 20 years in the instrumentation valve and fitting business, here's how I walk people through it.
How a Swagelok Tube Fitting Part Number Reads
Take SS-400-1-4. Read it left to right:
- SS is the material. SS is 316 stainless, B is brass.
- 400 is the tube OD in sixteenths of an inch. 400 is 4/16, or 1/4". 600 is 3/8". Watch the 1/2" size: it's 810, not 800.
- 1 is the configuration. -1- is a male connector, -7- is a female connector and -6 is a union.
- 4 is the pipe thread size, also in sixteenths. -4 is 1/4" NPT, -2 is 1/8" NPT, -8 is 1/2" NPT.
So SS-400-1-4 is a 316 stainless male connector, 1/4" tube to 1/4" male NPT. Metric sizes use an M, like 6M0 for 6 mm tube.
How a DK-Lok Part Number Reads
DK-Lok puts the configuration first and the material last. The same part is DMC4-4N-S:
- DMC is the fitting type, a male connector. DCF is a female connector and DU is a union.
- 4 is the tube OD in sixteenths, so 1/4". On DK-Lok, 1/2" tube is simply 8. Metric tube adds an M, like 6M for 6 mm.
- 4N is the thread: 1/4" NPT.
- S is the material, 316 stainless. C is carbon steel.
On our website you may see the same part written with an extra dash, like DMC-4-4N-S. It's the same fitting.
Three Quick Examples
- SS-400-1-4 (male connector, 1/4" tube x 1/4" NPT) → DMC4-4N-S
- SS-400-7-4 (female connector, 1/4" tube x 1/4" NPT) → DCF4-4N-S
- SS-810-6 (union, 1/2" tube) → DU8-S
What to Double-Check Before You Order
Part numbers get you close, but these are the spots where I see mistakes:
- Metric vs. fractional. A 6 mm fitting and a 1/4" fitting look alike. They don't seal on each other's tube.
- Thread type. NPT, BSPT and straight threads are not interchangeable. Confirm what's in the port.
- Material. Match like for like: 316 with 316, brass with brass.
- Special suffixes. Extra letters on the end can mean a special cleaning, alloy or option. Send us the whole number, not a shortened one.
Can You Mix Them in the Same System?
Yes. DK-Lok tube fittings are 100% interchangeable and intermixable with Swagelok and Parker A-Lok for like size and material, properly assembled per the DK-Lok catalog. In ASTM F1387 testing witnessed by TÜV Rheinland, 14 combinations of intermixed DK-Lok and Swagelok nuts, front ferrules, back ferrules and bodies passed every test, with "No failure observed," and DK-Lok backs it with a written intermix guarantee. See also the Parker A-Lok interchangeability letter.
When the replacement goes in, make it up per the DK-Lok catalog. Once the line is pressurized per your site procedure, apply Gator Leak Detector all the way around each joint you touched and watch for bubbles or foam. On male connectors and other NPT-to-tube fittings, check the pipe-thread joint as well as the tube nut, since the NPT side is often skipped. If something leaks, isolate and depressurize before putting a wrench on it. Never tighten a fitting under pressure.
Send Us the List
You don't have to decode a whole BOM yourself. Send it to A-Best Industrial Inc. Fittings, Valves, and Tubing through our DK-Lok part number crossover page and we'll quote the brand you asked for plus the matching DK-Lok part. We're an authorized DK-Lok distributor, and we also supply Swagelok and Parker when a project needs them. Browse our compression tube fittings to see what's in stock.
Call 310-833-3353 or email sales@abesttube.com. We're open Monday–Friday, 8:00 AM–5:00 PM Pacific, with after-hours emergency service.
Swagelok and Parker A-Lok are trademarks of their respective owners. Brand names are used only to identify the parts customers ask us to quote.