1/4 BSP to 5/8-18 RH Adapter for TIG Torches
By MIG/TIG/Stick Welders & Plasma Cutters | USA Weld – HTP ... | Published: 2026-10-24
Category: Buying Guides
Learn how the 1/4 BSP to 5/8-18 RH adapter solves gas fitting mismatches on HTP welding machines, with clear decision rules and fit guidance.
Quick answer
If your HTP welding machine uses a 1/4 BSP female gas connection and you need to attach a torch or hose with a 5/8-18 RH female fitting, this adapter is the direct solution.
Why the thread mismatch happens
HTP welding machines ship with a 1/4 BSP female gas inlet. Many TIG torches and gas hoses in North America use the 5/8-18 RH thread standard. Without an adapter, the two cannot connect.
What this adapter does
The adapter converts the machine-side 1/4 BSP female port to a 5/8-18 RH female port. This lets you use standard 5/8-18 RH male fittings on your torch or hose. It is a simple mechanical adapter with no seals or valves.
Installation notes
Hand-tighten the adapter onto the machine's 1/4 BSP male fitting. Then attach your 5/8-18 RH male gas fitting. Use a backup wrench on the adapter body to avoid over-torquing. No thread sealant is required if the fittings are clean and dry, but a small amount of PTFE tape on the BSP threads can help.
Decision rules for buying this adapter
- Check your machine's gas port: Confirm the port is 1/4 BSP female. Most HTP machines use this standard. If your port is different, this adapter will not fit.
- Check your torch or hose fitting: Verify the male fitting is 5/8-18 RH. If it is a different standard (e.g., 35 Dinse, 9/16-18), you need a different adapter.
- Consider gas type and pressure: This adapter works for argon, CO2, or mixed shielding gases at typical TIG pressures (up to 50 psi). For high-pressure applications, verify with the manufacturer.
- Thread direction: Both 1/4 BSP and 5/8-18 RH are right-hand threads. No left-hand thread adapters are involved.
Product details
- 1/4 BSP Female to 5/8-18 RH Female Adapter: This 1/4" BSP Female to 5/8 -18RH Female adapter lets you adapt your HTP welding machine gas connection from the standard 1/4 BSP female fitting to the more commonly found 5/8 -18RH gas fitting. It eliminates the need to replace the machine's gas inlet or modify your torch setup, saving time and cost.
1/4 BSP Female to 5/8-18 RH Female Adapter
Who should buy this adapter
Best for
- HTP welding machine owners who need to connect a TIG torch with a 5/8-18 RH male fitting
- Welders who want to use a standard North American gas hose on an HTP machine
Not for
- Machines with non-1/4 BSP gas ports (e.g., 1/8 BSP, NPT)
- Torches or hoses with 35 Dinse, 9/16-18, or other non-5/8-18 RH fittings
