CSMC403 - Smith Style MC40-3 Propane Cutting Tip Size 3

Technical Overview of the Smith Style MC40-3

The CSMC403 is a high-performance aftermarket cutting tip engineered to replicate the specifications of the Smith MC40-3. Designed specifically for alternative fuel gases—namely Propane (LP) and Natural Gas—this tip features a specialized two-piece construction. Unlike single-piece acetylene tips, the two-piece design consists of a brass inner member with splined preheat passages and a copper outer shell. This configuration creates a recessed tip end, which is critical for burning alternative fuels. Propane has a lower flame propagation velocity than acetylene; the recess acts as a combustion chamber to anchor the flame, preventing it from blowing off the tip even at high pressures or in drafty conditions.

The "Size 3" classification indicates the oxygen orifice diameter is calibrated for cutting mild steel ranging from 1-1/2 inches (38mm) to 2 inches (51mm) in thickness. The preheat splines are designed to deliver a medium-to-heavy preheat flame, compensating for the lower flame temperature of propane compared to acetylene by increasing the BTU output volume. This ensures rapid bring-to-temperature times, even on plate that may have minor scale or rust.

This tip is manufactured with standard Smith-style threading to ensure full compatibility with Medium Duty cutting assemblies, specifically the MC505 and MC509 attachments found on AW1A and AW10A torch handles. The seating surfaces are precision-machined to ensure a gas-tight metal-to-metal seal, preventing dangerous leaks inside the torch head. Operators utilizing this tip must ensure their gas supply system (regulators and hoses) is rated for propane (Grade T hose is required) to maintain safety and performance standards.