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Backcap Short (with O-Ring) 3 Series, Torch Head Accessories.
Practical answers on choosing, fitting and looking after the individual parts of a larger gas saver torch set-up.
The heat shield sits between the gas lens body and the cup. Its main job is to help seat the cup and seal the joint so shielding gas cannot escape or air be drawn in, and a missing or wrong insulating part can contaminate the shielding gas. Check the torch manual for exactly what it does on your torch.Torch makers list separate heat shields for standard, short and large diameter gas lens set-ups, so they are not normally interchangeable. Inspect it whenever you change the cup, and replace it if it is cracked, crumbling, distorted or no longer seats the cup firmly, because a poor seal can let air into the gas.
Back cap length is mainly about how much tungsten you need to fit and how much room you have behind the torch head. A long cap takes a full-length electrode, a medium cap is a general-purpose compromise, and a short cap helps in tight spaces but usually means the tungsten has to be cut shorter so that it fits.Caps are made for a specific torch series, so match the series first and then pick the length. Whichever you choose, check that the cap has its O-ring and that it tightens fully without forcing.
These are two separate choices. A standard collet is slotted and is squeezed onto the tungsten as the back cap is tightened. A wedge collet is a single piece with an angled end that presses against the collet body, and it is usually described as more durable than a slotted type.Stubby (short) describes length. A shorter collet normally goes with a shorter gas lens body and helps access in tight joints, while a standard-length collet goes with a standard body. Lengths differ between makers, so confirm the collet suits your lens body and tungsten diameter before choosing, and check the torch manual if the fit is unclear.
A larger lens body and cup spread a wider blanket of shielding gas, and a gas lens generally lets the tungsten stick out further while keeping good cover. Makers' technical guidance says larger nozzle diameters give a longer laminar flow, while smaller ones suit tight spaces but raise gas velocity and turbulence.The trade-offs are a bulkier torch head that can block access or your view of the joint, and the need for correctly matched larger parts. Longer stick-out also leaves more tungsten exposed, so pre-flow and post-flow matter. Gas settings depend on the cup, joint and conditions, so follow the torch maker's guidance and test on scrap before welding a real joint.