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Thermal Dynamics Torches

Thermal Dynamics Torches FAQs

Practical answers on choosing, using and looking after a replacement plasma torch and lead.

What is the difference between rated cut and severance cut when choosing a torch?icon-minus-redicon-plus-red

Cutting capacity is usually quoted in two ways. The rated, or clean, cut is the thickness the equipment can cut at a reasonable speed with a good edge. The severance cut is the absolute maximum it can part, at a slow speed and with a rougher edge.

Size your equipment so the clean-cut rating covers the metal you cut most often, and treat severance as an occasional capability. Working near the limit also tends to wear consumables much faster. The figures depend on the maker, the material and the settings, so use the specification for your own equipment.

How can I tell that a nozzle is worn out?icon-minus-redicon-plus-red

Look at the orifice. A nozzle that is worn will often show gouging, or an orifice that has become oversized or oval instead of round. Cut quality warns you too: dross that settings changes cannot cure, a cut that wanders or leans, or a spray of metal along the top of the cut often point to a worn nozzle.

Inspect the nozzle and electrode whenever you change consumables and replace them as a pair when they show wear, rather than waiting until the torch stops cutting. Always follow the wear limits in your torch manual.

What eye protection do I need for plasma cutting?icon-minus-redicon-plus-red

The plasma arc gives off intense light that can injure your eyes and burn exposed skin. Manufacturers' manuals call for eye protection with the correct filter shade for the cutting current, such as a welding-type helmet or a face shield with goggles and side shields underneath.

The right shade depends on the current you are cutting at, so use the table in your cutter's manual or the shade recommended by your risk assessment. Wear flame-resistant clothing and gloves too, and screen the area so others are not exposed to the arc.

Can I rely on the cap safety switch when changing consumables?icon-minus-redicon-plus-red

No. Many torches have a switch that detects whether the retaining cap is fitted and cuts the output when the cap is loosened. It is a useful back-up, but safety devices can fail, so the manufacturer's instructions still tell you to switch the power supply off and disconnect it before handling torch parts.

Turn the machine off at its line-disconnect switch, wait for the power indicator to go out, and keep it off until the work is finished. Never defeat or bypass the safety switch in a torch.

How do I pierce plate without damaging the nozzle?icon-minus-redicon-plus-red

Piercing throws molten metal back up towards the torch, so the usual advice is to pierce higher and cut low: start the pierce at a greater height than the cutting height, then drop to the cut height once the arc has gone through. On a machine, the height control normally does this for you.

On thicker plate, start from the edge where you can, because piercing thick plate is hard on consumables. When you do pierce by hand, keep the spray directed away from you and the torch, and wear full protective gear. Use the heights and pierce limits in your torch's cut chart.

Why do my consumables wear faster on rusty, painted or perforated metal?icon-minus-redicon-plus-red

Dirty, rusty or painted surfaces make it hard for the main arc to transfer cleanly, and expanded metal or grating keeps interrupting the arc path. Each time the arc is lost, the torch has to restart the pilot arc, and the pilot arc is responsible for a large share of consumable wear.

Where you can, grind a clean contact point for the work clamp, avoid long pilot arc times, and expect to change consumables more often on this kind of work. Replace them before cut quality drops off badly.