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Fits Nozzle Mix Torches with flat tubes. Maximum 300mm radius.
Practical answers on using circle cutting guides and roller guides to get cleaner, more accurate gas cuts.
The distance between the nozzle and the plate controls how well the preheat flames and cutting oxygen work together. If the nozzle is too close, you get grooves and deep drag lines because part of the preheat flame burns inside the cut and deflects the oxygen stream. If it is held too high, the preheat loses effectiveness, the top edge becomes rounded or beaded, and the face can be slightly bevelled.A guide that keeps the nozzle at a steady height removes one of the hardest things to do freehand. Set the height to the torch and nozzle maker's recommendation, then check it again if you change nozzle or plate thickness.
You normally pierce the plate first. Heat a spot inside the circle until it is at ignition temperature, then open the cutting oxygen gradually and hold the torch steady until the jet goes through. Slag and molten metal can build up and be thrown back at the nozzle, so follow the torch maker's piercing method and wear full eye and face protection.From the pierce hole you cut out to the line of the circle, then use the guide to cut round it. Piercing is slower with propane than with acetylene, and thicker plate takes longer to pierce, so allow time and do not rush it.
It can. Propane has a lower flame temperature than acetylene, so piercing the start hole takes longer, although cutting speed once under way is about the same. Propane also tolerates a greater nozzle-to-plate distance, which reduces the risk of molten metal splashing back onto the nozzle and causing a backfire.The nozzles are different too. Acetylene and propane need nozzles designed for the gas, so make sure the nozzle in the torch matches the fuel gas, and set the guide height to the maker's advice for that nozzle. Check the instructions for your torch before changing from one fuel gas to the other.
A circle cutting guide turns the torch into a compass. A pointed pivot pin sits in a centre-punch mark at the middle of the circle, and the torch head swings round it at a fixed distance, which is the radius. Cutting a clean circle freehand is very difficult, even for experienced operators, because you have to follow the line by eye and hand.Using a guide means the radius stays constant, so the circle is more accurate and the edge is smoother. A roller or similar support at the torch end usually carries the weight and helps keep the nozzle at a steady height. You still pierce a start hole and control the cutting speed yourself.
