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How to Cut Flexible Ducting

Aluminium flexible ductwork

In order to ensure a system is performing at its best and in order to provide the perfect conditions, you need properly-installed ductwork. The ducts must be specifically designed and cut according to the necessary sizes and formed so that they do the job and do it efficiently.

Two of the main types of ducting are rigid (spiral ducting) and flexible ducting. When it comes to flexible ducting, there are a number of variations. There is PU flexible ducting, PVC coated aluminium (combi flex), standard aluminium, aluminium insulated flexible ducting and many more. Rectangular ducting is available but is not as common as it is not as efficient and has a limited number of uses.

Flexible ducting is a widely preferred option for HVAC as it provides more flexibility during installation. In this article, we’ll look into how to cut flexible aluminium ducting. We’ll go through the steps and explore the process in detail.

How to cut flexible ducting

Before we go into the cutting process, remember that there are a wide range of different flexible ducting types and a diverse set of different cutting methods that you can choose from. Don’t forget to get your safety glasses and protective gloves out. Arms should always be held in parallel position, do not cross arms while cutting.

Depending on whether you’re dealing with flexible plastic ducting, flexible metal ductwork, or other types of ducts, the cutting process will vary. Before you start cutting your ducts to size, make sure you are aware of the type of ductwork and the recommended cutting methods for the material.

For starters, it’s worth mentioning that aluminium insulated flexible ducting is constructed of a wire coil and thin, aluminium layers that are protected by fibreglass insulation. If you need to cut the wire coil, it’s best to use wire cutters or alternatively tin snips. You can use a duct knife or utility knife to cut the delicate aluminium and the insulation that you’ll find inside the layers of the flexible duct. To secure flexible ducts to metal duct collars and to tighten j-clips around the duct you may need a screwdriver.

Flexible metal ductwork

For galvanised flexible metal ductwork, use tin snips based on the cut type. You can also use an angle grinder for the process. As angle grinders have a lot of different disc sizes, note that it’s important to choose the appropriate size for the particular duct. Compound snips with offset handles are a great choice if you want to have better leverage while thinner cutting blades are ideal for cutting thick seams, straight lines, and achieving curved sections. If the final result you want to achieve is a long straight cut, try using a snip with a large handle and thick blades. These are usually the older, traditional types of snips.

Use a felt-tip marker to pinpoint where you want the line to go through on the sheet metal. Make a tiny starter hole using the blade of a screwdriver. Start from the hole and cut down to the line. Afterwards, start cutting the line surrounding your round duct or rectangle opening on a straight duct.

If the seams are thick metal sheets, cut through them using compound snips. Position the seam where the snips’ jaws are and push. If compound snips are not enough, you can try using a hacksaw. If there are special cuts that you need to make, use special offset snips. If the number of curves you need to make are too many, use green and red-handled snips to separate which ones are left and which ones are right. If the cutting project only requires a few cuts, use the regular yellow-handled compound snips.

If you’re working with semi-flex ducting, the cutting process will be different. Place a rubber band around the duct where you want the cut and leave some additional space available for any imperfections at the end. Locate the area for cutting with a line using a marker. Use a hacksaw to create the cut and follow the line as precisely as possible. It’s also helpful to use tin snips for finishing the cut. Eliminate any flaws by filing the cut end and turn it into a perfect square.

As with any ductwork installation, please make sure this is carried out by a competent person and health & safety guidelines are followed at all times.

We hope that the information we’ve shared with you will help you with your next flexible ducting installation. If you feel that your ducting is in need of adjustments and customization, you can take advantage of our specialists’ experience and professional background. Get in touch with Ducting Express and we’ll help by answering your questions and providing you with the necessary information or support.