Scraping the Surface With Abrasives – Some Basic Facts


Report by Peter Brett


When I was a kid, sandpaper was just about what it said on the tin – some gritty sand glued to a backing paper. It wore out so quickly that sanding was a chore and the amounts of the stuff I used was copious. In short, I hated sanding, even with the funny sanding attachment I attached to my Black and Decker Drill. But with the development of


ranges of sanding machines by power tool manufacturers, abrasives had to take on the challenge too. They needed to be harder and longer lasting as well as cutting more quickly too. There was a widespread, almost universal adoption, of various grades of aluminium oxide for use as the abrasive, including “humble” sandpaper used with a cork or wooden block. Aluminium oxide has the


advantage of being readily available, cheap and able to be processed in different ways to produce different grades of grit – from cheaper to more expensive – so that it can be suited to the market at which it is aimed. Backings and adhesives came


under scrutiny as well. Old paper style backings were simply not strong enough to hold the abrasive securely, so thicker and also more flexible papers became a necessity for “a decent sandpaper”. Making strips of abrasive years


ago usually involved simply sprinkling abrasive through a sieve-like arrangement onto a glued backing strip. The result of this was that the grit fell onto the strip and became glued in a particular way so that it cut only in one direction. Any sanding belts made this way had to have arrows on them to show a direction of rotation to accommodate not only the grit cutting direction but the join in the belt too. The most modern method now uses electrostatic forces to lay down the


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abrasive onto the belt. This means that the sharp ends of the grit point upwards and can be more evenly spread. The result is that the grit can cut in any direction and those minute, but annoying, troughs and peaks in the belt can be eliminated. I am sure that some old hands can still remember that odd sanding belt or disc that left scratches in the work because one piece of grit stuck out above all the others. It goes without saying that grit adhesives have also improved massively over


the years. Sanding is a process that produces heat, and this often caused the grit to fall off the backing. Modern glues keep the grit firmly attached to the backing despite a lot of heat being generated at the sanding point. But things don’t stand still with adhesives either, and there is currently a lot of work being done to develop a strong formaldehyde-free adhesive since formaldehyde is one of those “no – no” chemicals that some think we should avoid altogether. The development of orbital and random orbit sanders was the next big step


in the development of abrasives. As the sanders got better, there was need to find more efficient ways of attaching the sandpaper to the machine. Most sanders relied on sprung clips on the base to hold the abrasives in place, but I always found these clips hard to use and inefficient. A far better way was using hook and loop backings that gripped the entire sheet to the platen and often only let one down around the edges. Then dust collection became an issue – leading to sanders with sanding


platens with legions of holes all over them and a motor fan that drove the dust back into a dust collection bag. Some of these systems are remarkably efficient and are becoming ever more so, as power tool manufacturers aim to collect nearly 100% of all the dust from a machine at point of use. It really helps that affordable vacuum systems are now routinely used too. Clients simply don’t accept dusty sanding methods any more. Mesh backed abrasives have also hit the shelves in recent years. These have a


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grit bonded to an open mesh that allows dust to pass more freely into the dust collection system. My experience of these is that dust collection is very good, but the rims of the mesh disc tend to become very frayed if you run them up against edges whilst sanding. So, generally speaking we have good choice of abrasives now. Whether


DIYer, professional or whatever, we can find an efficient abrasive to do the job we want to a high standard. But we can be assured of this: - sanding machines are going to become better and the abrasives they use will have to develop and change as well. All I can say is that I am so pleased that I don’t have to use “old-style” sandpaper any more. Modern stuff is quicker, easier to use and readily available.


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