Ever come across a need to sand something and your regular assortment of power sanders just aren't the right tool for the job? If so, then you might be keen to check out the Blow Fly sanding attachment.

Designed by the same individual who came up with the Easy-Riser kit for drill presses (Piric Design), the Blow Fly sanding attachment was created to tackle a wide variety of sanding tasks, and as we will see, it is both inexpensive and very adaptable to other tasks too.

The Blow-Fly Sander
So what is it? Essentially, it is an attachment that can mount in your drill press or portable power drill. It looks somewhat like a large flap sanding attachment, and essentially it performs some similar functions. However, unlike some flap sanding attachments, the Blow Fly sander can use inexpensive, standard sized sanding belts you might buy for a belt sanding power tool. You can use virtually any length belt too with a width up to a maximum of 3 inches (75mm). It is recommended to use belts no coarser than 80 grit to avoid damaging the blow fly attachment itself during use.

As you can see from the image above and the photos to the right, the sanding belt is arranged in such a way to the body of the Blow Fly that six individual sanding flaps are created. This is the standard configuration, although you could even configure it for three larger sanding loops for more aggressive sanding tasks like removing paint or rust from metal. Full instructions are provided for how to disassemble the blow fly, load a new sanding belt and re-assemble the tool. The process is a little tricky to begin with, although it is still relatively simple, and once you have done it once, it becomes a lot easier in subsequent attempts.

One of the things I like most with the Blow Fly is that it not only uses standard sanding belts which are readily available and inexpensive, but you can move the sanding belt around to expose new flap surfaces and new grit once a particular part of the belt becomes worn through use. This makes using the Blow Fly very economical as you can get a lot of use out of a single sanding belt, particularly if you use it for wood sanding only - belts tend to get a little more 'torn up' in more aggressive tasks like rust and paint removal from harder surfaces or materials.

The Blow Fly works by wedging in parts of the sanding belt between a series of rods and a single contoured grooved body component, then securing it in place via the top and bottom circular disks and the top shaft. Avoid over-tightening the top shaft so the sanding belt is not damaged or distorted.

Using the Blow Fly Sander
Attaching the Blow Fly to your drill press or portable power drill is simple. It simply attaches like a regular drill or driver bit into the chuck and is tightened up. The shaft of the Blow Fly measures 12mm, so you will need at least a 13mm drill chuck to allow it to fit. Choosing a higher drill speed setting will give better results than using a lower speed setting. I found that lowering speeds in an attempt to slow down removal of material didn't work too well. You really need to keep the speed up high (at least 1000 RPM minimum) for best results, and if you wish to slow down removal rate, just use a finer sanding belt instead.

With the blow fly installed in the drill press and the machine in action, you basically present the workpiece to be sanded against the spinning flaps of the sanding belt. The flapping action will gradually remove material in a fairly consistent fashion. I achieved best results by moving the drill press table up close to the bottom edge of the sanding flaps to provide a solid surface to keep your workpiece referenced to:- hand-holding the workpiece is much harder. You could also make a jig/sub-table for your drill press table so that there is no gap between the bottom of the sanding flap itself and the drill table so you can sand all the way to the bottom edge of your workpiece.

When used in a drill press, the sander works well to sand rounded edges, curved forms, and even larger profiled edges. If you need a less aggressive or "softer" sanding option, you can actually use a knife or sharp cutting tool and slice the sanding flaps into smaller sections (see photo right). Doing this makes the belt flaps much less rigid and more able to get around finer details and into smaller coves etc. In fact, you can change the dynamics of the sanding action quite a bit by varying the number and location of cuts made into the sanding belt.

When mounted in a portable power drill, the blow fly can be taken just about anywhere. It is quite effective in removing flaking paint from most surfaces, and ideal for removing paint from old furniture or rust from metal structures or joins. Again, slitting the sanding belt makes it adaptable for a range of tasks. You can also mount scouring pads onto the Blow Fly and use it polish metals or plastics too!

The quality of the sanding belt does play a role in how well the Blow Fly works. Ideally, you want a good quality sanding belt with a tough, but flexible fabric backing that can take some abuse. I deliberately loaded up a cheap sanding belt I bought in bulk a while back for my belt sander and you can immediately notice the difference in the quality of the sanding, and the belt didn't stand up to the abuse I put on it as well as a more expensive, higher quality belt did.

Overall
The Blow Fly is quite a unique idea. It is a handy sanding attachment in a number of situations. It won't replace all the sanding machines in your shop by any means, but I see it as an excellent companion sanding tool to attack those sanding and stripping tasks your other stationary sanding machines are not well suited to tackling. As a portable device the Blow Fly comes into its own. Again, it's not unique in the fact that there are other products on the market that will perform similar functions but very few (if any) have the option to fit new abrasive materials - most times you need to go buy a whole new part when the abrasive wears away, adding to the cost. It is a larger attachment however, so you need to get used to the bulk of blow fly hanging off the end of your power drill, but it is not overly heavy and the larger surface area it offers (up to 75mm) is three times the size of many smaller abrasive attachments, so for large sanding tasks, you can get the job done in a fraction of the time.

I like the overall concept of the Blow Fly. I can't really see an easy way to further improve the changing of abrasive belts, which seems to be the only tricky issue with using it. But this design is what makes the product unique. At the retail price of around AUD$45, the Blow Fly offers much more flexibility than a large drum sanding attachment of similar size (and price) could deliver.

The Blow Fly will no doubt get regular use in my workshop and around the home for all those difficult sanding tasks not handled easily by other machines or methods. It's a handy tool to have!