The last time I used a wallchasing machine was about eighteen years ago, and even now, I remember it as a very unpleasant experience.  The task was noisy, dusty, dangerous, but still easier than using a cold chisel to cut a channel in the brickwork.
But Health and Safety has caught up with wallchasing machines and while it is still a noisy job, the experience of using such a machine is a much safer and less dusty one these days. I guess that some of the improvements have been made possible by the invention and wider use of diamond blades, but a quality machine always makes a difference.
 A couple of editions ago I reviewed another FLEX machine, the Giraffe Wall Sander and was very impressed with the quality of its construction and design. The FLEX wallchaser (I love the German word for it – mauerschnitzer - literally wall slicer.) is similarly well-designed and constructed as we have come to expect from many German tools these days. This may have something to do with the fact that the FLEX company makes a range of trade and industrial quality sanders, grinders, mixers and surface finishers, and so, are expert at what they do.
 Releasing the wallchaser from its large custom-made case is an indication of the sort of thing one can expect from this machine – the case is large enough to hold all three metres of power cable comfortably. There are a few spaces for an alternate dust extraction nozzle, a cold chisel, the auxiliary handle and spare diamond blades. All the bits fit in and don’t rattle around and the case catches, while simple, hold the whole thing together safely.
 A close examination of the body, the motor casing and the cutter cover reveals robust construction, but also well-finished quality. There are no sharp bits on any extrusions or castings. Key pieces, like the motor gear housing and the cutter cover are made from strong alloy castings that are meant to last. On the other hand the guide base is made from 2mm or so thick bent steel. This is pop-riveted to the guard and is clearly meant to be replaced as it wears after (many hours) of use. So far, so much as standard it seems for FLEX machines. Robust construction is an absolute necessity for a wallchaser, that will, by definition have a hard working life.
 But the things that really impressed me and the things that will make it a real timesaver on the building site are carefully thought out design features that I have not come across in similar products.
Firstly, it is possible to use this machine, change cutters and adjust it in a variety of different ways without using any tools at all. This is a huge advantage, as anyone who has ever fiddled about with a hex key or spanner on a cold winter’s morning, trying to fix or adjust a recalcitrant tool will know.
For example, to replace the cutters on similar machines would probably involve at least one spanner, perhaps the complete removal of the cutter guard assembly and maybe a bit of swearing. With the FLEX, coming as a complete novice to the machine I was able to adjust the width of the cut on the blades in about four minutes flat with my bare hands and on my lap. Admittedly, I had not yet used the wallchaser in anger, so it was not clogged with brick dust. The front part of the alloy cutter guard is released by turning a big lock handle 180 degrees. This releases the guard that can now be lifted off vertically. The cutters are revealed completely, along with the large milled-edge quick-release clamping screw.
Simply push down the spindle lock on the gear casing and untwist the clamping screw and the blades are released and ready to be adjusted or replaced.
Putting it all back again is the reverse, but you have to remember to depress the body of the unit so that the guard hood can link to the base unit. 
The above is such a sound and useful piece of design, and I think, such a key feature that the FLEX wallchaser could sell itself on this feature alone. But, as is often the case, if one part is well designed, other parts are too – making for a piece of equipment that is a simple to use, and therefore a valuable piece of builder’s kit.
A quick run over the other switchgear will confirm the theory. The on/off switch is a large positive slider switch. Easy to lock on and easy to turn off. The spring-loaded cutter release button has effectively two ways of operating. If the operator prefers it can be pulled from the bottom with the index finger to release the plunge mechanism. Alternatively, the thumb can be used to push the top of the catch in to achieve the same thing. Either way it is very convenient and safe. Because the switches are big enough too, they can be operated with a gloved hand.
On top of the alloy cutter guard is the dust extraction turret. I call it this because it sticks out as prominently as a gun on a tank. This is a strong plastic construction with a ribbed, rubberised top for easy gripping and protection. It swivels around a full 360 degrees, so dust collection via a connected industrial vac can be adjusted for safety and convenience.
The depth of cut is set via a mm marked scale on the front of the machine. A plastic stop is simply moved up or down the stopped arc.
Finally, and this is another feature down to excellent industrial design, is the moveable motor. By pulling a toggle switch near the gearbox casing, the motor can be moved nearly 180 degrees towards the front of the cutter guard. This allows the cutters to be brought as close as possible to the top or bottom of a cut channel because the motor can be moved out of the way. It saves effort and makes for a neater overall job. 
You can see that even before I started using the FLEX “mauerschlitzer” I was impressed with its construction and design. In use it didn’t disappoint either. The motor is powerful, the diamond cutters do a good job on most building materials and with the correct type of vacuum attached, the amount of dust collected is phenomenal. (It is still essential safety practice to use ear, eye and dust protection though)
If I were doing wallchasing on a regular basis I would demand to use a machine like the FLEX as a matter of course. My guess is that many other similar machines would disappoint me because they are not designed and built to the same standard. What a “mauerschlitezer!”