BOSCH 3725DEVS: Variable speed and smooth start.

Home projects are the perfect excuse to buy power tools. Almost every "man" of the house knows what the Home Depot advertisement is all about, even if the tool ends up with little or no use. Regardless, DIY projects help reduce cost significantly and the purchase of a specific tool is often warranted with a single use.


APPLICATION

Let's just say we just bought a house with a kitchen that has honed granite counter tops and you really like it to be shiny. Well, most granite places will tell you that we would be best of to buy a new slab. Somewhat true, but not necessarily in our interest. It turns out that a well kept secret is that you could do it on your own with the right tools and some skills. There are wet polishers which are so specific that home usage only barely justifies the purchase.

The usable diamond polishing pads, however, come in two varieties Wet and Dry. The latter often tolerates both conditions while the wet pads require the presence of a cooling fluid. Anyway, this is where the Bosch random orbit sander came in since the variable speed allowed to get as low as 2800 rpm (diamond polishing pads are typically rated below 4500 rpm) while most low budget sanders are set to a fixed 12,000 orbits per minute. In other words, the Bosch was suitable for the job and still flexible enough to be universal in application (i.e. upcoming woodwork projects).


DETAILS

Ergonomics: [****-] The most typical application might utilize the pal rest which allows to use the Sander in a natural way which still sometimes requires to use the handle to reduce rotation. The power switch and the speed adjustment are in a logical position for usage with the handle (rather than palm rest), but are only needed to start and stop anyway since the switch also provides a lock to keep the polisher running. Vibration is moderate during start-up and relatively low once up to speed. This of course heavily depends on how centered the polishing pad is and how "grippy" it is relative to the polished surface. The front palm rest has to be assembled upon first use and works best in conjunction with the handle for maximum control. It can be removed via a single screw for tight areas.

Flexibility: [****-] The variable speed makes this device usable for a variety of tasks. Both dust removal method and electrical protection grade require a dry environment to prevent damage to the machine and most importantly safety hazards. (Wet polishing is not a good idea with this one!) Anyway, the 5" discs are widely available with and without the 8-hole configuration (dust removal) and virtually any Velcro backed disc of that size is likely to fit without problems. (In my case, the 5" diamond resin polishing discs fit without a glitch, but of course won't provide the holes.) Unfortunately there is only a soft backing included and the hard disc is optional.

Control: [****-] The handle is well sculpted and the machine is easy to hold and guide once up to speed. That can be anything from 4,500 opm to 13,000 opm (orbits per minute). While that's electronically regulated, the overlaying rotation is heavily depending on pressure applied to the machine. That may be the reason why Bosch doesn't rate that, but it's certainly way less than the rated orbital speed and the resulting surface speed may be greatly reduced relative to the implied speed by the orbits. This technicality aside, the soft start feature and overall ergonomics make it easy to keep the device under control. However, it can be fairly unstable when placing the disc off center and running at a high speed. Physics won't be cheated.

Dust: [***--] It's a dry polisher, so it's just fair to say that it will generate dust, and lots of it. It has become a common feature to provide a collection which typically sucks parts of the dust into a chamber. However, it requires compatible polishing pads to expose the 8 holes that sign responsible for this task as they lead directly to the work surface for efficiency. The feature does not extend to the surrounding of the disc and ultimately only reduces dust but cannot eliminate it. Worse yet, with discs that cover up the 8 holes it's basically turned off. Anyway, the reduction is noticeable for normal woodwork with standard discs. The associated cleaning of the filter, however, is relatively frequent and may render it a bit useless or at least slow down the work flow. I am not aware of a vacuum attachment, but it may be available as an accessory.

Durability: [****-] Given that it only has one major project done so far, but build quality and overall stable performance indicate that this is going to last for a while. Granted, I am not using it every day and you probably not even call it light duty. Either way, I will update as more data becomes available.

Value: [*****] At $140.- this device is one of the cheapest sanders that offer both variable speed and compatibility with 5 inch discs. It's hard for me to judge its value for a professional workshop, but build quality and overall handling are very good. It's easily suitable for medium duty and a great deal in that regard.


© 2008, theuerkorn


Note: It's easy to get confused between opm (orbits) and rpm (revolutions), but in regard to a polisher it just means that orbits randomize the motion on a much smaller level than revolutions would. The resulting polishing speed is consequently much less for 4000 opm than it would be for 4000 rpm (circumference). That naturally results in rpm being much more "aggressive" (or effective) for polishing than opm, whereas orbits ensure the smoothness or random motion.