ting edge will lose its sharpness. Second, the heat generated by a bit that's spinning too fast can cause burning in the cut.
SLOW DOWN. The solution is to slow down. And that's what a variable speed router allows you to do. A slower cutting speed can result in a smooth, burn-free cut that's safer for the operator, and easier on the bit and router.
It may sound odd, but using larger or even "standard size" bits at slower speeds can give you a much cleaner cut. The photo at right shows how burning can be controlled by just reducing the speed of the router. Vibration is also the enemy of a smooth cut. The faster the bit is turning, the more vibration you're likely to have. Slower speeds mean less vibration and better results.
WHAT'S AVAILABLE. In the past five or six years, the number of variable speed (VS) routers on the market has skyrocketed. AH of the major manufacturers now offer at least one model with this option.
When you go looking for a VS router, you'll find two different types. Most manufacturers use an infinitely variable system (left photo above). You can think of this as dial-a-speed. Simply turning a numbered dial on the top of the router allows you to increase or decrease the speed. But the actual speed you're getting involves a little guesswork. So some models have a chart, like that shown in the left inset photo above, that tells you what speed the numbers on
Chart shows relationship of numbers on dial to speed
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The second type is far less common and gives you the choice of several pre-set speeds. The Porter Cable 7519 shown above has a linear switch that moves between 10,000, 13,000, 16,000, 18,000, and 22,000 rpm (right inset photo).
BELLS AND WHISTLES. A couple of extra features you'll find on variable speed routers are the result of modern electronics. Most, but not all VS routers incorporate an electronic feedback system. It continuously monitors the speed of the router and supplies more power when necessary to maintain constant rpms. The upshot is that the router won't bog down.
Soft-start is another feature you'll commonly find on variable speed routers. It's intended to make hand-held use a little friendlier by eliminating the "kick" of the router when you hit the switch. If you're not familiar with this feature, you might think there was something wrong with the router the first time you turn it on. The router motor starts slowly and gradually revs up to full speed.
EXTRA COST. One of the surprising things about the variable speed feature is how little it adds to the cost of a router. Generally, the difference is not more than $10 to $25. For a tool you might have in the shop for many years, this could be just a drop in the bucket.
RELIABILITY. Finally, what about the question of reliability? Any time you add parts to a tool, you have a better chance of something going wrong. But the technology used here is pretty basic by today's standards and several product managers I spoke with assured me this hadn't been a problem.
All in all, the arguments for variable speed routers seem to outweigh those against. For only a little extra cost, you're giving yourself a lot more options. ESS
Eliminating the burning in a cove cut (upper example) can be as simple as dialing down the router speed, as in the lower example
Worth a Look: Speed Control Unit
If you own a perfectly good fixed speed router, but would like to have the option of variable speed routing, the router speed control shown at right might be the answer. This inexpensive unit (mine cost $25) works with most brush-type router motors (not with soft-start) up to 3V4 hp. It incorporates the electronic feedback feature described above and is fused to protect against overload.
To use the speed control, you simply plug your router into the unit and the unit into a wall outlet. The switch (at top) gives you the option of full or variable speed.
This unit isn't nearly as sensitive as the speed control on a router and I noticed some power loss at the top end. But if you're only going to do occasional variable speed routing, it makes good sense.
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