Basic
Rules of Thumb for the Router
By David Fielhaber
Safety
Most people know the common sense approach to power tools, but
they don't always follow them. People get excited or in a rush
or just plain forget. I know because I have done all three. There
is nothing quite like a runaway router bit or a kickback of wood
to get your attention and remind you of an error in judgment.
Routers spin very fast and have a lot of power, so you have to
take a few precautions to make sure your fingers and vital fluids
stay where they belong. You know them, but it doesn't hurt to
remind yourself the easy way instead of the hard way. This list
is not complete but it is a good start.
- Safety glasses - Don't leave them lying
on the bench, put them on and keep them clean. You can't see
your marks if they are full of dust, and you wont see anything
if a wood chip damages your eye.
- Sleeves -Wear short sleeves or roll up
your long sleeves above your elbow. This isn't as big an issue
when using the router hand held, but more so when it is mounted
in a table. It only takes a second to reach across the spinning
bit and your sleeve is caught and pulls your arm into the bit.
- Unplug the router when you change bits.
It's a bit of a hassle but while your wrestling with the router
and wrenches you could bump the switch. At this point your fingers
are the first to suffer, as the wrenches become projectiles.
What happens afterward is anybody's guess.
- When you tighten down the collet, make
sure you have 80% or more of the shaft in the collet and that
you have tightened it securely. 1/4" shafts can bend if
they are out too far, and when they do you will damage the material,
the bit, the router and possibly yourself.
- Periodically check the condition of your
router bits, especially if you drop one on the floor or bench.
Inspect the bearings, the brazing and the carbide. A piece of
carbide flying off at 22,000 rpm is not a nice thing.
- Nobody reads the owners manual. It's boring,
but every tool, every brand and every model is different. It
only takes a few minutes to read through and can save you time
in the long run and help to avoid an injury. Besides, then you'll
know what that one mysterious knob on the side does.
Feed Direction
The rule of thumb for feed direction is
if you are facing the outside edge of your stock you want to move the
router from left to right or counterclockwise. If you are routing the
inside edge, such as the inside of a frame, you want to move right to
left or clockwise. In both cases you are moving the router against the
bit rotation direction. This action keeps the router pulling into the
material. If you move the router in the same direction as the bit rotation,
the router will tend to ride outward and try and run away on you. One
final suggestion is to start your edge routing on end grain, then with
the grain, end grain and finally with the grain. End grain has more of
a tendency to chip as you are finishing the cut so by using this sequence
you will have a better chance of avoiding any chip out.
|
Outside Feed Direction
|
Inside Feed Direction
|
Feed Rate
There are two things to remember
with regards to the rate of feed. The first is to keep the rate
as constant as possible. Before you begin your pass, whether
using a router freehand or on a table, place yourself so you
can push either the router or material in a fluid constant motion.
Each time you stop during a cut you have more chance of causing
a burn or a wave from pressure change. These can be sanded out
but it can be very difficult and time consuming depending of
the species of wood. The second is to adjust your rate of feed
to the species of wood you are working with. Generally speaking
the softer the wood the faster the feed rate and visa versa.
So you would be able to feed fairly quickly on some pine, spruce
or fir, but on oak, maple, or walnut you would have to slow down.
Router Speeds
The rule of thumb here is the larger
the bit or the harder the material, the slower the speed. With
the bit diameter, you have to keep in mind that the outside edge
will be moving faster than the speed indicated. You may think
it won't be as effective by slowing it down but the cutter is
still moving fast enough to provide a clean cut. Don't forget,
most shapers rotate at 10,000 rpm or less. If your bit is less
than 3/4" or 1" you can use the full speed of your
router (approximately 22,000rpm). For those bits between 1"
to 2-1/2" reduce the speed to approximately 15,000 rpm.
For bits larger than 2-1/2" use approximately 8,000 rpm.
These speeds are just to give you a starting place. Adjust them
according to the particular bit and material your working with.
For those with single speed routers, you just have to reduce
the rate of feed.
Shaft Diameter
Rule of thumb on shaft diameter
is if the diameter of the cutter head is 3/4" or smaller
you are safe with a 1/4" shaft bit. Once a cutter is larger
than 3/4" it is too heavy and creates too much force to
be safely used on a 1/4" shaft. There are large router bits
like style and rail bits available which have 1/4" shafts.
If you look at the weight and the amount of wood they are removing
you realize the amount of force placed on that shaft and the
heat, which can build up. I have seen these bits bent at 45 degrees,
and I don't like them. Generally speaking, if your router accepts
1/2" shafts buy all 1/2" shaft bits. The cost difference
is usually small and the safety advantage is large. If your router
only accepts 1/4" shaft bits try and stay away from the
larger bits until you can upgrade to a larger router. If you
do use a large bit with 1/4" shaft, pay attention, reduce
cutter height per pass and slow the speed and feed rates.
|
