the routers get occasional use but lately i discovered i avoid them just
because they are so noisy
i never thought about it until now and i cannot understand why they have
to spin so fast
5000 rpm should be plenty
what am i missing
On Wednesday, January 18, 2017 at 2:49:41 PM UTC-6, Electric Comet wrote:
Its really about the strength of the bit while cutting. Bits are commonly
1/4", 1/2", 3/4", 1" diameter and bigger. Smaller is weaker of course. Ev
eryone moves the router bit through the wood at roughly the same pace. Mor
e or less. The smaller bit, because it is weaker, has to take a smaller bi
te. Lets pretend this bite is one third as large as the big bit. (Pi at 3
.14 comes in here to get the bite of one third.) So it has to spin faster
than a large bit so when you push it through the wood at the predetermined
speed everyone uses, the wood all gets cut. If the small bit spun at the s
low speed of the big bit, then you the operator would have to push the rout
er through the wood at one third the pace. Doubt people are going to do th
is, so you solve it by speeding up the router speed.
Lets use your example of slow speed, or fixed speed, from the table saw. T
able saws all spin the same speed no matter how thick wood is you are cutti
ng. Cut 1/2" wood or 3" wood. Blade spins the same speed. I'll bet you p
ush the 1/2" wood through the blade much faster than you push the 3" wood t
hrough the blade. You manually vary the feed rate of the wood through the
fixed speed blade. You could do the same with routers by being 1/3 as fast
with the small bit compared to the large bit. With table saws you vary th
e feed speed so the amount of wood, thickness of wood divided by amount of
teeth, is the same over a given time period. You cut the 1/2" thick wood 6
times faster than you cut the 3" wood.
I'm guessing some engineer, scientist figured out the optimal cut speed, fe
ed rate, bit size, teeth number, etc. some time ago for router bits, saw bl
I do know this: I had a variable speed Ridgid router, and experiemented
with the speed. Once I hit 16,000 RPM, the cuts were happening very
nicely so I just left it there.
Is it the optimal for every material? Probably not. Is it more than
good enough for wood? Yep!
A mini archive of some of rec.woodworking's best and worst!
Put a router bit in the drill press and see how well it works at lower
rpm. Try it in a hand drill too. The bits are designed to perform at
high rpm and there is a lot of thought and design experience that
determine the cutting edge for best finish and chip removal.
I rarely use a hand held router as I have a table and lift that works
Please stop, it's embarrassing.
Do you even have a router and do you use it. I can assure you that not
only would 5000rpm be way to slow for the typical router bit, but it
would be more dangerous as well. You're much more likely to get
kick-back and jumpy action at slower speeds.
That slow of a speed is also going to give you a really crappy cut.
You think? Maybe get a variable speed router and do some test cutting
before you throw around completely unwarranted and uninformed opinions
I'm sure all the mechanical and electrical engineers who have been
designing and manufacturing routers and router bits for the past century
have no idea what they've been doing.
"Playing is not something I do at night, it's my function in life"
He does not understand tip speed. Small bits demand higher RPM's to
have the proper tip speed. 10" saw blades turn under 5K because the tip
is 10" from the center of rotation, so the tip is moving very fast.
C = 2 *Pi * d, where d is the diameter. Or, replacing d by 2r,
C=4*Pi*r~~ 12.52*r. In particular, C is a linear function of r. As an
example, if r=1/4" then 5000RPM corresponds to 3.14*5000000 inches
per minute, or 15000/60 %0 inches per second. I s'pose whether that is
fast, is relative. The length of the edge of the cutting bit, as well is
its shape, would seem to be important too. Intuitively, I would want to
cut a complex shape slower, but I suspect that is backwards
thinking--surely better to cut a complex shape by taking shallower
cuts. If all that the reader remembers is the previous sentence, they
may be well-served by this post.
I think you may have missed something in your calculations...
If your bit diameter is 1/2" the circumference would be 1.57 inches,
1.57" *5000 = 7850 inches per minute, and that = 130 inches per second
or about 7.4 MPH, way too slow to make a smooth cut.
Ideally and if a 1/2" diameter router bit could withstand being spun
this fast, 50,000 would be the idea cutting speed. The tip speed at 50K
would be 74 MPH and or about the same speed as a 1" diameter bit
spinning at 25K.
I am not sure what you are trying to say here and understand that you
have corrected part of you equation in another post.
I appreciate the effort.....
The speed at which the tip of a cutter strikes wood is important within
a specific range. Too slow and the cut ends up rough, maybe splintery,
and maybe stall the motor.
Feed rate has little to no effect on the optimum cutting speed other
than taking small bites typically yields a flatter result with a router
bit. Feed too fast and you get bigger bites out of the wood and smooth
scallops, too slow and you get flatter results and maybe burn marks.
The proper feed rate for any given tool is something a woodworker has to
learn by practicing to get the best result.
Anyway the typical 10" saw blade has a tooth tip speed
of approximately 104 MPH, assuming 3500 RPM
A 1" diameter router bit has a tip speed of
approximately 74 MPH, assuming it is spinning at 25000.
I think ideally router bits in this size range and smaller should spin
faster but this becomes dangerous. Typically 2 or 3 cutting tips are
removing all of the wood, compared to a 10 saw blade with a tooth doing
1/10 of the amount of wood as the router bit.
Go up to a 1.5" diameter router bit and slowing the speed down to 18000
RPM and you get a speed of 80 MPH.
Go up to something like a panel raising bit that is 3" in diameter and
the speed should be reduced to about 12,000 for a tip speed of 107 MPH
On 1/18/2017 6:54 PM, firstname.lastname@example.org wrote:
Actually, smoothness of cut is what it is about. The faster the speed
the more cuts with a given speed.
Many routers have fixes single speeds.
Actually many TS do not run at the same speed. The larger the blade the
slower they typically run. Again, tip speed. A number of miter saws
spin their blades even faster that a TS and typically have more teeth
than you commonly see on a TS.
If you are saying the TS's are not variable speed, that is close to
true, Shopsmith's have variable speed, but should be run at a suggested
Cut 1/2" wood or 3" wood. Blade spins the same
Except when it does not. Under ideal conditions the blade maintains its
speed but time and again under powered saws spin slower when cutting
thicker material. Hence think kerf blades.
I'll bet you push the 1/2" wood through the blade much faster
You learn to not do that to get smoother cuts.. Smaller bites normally
mean smoother cuts.
You manually vary the
Really? 6 times faster? I go the same speed regardless, I strive for
smooth cuts. Fast feed rates result in a cut that is less smooth than
slower feed rates.
Yes and I doubt any would agree with your thoughts. While your comments
make sense to some degree. The results yield less than the best outcome.
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