True, but once the water carries the heat to the radiator, you need airflow
to remove the heat from the water. Try eliminating the airflow. Or you
need one hell of a water tank to absorb all the heat.
Point is, there are more efficient means of heat transfer. In the case of
the router bit, metal-to-metal is by far more effective than air, and with
no flow-through provisions, I fear the only thing blowing smoke here is the
rep the OP spoke with.
More efficient, but there is a limit. My point is that no one can criticize
the idea unless they can back it up with facts. I've not seen any.
The cutting edge build up heat and transfers it to the shaft. The shaft
heats up and transfers it to the router. There is a maximum amount of heat
it can absorb in a given time and once that is reached, the cutting edge
will overheat if friction continues to heat it. If two spots are enough to
reach the thermal capacity of the heatsink's ability to absorb it, other
means may then become more efficient to dissipate the heat. Maybe air flow
will help. I honestly don't know, but I'm not going to deny Freud's claim
unless I could prove it was BS.
Nice point, but don't push the second paragraph too close to the cliff, it
won't fly. Heat sunk into the metal flows out of the metal at a distance.
Greater warmed surface, greater outflow. Also, trapped air pockets don't
cool. Regardless the usability, the reason given is BS. Probably saves a
dime a dozen.
Wonder if they whistle?
I'd be willing to give it a shove off the cliff. At least until someone
comes up with a real fact, real numbers. Heat flows out to where to? At
what rate? What is the temperature rise? Why do they put cooling fans on
computer chips and auto radiators? You can still build heat at the source
if the sink cannot absorb it fast enough.
I'm sure you'll never agree, but neither will you come up with a fact
showing heat buildup and flow rates.
Maybe they can make them whistle and change pitch if you cut at the wrong
----- Original Message -----
Sent: Tuesday, March 02, 2004 7:09 PM
Subject: Re: Defective Freud Router Bit? - Response from Freud
The coeficient of thermal conducrtion for steel is approx 2000 times that
There are a lot of factors here, so I will spot you an order of magnitude.
Seriously? It goes to where there is less heat. Up the shaft, collet, pole
Routers have a fan in the housing. Eventually heat is radiated or conducted
into the surroundings,
Then into the universe.
The fan isn't on the chip..The fan is on the heatsink and the heatsink is on
Most AMD chips will self destruct in seconds without a heatsink, DAMHIKT
That auto radiator arguement is not applicable (it doesn't hold water :-)
Exactly! Greater contact area yields more rapid heat transfer.
I did not intend to impune Freud products, management or their families.
I own a few F bits and blades. They perform fine
Maybe the new weld contact actually has a greater cross section and really
enhance cooling. Or, maybe, whomever spoke to original poster was either
uninformed or dismissive. Maybe it was coffee break.
Sure, but along the way there are non-mettalic parts that do not transfer
the heat very well and the heat will build up at the source if it is not
carried away fast enough. Routers are made to spin its, not cool things.
Right, but the heatsink alone is not capable of doing the job, thus the
cooling fan required on many chips. Same with the auto radiator, even
moreso. The water is the heatsink, but it cannot take the heat away from
the engine fast enough, so it is assited by air flowing over a radiator.
Eliminate the air and you need a larger mass of water. Air Cooled ingines
have limits for the same reason.
My point in this was that you can't just make blanket statements that Freud
is wrong unless you can back it up with fact applicable to the particular
situation. It may be pure BS, but neither of us had actual measurements to
prove them right or wrong.
And without the white goo, nothing works! Just that little bit of "air"
slows the transfer.
Oh yes, the fan is necessary precisely because air, with its lower (and with
heat, lowering) density can't remove the heat available from the metal
quickly enough with its widely-spaced molecules, and requires a fresh supply
from the fan.
I read the book. Show me the figures proving that in this particular
situation that heat dissipation it better with solid versus vented. I've
not seen one number from you proving that there is enough mass to dissipate
the heat properly. I've not seen your computation on this particular
situation and until I do, you're just blowing hot air.
I'm not disputing that metal conducts better than air, but if the metal
reaches its capacity and you can't add more metal, the gap is not a
hindrance. You are not able to carry through the entire equation. Did you
do any testing? Do you know what temperature and specific heats is
You brought up the book on physics, but you've yet to provide real facts to
support the router bit heat transfer information. What numbers do you
suggest we use for the calculations?
I will hypothesize a completely contrarian argument to what's been
constructed so far. One could argue that the ideal bit would have NO
heat transfer between the carbide cutter and the body. In such a
design, the carbide would more quickly heat up to it's stabilization
temperature, i.e., the temperature at which it dissipates (largely
through convection, spinning through the air at 20,000 rpm, I would
guess convection doesn't amount to diddley-squat after the first
couple minutes) the same amount of heat it generates. While the
temperature of the carbide may be higher (marginally after a few
minutes as compared to heating the entire bit imo), the temperature
gradients throughout the carbide would be smaller. This would result
in more even thermal expansion of the carbide, better retention of the
profile, probably reduced vibration, and potentially less stress at
the carbide/braze and certainly the braze/body interfaces created by
the thermal expansion (or least a more even stress).
With the heat sink model bit, there will be a relatively large delta T
between the carbide cutter and the shaft, as compared to the preceding
description (the delta T across the carbide will be very small,
although the T will be higher), thus you have all kinds of differing
thermal expansion rates and corresponding stresses induced.
Now I can speculate that the ventilated router bit, aka the Freud
model, is a reasonable compromise given you need to braze the
carbide, and all such materials have high thermal conductivity as
metals (and sufficient flexibility). By increasing airflow behind the
carbide (although how they keep it filling with crud is beyond me) you
reduce the heat transfer to the bit by lowering the temperature of the
carbide and at the same time reduce the T of the carbide overall
(although I'd think you'd have higher stress than the adiabatic
interface model first described).
Or it could all be cost-saving BS.
ah, yeah, what Tom said...I think...or not. What DID you say, Tom?
That Freud knows what they are doing? :)
I love those 50 cent words like "adiabatic"! "Delta T" is a great term
to sprinkle around from time to time. Is that when what you get when
Delta Force meets Mr. T?
Tom Bergman wrote:
Sounds as if what Freud did is eliminate the need for a precisely machined
face to mate to the carbide, if we can believe the "representative's" post.
Could be good, could be bad, but we know it doesn't cool anything but the
price of manufacture.
After the heatsink is sunk where does the heat go? Why would not increased
air flow not make a difference? What is the actual heat flow across the
section that is welded versus the open area?
Seems as though we are dealing in supposition and have no facts to back up
anything. Could be BS from Freud as cost of welding is reduced, but than
again, they may have spent a million bucks doing sophisticated testing.
Until I see numbers on one side or the other, I'll keep an open mind.
Could be BS from Freud but I find it unlikely that a manufacturer,
which has built a reputation for producing primarily high-end tools,
would eliminate 1/8 of an inch of brazing to reduce cost; while
sacrificing quality, performance, and consumer safety. I also find it
unlikely that this decision was made without any testing whatsoever.
I mean do you really think someone was sitting in the board room of a
mulit-million dollar corporation one day and just said: "I have an
great idea to reduce the manufacturing cost of our router bit line,
let's give it a go without conducting any safety or performance
research - whatcha guys think?" I could be wrong, just my opinion.
I would be interested in hearing from someone who purchases a newer
lot 5/16 radius roman ogee bit to see if it has the same type of weld
wrote in message
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