Defective Freud Router Bit?

[Jerry Gilreath]

Uhhhhh, tell my ex-wife that! If you want her phone number, look on any truckstop bathroom wall. I'm sure it's there.

[Edwin Pawlowski]

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.

Ed [e-mail]

[Dave]

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 though.

Dave

[George]

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.

[Edwin Pawlowski]

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. Ed

[George]

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?

[Edwin Pawlowski]

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 depth. Ed

[LD]

----- Original Message ----- From: "Edwin Pawlowski" Newsgroups: rec.woodworking 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 for air. There are a lot of factors here, so I will spot you an order of magnitude. Still >200

Seriously? It goes to where there is less heat. Up the shaft, collet, pole pieces, windings... 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 the chip. 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 does enhance cooling. Or, maybe, whomever spoke to original poster was either uninformed or dismissive. Maybe it was coffee break.

[Edwin Pawlowski]

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.

[George]

Find an eighth-grader with his physical science book and review conduction/convection.

A physics text with computation might be a bit much for you until you get the concepts down.

[George]

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.

[Edwin Pawlowski]

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 involved?

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? Ed

[Edwin Pawlowski]

Fan? Oh wait, fan = spinning router bit. OK we do agree then.

[George]

Nope, I'm not grasping at straws, but standing on science.

[Tom Bergman]

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.

[Bay Area Dave]

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?

dave

Tom Bergman wrote:

[Bay Area Dave]

frickin' typos! make that, "Is that what you get when Delta Force meets Mr. T?"

dave

Bay Area Dave wrote:

[Charles M]

Dave,

I apologize for any misinformation there has been some about the reason for the gap in the carbide on your bit. It is correct that we put the gap there purposefully. The primary reason for this is that it makes the carbide seat more consistently. It also allows for the different heat contraction/expansion rates between the carbide and the steel body that occurs during and after the brazing process. Since carbide is brazed only on the flat back side and not on the edges there is not an issue of strength. This change will eventually take place on all of our bits.

Charles M Freud, Inc.

[John Crea]

And unless you are compresing AIR in confined space, "adiabiatic" does NOT apply here

John

[todd]

Well, I don't know what you're referring to, but all "adiabatic" means is that there is no heat transfer involved.

todd