Originally Posted by BobandRick
It's good to see the tips are being noticed... 1/2" shanked bits have more mass than the 1/4" bits and with mass comes the ability to dissipate the heat build-up allowing the router bit to stay sharper longer.
Here is something to think about
: "Making Tungsten Carbide
Tungsten and carbon powders are blended and carburized in a furnace at 2700 - 2800 F. This produces the WC grains.
These grains are combined with Cobalt powder and mixed in a ball mill. Tungsten carbide balls are mixed with grains allowed to run for several days to get even dispersal of the grains and the cobalt powder. This powder is then dried and wax is added as a binder. The wax holds the powder together and makes it somewhat slippery so it presses into shapes well. Typically 15 to 30 tons of pressure is used to form the carbide into a tool shape such as a saw tip. The parts are typically pressed one of three ways. They are rammed in a mold before sintering. They are isostatically pressed. Isostatic pressing means they are surrounded by a liquid or a gas and the pressure is applied to the liquid. This transfers the pressures to the surface of the parts uniformly. The third pressing method is hot pressing during sintering.
The shapes are presintered in an atmosphere-controlled furnace at temperatures of 1,000 - 1,500F. The wax melts out and leaves the pieces sort of like a soft chalk. These chalk pieces can be easily machined although they are also easy to break and can be chipped here if handled improperly.
The final step is another sintering step that can take place in a special atmosphere, a vacuum or both. The temperature is typically 2,500 - 2,700 f.
During final sintering the parts will shrink up to 15% in any dimension and up to 35% in volume. "
I have a feeling the heat issue is not going to hold up as a major issue in 1/4" or 1/2" shank court. At least in my opinion. I should also point out that carbide is often attached by way of welding or brazing both in the high heat areas compared to woodworking.
My guess is if they last longer it is in the vibration/deforming areas. But hey what do I know?