While I do agree the HP ratings of a wood router are wildly different you really should be running close to maximum spindle speed when using a single flute cutting tool. The other issue with wood routers is the Variac variable speed control means you loose a ton of torque when you turn down the speed. A proper three phase spindle+VFD even without a encoder has closed loop functionality (even in “open loop” mode) that will try to maintain a constant speed since it can measure back-EMF.
Yea, certainly didn’t mean to make that sound like “anyone running high speeds is wrong”, but I think there are instances where lower speeds can be beneficial too.
I’ve been running a 3/16" Amana O flute for awhile and found it to be a reasonable compromise between rigidity, minimum radius on parts, etc.
The manufacturer recommends 600-1000 SFM, which is roughly 12k to 20k, and I end up running ~15k (half of my 30k spindle) at the lower end of the recommended chipload. I found a pretty big performance increase being able to cut at full sheet thickness (0.08 to 0.125 Al5052), and unscientifically “seems” to work a bit better with the 3/16 bit than the 1/8" bit. Also, while a minor thing, we directly drill to 3/16 for our hole patterns, so it saves a collet swap to go from a 3/16 bit to a stub length drill bit.
To expand on the “unscientific” stuff… the 3/16" bit has at a slightly slower speed has a bit more margin than the 1/8" bit across the board. At the full sheet DOC, you have a little more room to get chips evacuated. We have had issues (need to fix, just low priority) with our air blast/cooling setup (FogBuster), where every now and then the magnetic mount vibrates loose, or we snag a hose, etc. All fixable stuff, but the margin is the difference between failure in 30 seconds or failure in 5 seconds. Same thing with if we are slightly off with a hold down screw and clip the edge of one, or any number of other mistakes, where the 3/16 bit has survived a surprising number of times.
I probably should look into running a smaller bit again and dialing in the process/failure modes, which would bring the spindle speed up among other benefits, and I bought a few 4mm bits to play around with as a step between the 1/8 and 3/16 options.
Out of curiosity, if you are running max speed, what are your speeds/feeds/bits/cooling setups in aluminum?