Yeah, that’s a chip breaker router designed for cutting FR4 (glass loaded PPO). They can work in other material but they are designed as a grinding tool. The standard design for those is a 5 flute at 0.0625". That’s part of the problem and why the tool is brown on the end. It’s burning the material.
Your hold down should be good for this type of cut.
Going to jump to runout for a second as it’s most likely related to the failure of this tool and likely why you were having issues with the standard mills.
Have to preface that with chipload though. Chipload is probably the most important factor in milling and half of what all feeds and speeds are trying to get to. The very simplified version of it is how wide a cut you are taking per flute. Or a sometimes easier way to think of it is that it’s how far “forward” the tool moves in one flute rotation. There’s a minimum needed for each tool geometry to actually cut a chip and not rub. Chipload along with the stepover and pass depth determine the cutting forces (for a given material).
Runout is basically how much the tool is “wobbling” or spinning off the central axis of the spindle. It directly effects the chipload because as the tool “wobbles” back and forth while it’s spinning it’s moving in and out of the cutting direction. What this functionally means is that for at least part of the cut you are cutting your chipload plus your runout AND your chipload minus your runout.
So let’s use an example of a 2 flute cutter going 1000mm/m at 20K RPM. That works out to a 0.025mm chipload (feed / RPM / flutes). Now let’s assume that we have 0.02mm of runout. What that would mean is that for the programed 0.025mm chipload (1000mm/m) it will actually cut 0.045mm on one flute and 0.005mm on the other (in the worst case, or for at least part of the cut). This mean that with your programed 1000mm/m cut you are effectively cutting 1800mm/m AND 200mm/m. This will be true until your runout is equal or great to your chipload * (flutes -1). After that your combined chipload will be cut on a single flute. Additional to that in a plunge you will take up to your entire runout as your chipload even if it’s greater than your combined chipload.
I think that this might be your issue. Usually most of the runout is in the collets and they are a consumable. So as they wear they get worse which starts to effect the cut. Don’t know what kind of collet you have but if you are going to be working with small tools (especially slotting with small tools) it would be worth getting a graded collet and potentially the tools required to check your runout.
One quick test you can run that doesn’t require any tools. Put a tool in the spindle/router and power it on and off. As it spins down watch the tool. If you can SEE it wobble you have at least 0.002" (0.050mm) of runout (with normal eyesight).
A tapered 0.0625" tool is a lot stronger. However, you are just putting an expensive band-aid on the problem. In addition if runout is the issue you are going to be dealing with a lot of other issues with cut quality and tool life. The taper also make the diameter increase the deeper it cuts and that will increase the cutting forces.
If you want a band-aid solution that’s cheaper you can just cut your pass depth down. It’s the cutting forces that break tooling and cutting force is more or less cubic material removed per flute (although the direction of the forces can change). So if you cut your pass depth in half you’ll functionally half your cutting forces regardless of how much of it is from runout and it’s effects.
Not really, The chip breaker routers were designed to cut through as many PCBs as possible at a time. So most of them are the same length of cut. There are lots of “standard” length tooling in normal end-mills (e.g. Stub 1.5x, Standard 2-4x, deep cutting 5+x).
Let me know if I missed something or you want more information.
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. In many parts of life, I compromise but this one i feel pretty passionate about and am willing to pay more for a tool for that privilege.