Looks a little toasty to me? I noticed that some of my cuts have been getting a little rougher lately and took a look at the end mill, but other than needing a little extra sanding to clean up the edges it still works just fine. I just got my machine back in March, and haven’t had to replace any end mills yet, so just wanted to see what others thought? When do you guys decide to replace them? Do you run them into the dirt or replace them as soon as the cut quality begin to suffer? Some basic google searching also mentioned regrinding? Is that something that is worth doing at this level or is that geared more toward industrial machines?
When a tool no longer cuts essentially perfectly, I relegate it to roughing, when it no longer cuts well, it goes into the scrap box (if it seems possible that it could be resharpened I’ll leave it in its case, and multiples get put into a zip lock bag).
Resharpening requires a suitable stone and a fixture/jig which will allow presenting the stone at the correct angle — usually the setup time requires more endmills than a hobbyist is likely to accumulate in a reasonable period of time — if someone could come up with an economical approach to resharpening tools it’d be great, but the logistics of it make that unlikely for hobbyists.
If a flat endmill like the 201 still has sharp corners (compare it to a fresh one) but looks discolored, there’s a good chance that you can extract a bit more use out of it by cleaning it. Saw blade cleaner or something like Simple Green + a stiff synthetic brush can help remove carbon and tree-gunk and restore some degree of cutting performance.
Unless you’re doing metal-working, you will usually be able to see a degradation in your cut quality and take appropriate action before anything catastrophic happens.
Start with periodic cleaning of bits. The residue left by carving wood and other materials can make your tool appear dull when it is not. After cleaning simply feel the cutting edge. If it still feels sharp it is and if it feels dull it is dull. It takes a long long time to wear out a carbide bit. It is possible when cutting certain materials but just cutting wood the bit gets dirty more than it wears out. For those cutting alum then just lye in water will take the alum residue off your tools. As @wmoy suggested commercial cleaners work wonders on router bits. If they look dark it is likely just residue from whatever you are cutting. High Speed Steel can get blue from over heating but carbide would have to get very very hot before it would turn blue and lose temper. To get a carbide bit that hot you would likely set things on fire.
So give your bits a good cleaning and you might not have to replace them for a long time.
Along with cleaning your bits you should also be cleaning you collet and collet nut and the inside of your router/spindle shaft. Dirty collets and nuts can cause your bits to slip and cause issues with your carving. For collets/nuts/router shafts you can use mineral sprits, acetone, acholol but my favorite is brake cleaner. Brake cleaner has solvents to melt away residue and it dries fast. For cleaning the inside of our router/spindle shaft use a qtip sprayed with your solvent of choice and let the solvent dry before reassembling your router/spindle collet.
