Endmill Damage-What would cause this?

I was cutting 1/2" thick oak for the first time yesterday with the f/s from carbide create and the 205 1/4’ endmil. Cutting seemed to be fine. Today i was changing endmills to start a new project and noticed some nasty looking scratches and scuffs on the endmill. I did my best to photograph it as best i could. Any idea what would have happend here?

The second picture looks like scratches. I would start with cleaning the bit. Many times residue from the sap in the wood will get burned into the bit making it appear as scratches. I used to use Rockler Bit and Blade cleaner but recently got the CMT Bit and Blade Cleaner. The Rockler was mixed with water and you immersed the blade or bit in the mixture and let it sit and then I used a stiff nylon brush to clean it. The CMT you just spray on and let it sit and I still use the stiff nylon brush to clean. After cleaning I spray a rust preventative to make sure I dont get surface rust start to form on blades/bits that I put into storage.

An alternative is using lye to clean bits that have aluminum residue but be careful as the lye is caustic and has fumes.


As @gdon_2003 said, clean it first. I have a ziploc bag with some WD40 in it. Collets, bits in it for a while. Clean rag to dry or remove oily residue and blast air if you have it. The scratches may be from dirt that has grown into the tree. I have found some pea-sized pockets of dirt.

Did the cutting edge get damaged?

Good luck

As @Zman said WD 40 works but if you clean collets you need to degrease them before using them. A shot of brake cleaner or other degreaser should be used on collets. You want collets clean and free of oil used on any router. WD 40 has a lot of uses but is not a good lubricant. It is oily but after a few weeks it dries up and becomes gummy.

I agree with all of the above but

What brand bit is this?

I ask because the only bit I see on the Carbide website is this one…

Essentials #205E .25" Flat Cutter and it does not look like the one you have in the picture. I dont have a 205 bit to compare but to me it does not look the same…I may be wrong!

What was your depth of cut?

I kind of looks like a single flute bit cause it is showing a single cutting surface.

If that is the case with or without any of the causes mentioned from the other guys a single flute will build more heat and the addition of dirt, sap or even tight grain it could cause that damage.

I use two flute bits to have two cutting surfaces and it is better for chip removal.

I would look at a two flute bit and see what that does for your problem.


Thanks for the cleaning advice. it looks and feels like scratches to me but i’m far from an expert. I’ll try a little wd40 first because i have it on hand and will look and something stronger if i don’t have any luck. The cutting edge doesn’t look damaged to me but i find it really hard to tell to be honest.

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The endmill is actually a the 205 that C3D sells, sorry for my crummy photography skills :slight_smile: My DOC was .04 at 60ipm at 18000 ( 3 on router dial) . Whenever i’m cutting a new material for the first time, i usually stick with the CC defaults. The cutting sounded ok but it did make some higher pitched sounds that were new to me. I recall reading that oak can sound really loud when cutting so i didn’t think much of it.

Any bit can be determined to be sharp or dull by running your finger across the cutting edge. Just dont cut your finger. Bits that feel share are sharp. If it feels dull then it is dull. Our fingers are very precise measurement instruments. A dirty bit can feel dull do do not test the bit until it is clean. Obvious damage to the cutting edge is a throw away. You can recycle carbide bits but finding someone to take it and be economical can be hard. The flutes on the C3D bits are not cutting the material only rubbing against it. The flutes are mainly used to flow chips away from the cutting zone. So even if the bits are scratched if they perform well i would set them aside and use them as a last resort. I always keep spares because you never know when an accident will happen and a bit gets broke or damaged.

There may have been a foreign object embedded in the wood.

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