After two oops events, my endmill is now cutting "strings" of wood

This is weird. I had two oops events today. First, my work piece wasn’t secured well enough and the piece lifted and the endmill burned a hole all the way through. This loosened the endmill enough that it came out in the next cut. Lesson learned.

I tightened it up, but now the endmill is cutting strings as shown in this picture.

Any advice on what happened here. Is the endmill done?


What kind of wood are you cutting there? Sometimes certain species are more prone to stringiness due to their grain structure. It’s commonly suggested to take a look at end mill condition using some form of magnification so you can see if there is any damage/wear. A microscope, loupe, regular magnifying glass, or even your phone would likely suffice.

It wouldn’t hurt to clean the end mill especially if you haven’t done it after using it repeatedly. Link is for cleaning a table saw blade, but still applies - a container with some water and laundry detergent as well as a stiff plastic brush.


Agree with @RoughDraft40. The wood, I’m guessing pine, and the grain direction can cause that. If you’re up for a tool change you could use a downcut endmill there. Just make sure you’re clearing the chips because the downcut won’t do it for you.


The tool may be less that ideally sharp, but the bit of dust that is visible looks about right. I am presuming you did some cleaning before the picture? The ends of the rectangular path, being cross grain, should have made chips no matter what.

Strings like this can be a real problem, since they don’t clear well. They can tangle around the tool and interfere with proper cutting, among other things.

As said, a likely contributor is the tool path matching the grain direction. The easiest solution is modify the tool path. For a narrow slot, this isn’t always possible, but for many operations, it is.

If your CAM allows (many do, but not all), set the preferred cut direction for the operation at an angle to the feature. It doesn’t take a lot of angle. Just enough that the tool isn’t following the grain direction in a way that it can peel strings. Best is climb cutting out of the grain so the tool shears the chips off without tearing. (see the crude MSPAINT sketch)CUTTING-DIR

The climb cut side (above the tool) will be clean, there will be a rougher cut on the conventional cut side, maybe with tearout.


@Bonhoeffer, my guess is you are cutting poplar. I’ve got to watch my cuts with poplar (always using a , because those strings clog up my vacuum hose as soon as I turn around (yes, poplar has eyes!) :smiley:

I’ve tried @enl_public’s method, but the strings persisted in poplar. They were shorter. Plus, the clean up of the slot/pocket was worse. I had to come back with a finishing pass parallel to the grain to finish the slot/pocket.

It was better than getting the vacuum clogged and possibly getting some burning action in the cut.


After sorting the cut strategy, if there’s still stringiness on the surface, a marking knife, flat side down, is pretty good at cutting those off cleanly and doesn’t tend to round over the edges as easily as sanding does.


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