Significant furring in my cuts

CNC Machines
1

Just wondering what I’m doing wrong or if I need a different settings to minimize the issue, but I am getting a significant amount of “fur” on the bottom of my pockets. When I have a basic pocket, at the points where the tool is overlapping a previous path, I get a small amount of fuzzy wood that is a pain to clean up. It happens all over the pocket, in some cases making it a real challenge to clean up.

I’m using the default feeds and speeds for the #201, and a variety of woods (both hard and soft) and it doesn’t seem to matter. I’ll try to get a sample cut going in a bit and post a picture, but I wanted to get this out there to start and see if anyone has any immediate suggestions.

Thanks.

2

Try a downcut tool such as the #251?

3

I use down cut bits a lot. However deep slots dont work well with down cut bits because the chips are being pushed down in the slot and have no where to go. Usually @WillAdams suggests adding geometry to a slot to give a little relief to the bit. That would mean if you want a .25" wide slot you might make the slot .27" so the bit makes two passes to get to .27" wide with a .25" bit. The down cut works very well on pockets that are bigger than the bit.

On slots an upcut bit works better because the chips are being somewhat evacuated from the slot. The down side of that is you tend to get fuzzies around the top lip of the cuts. That can be cured relatively fast with a quick light sanding. I keep a 3M sanding sponge on my machine and just hit a freshly cut project with that and if required run a RO sander over the surface.

Another method to help with the fuzzies is to mask the cut. I use adhesive shelf liner and there is Oramask. Both of these sticky masks need to be adhered well and I use a J roller to press it down after applying. The masking also helps if you are going to paint the project and keeps you from getting too much excess paint on the surface. The masks will fray along the edge so another method would be to add shellac to the surface to stiffen up the wood fibers and then apply the mask.

The reason for the fuzzies is the wood fibers are unsupported along the edges when cut. Unsupported wood fibers tend to fuzz up but a light sanding will usually fix that and if necessary a little bit of hand sanding will finish up the fuzz.

You tend to get even more fuzz along the edges when cutting cross grain. It is just the nature of a natural product like wood.

4

To be clear, the fuzzies are NOT on the edge of the cut at the surface of the wood, but on the bottom of the pocket. In the middle of a wide open space that has been pocketed out, it gets fuzzy, and they aren’t just loose. They are still somewhat attached…

---+                  +---
   |                  |
   |       @%#@       |
   +------------------+

heh sorry for the caveman graphics. I have been working all day and haven’t had time to get out and cut a test yet.

5

A downcut can still help in the bottom of pockets, however I would additionally check 2 things:

  1. Make sure you don’t have an endmill with a chipped corner.
  2. You may want to check the tram on your spindle. If the spindle is crooked, when it overlaps a previous path going in certain direction, it can dig up a little extra material causing fuzzies.
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