Thin strong bit for fine line cutting acrylic soft plastic?

I picked up this bit here 30423-01, and once it started cutting the bit snapped within 2 seconds. My depth per pass is .050

Is there another bit someone can recommend a thin bit for cutting fine detail ?


I’m not an authority, yet :wink:, but, 0.050" seems too deep. Let’s see what others say.

I’m no expert either but my understanding is that you can take a pass as deep as the diameter of your bit - IE: using a 0.125" bit should allow you to take a pass at a depth of 0.125" max.

Does anyone have any real world experience with this ?

Interesting, because the bit was barely in. My feed rate was 25 in/min
.125 is deeper than .050

my bit is .0625, and my depth per pass was .050

From what I’ve read, a good rule of thumb is to make your depth of pass half of the width of the bit. So, a pass for any bit of that size should be .03 or less.

1 Like

On my mill I go with 1/2 width for max depth, but I’m not a machinist and my mill doesn’t have power feed. It does weight a ton though, with no vibration. When you use the long thin bits you’ll need to use perfect feed/speed and have no vibration or flexing anywhere or you’ll snap the bit.

If you’ve got the calibrated eyeballs, you can try grinding the flutes on the end of the broken bit and re-using it. The shorter length will take more abuse. And if your line doesn’t need to be flat, I’ve had good luck using center drills (double-ended bits for starting/spotting holes on the lathe) to engrave lines on metal, they should be able to handle a light groove in plastic. If you’re going to be using the tiny bits a lot and don’t have the $$ to treat them as expendable, you might try googling around for “stubby” end-mills. I’ve grabbed a few out of old machinist chests, don’t know if anyone still sells them.

1 Like

@GamerGuy I assume you were using a 1/16" bit. In my experience 0.050" is too deep for a bit that diameter. I’d try 0.020" max depth per pass. 25in/min is a good place to start and adjust from there.


From what I remember from school when I did CNC milling this is the rule of thumb we generally followed; depth of cut = 0.5*Bit Diameter.

What about vbit 1/2" 90’,how can we calculate the pass.

V-Carving is still a bit of voodoo magic to me, so I can’t help out with that one. But I’m sure someone on the forums has a good general rule for this.

1 Like