What causes this?

Ok. Basically title tells the tale. What causes this. 1flute downcut carbide 1/8 bit. 1300mm/min 2mm doc. It has recently started doing this. Any clues?

Looks like a lot going on there, Are you asking about the tearout on the cut edges, or the unevenness of the pocket?

What RPM are you running at?

Uneven pocket? I was talking the tearout. I am running dewalt 611. On setting just under 5.

That’s gotta be an up cut bit. Else your bit is toast. Have you used that EXACT wood before? I use dumpster wood and I found this strange plywood that gave horrible results… I think was designed for underlayment.

5 is way to fast for most bits.

What kind of wood is that? I rarely go over 3 for the speed of my dewalt. The bit is not cutting well at all.

Try a downcut bit.

This is a down cut bit. I will slow it down and try again.

Yes I have used this wood before. It is 3/4 oak plywood.

The machine also apparently did not cut the shapes out correctly. Or it missed some parts.

I have to increase the stepover on some of my endmills to get smoother results.

It looks like the high RPM may have been really heating up the bit, that can cause it to dull quickly.

Sad face. That’s what I was fearing. I was following gwizard. Guess I didn’t set it up right. I’ll go back to “3” and recut. After buying new bit.

Start with 1 and move up only if necessary. If you have a feed rate of less than 90 inches per minute with a .125 bit in plywood 1 is already faster than recommended for good chip loads

So. New bit. Slower spindle speed,1.75-2ish. And wow. Works just like new… No pun intended. Lol

Perfect cuts. Perfect shapes. Only issue… I didn’t take into account shorter bit. Left dust shoe the length it was. And… Eaten shoe. Lol oh well.


Allen - what is your perspective on depth of cut: I can only find 1/2" DOC 1/8 down spiral (right hand) bits, but I often need to cut 3/4" material. If my shaft is 1/8" and the rated DOC is 1/2" do you think I could cut to 3/4" of an inch using multiple passes? Shaft would be the same diameter as the cut. It is down cut so it would not interfere with chip evacuation. I was going to try it but thought you might have input.

That depth is no problem at all I cut .75 inch material all the time like that. Just be sure you removing the chips while you cut. It is also better to make your profile cuts at least 1.5 times as wide as your cutter diameter.

1 Like