Carve time vs. carve depth

Hello all,

I’m trying to wrap my head around this and can’t figure out why … I have a sign I am carving, all text, with a 60-degree bit at .118" depth, depth/pass at .006 and the carve time was 1hr. I was concerned I was losing some definition on the letters so ran a test at .05 carve depth and was happy with the look. When I go to run the carve, with a bit depth half the first carve, my carve time jumps to 2hr 15min!

How can the carve time increase when you reduce the carve depth? Depth/pass, feed rate all stay the same. Only thing changed was carve depth and the time changes dramatically.

I notice this often on carves when I am adjusting the carve depth. Sometimes it’s the opposite and I will increase the carve depth and the carve time gets shorter!

I do take in to consideration the depth/pass combined with the carve depth in figuring how many passes, but I’m not talking about adding passes and more carve time. It’s the opposite!

Can anyone explain?

It might be because it takes the Vbit so long to make a flat bottom. When you make the depth more shallow and only use the Vbit the bottom has a larger flat area which take the Vbit longer… just a guess.


Jason is correct.
Look at the profile a V bit carves. If you are not letting it cut full depth it increases the time.
Also why only 0.06 depth per pass?
That is extremely conservative.

Thanks Jason. That makes perfect sense!

Hi Mark,

I’m carving on Red Oak and I’ve found that if I go any deeper, I don’t get as clean of surface/face edges on the text aspects of the carve. I could spend time cleaning up with a Dremel post-carve, but then the edges aren’t as sharp. Since these are filled with resin, that crisp edge is really important.

Red Oak is problematic with cnc carving.
I have found that if you follow up your V carve with a second pass at full depth can help greatly.

Hi Mark,

For the work I’m doing with the Red Oak, it is a shallow carve in the end of only 1/8” total. I found that several passes with the v-bit works well and I get very clean edges.

I am curious what you mean that Red Oak is problematic. Maybe I’m dealing with something I wasn’t aware of! The only woods I really carve on it is red oak, poplar, heart pine and basswood. Occasional thin sheets of walnut and zebra wood.

My reference to problematic is that it does not cut clean and leaves those rough edges.
You mention you have carved walnut. Did you not notice better results in the walnut?

The red oak I carve is 3/4” think and the walnut is 1/8” for inlay, so not really a good comparison. I guess I’ve been lucky with the red oak as i haven’t had the rough edges. Then again, I resin fill and that very well could be hiding those imperfections, but they have been clean for me.