I’m going to be engraving some letters with a V bit in probably oak. The letters will be a fancy script font about 1 inch high. I’m using mpcnc, dewalt 660, and estlcam.
The steeper bit (the 45 degree one) will cut deeper for the same width, so it might take a little longer, especially if you have very wide lettering. But it has a big advantage. Any error in Z height will end up being a smaller width error. It’s much more forgiving. If you have a slight difference between the Z at one end of the board from the other (due to material thickness, table not being flat, or sag in the gantry), the bit will cut deeper, making the tool path wider. If it’s a sharp bit, the width error isn’t as wide.
If you can get away with it, don’t set the max depth. Let the tool go all the way to the bottom creating a sharp valley in the middle. If you have a really wide letter, you can’t do that, but if it’s scripty, and only 1" tall, you’ll probably be able to get away with it. Then you won’t need to worry about stepover, because it will not have a flat bottom. If you need a flat bottom (in some places) do a very small step over, since the pointy bit is very small at the end. Like 5%.
I would do some test cuts, cutting something like an “A”. Start with a full depth, and slower feedrates that you would for a flat bit. It will depend a lot on how deep you’ll actually end up going. I’ve only done a few carving projects, but they didn’t take long and hardwood is expensive, so I just went ahead and picked some very conservative settings.
I read that engraving can run faster than normal cutting? Someone posted 25mm/s = 60ipm on the facebook group, I was thinking of trying at 50ipm?
Good point with the depth. Unfortunately I do have to limit the depth because I’ll be pocketing out the bottom side to mount some electronic touch sensors. But looking at the preview with and without a max depth it doesn’t seem to make a difference this time. I also just discovered estlcam’s option for using a flat bottomed bit first and finishing with the vbit, also didn’t seem to make a difference in the previews.
It won’t unless you’ve got fat letters and a smaller max depth. If you put the max depth at like 0.01mm, you should see what it does.
I’ve been pretty happy with 12mm/s in Estlcam. I found it quite challenging to understand how the 1/8" 45 degree vbit went into the material. Getting the right font and then getting the carving to do what I wanted was quite the thing. I started a file with different fonts and different letter shapes to see how the vbit carved it up in Estcam. I hope to get back to that file and post results
The depth thing is a challenge. Depending on the font and the letter, I got good results or bad. I generally put in 4mm. But I don’t make my letters bigger than 1.25".
Then there are sometimes that the letter doesn’t want to get a good single path. For example, the letter A has the counter (triangle piece) in it. The line under it or the inset path of the letter R that curves in doesn’t get cut.
I don’t do a stepover for this size of letters. It gets a pretty crisp carve with one swipe. The vcarving is generally done with one path per section rather than multiples. That’s why different sizes of bits are most appropriate for different sized letters.
I know I am not helping you much. Test in foam first until you have the carve you want. The oak will be no big deal. The vbits I got from Ryan are holding up great.