This has probably been answered here, but I looked, and couldn’t find an answer to my question.
I am doing my first 3D carving, and am doing the standing bear in a “bowl” that comes with the Vcarve software clipart.
I understand the concept of roughing, stepover etc. The question I have is when I do the roughing pass do I use a ball
nose bit, or a flat end mill? I am doing the relief in Red Oak, and it is approx. 4.5"tall X 2.5-3" wide. I have all the conical bits from .0625 to .250. Was planning on using the .0625 conical for the finish pass. Just need to know what tool is best for the roughing. Thanks.
The flat end mill should remove the most material the fastest, so is best suited for roughing.
I like to use a 1/4" flat 2 flute endmill for roughing. Then i use the conical endmill to finish.
I agree with Will and Steve that a flat end mill is best for roughing out. I just want to add that one of the main reasons for not using a ball nose is to preserve the sharpness of their blades for the final pass.
I would also reconsider using the smallest bit that you have. A larger ball nose, for the same step over, will give a smoother surface with a smaller scallop. As a general guide, you want to use the largest bit that will still get into the tightest corner of your design. Your 0.25 bit might do a better job than your 0.0625…
I’l -almost- agree with you here. Roughing with a ball will rapidly wear out the end of the cutter- there isn’t much of the tool that can be engaged. A flat endmill can be engaged up the sides and remove a lot more material for the same runtime. That the cuts look a little rough/stepped isn’t really an issue. You want to use the biggest end mill that takes out the majority of the rough material - that doesn’t necessarily mean it fits into the smallest corner. The finish tool must, but the rougher doesn’t (and probably shouldn’t so you can get a shorter roughing run). I rough pretty much everything with a .25" tool and it makes thing go much more rapidly.
I’ve been using a plunge type Router bit with the Makita to rough out MDF. The bit is 3/4" diameter, but I also have a 1/2" and a 1". It plows through the MDF so that roughing is quicker than a 1/4" for the same number of passes. I leave about 2-3mm for the 1/8" ball end cutter to smooth the surface with. I am creating a 6 part mold for a client. It has taken a lot of thought and training to get the machining times down to within 3-4 hour time slots. So far 2 parts have come out ok. I have a few multi-sided parts that are up next. The problem is the amount of dust that is created when turning sawdust with glue back into sawdust. I do where a mask and safety glasses, and try to be vigilant with the vacuum, but I think it is time to update the enclosure to contain the dust. (EDIT: spelling corrections, Also, if you want to use the larger diameter bits remember to slow down your feeds a bit plus watch out how fast you plunge as I have found that slower is better as there have been a few instances where there is a “bounce” that messes up the z-height, belt skips and so on, where you will need to stop everything and re-zero, ugh!)