Just getting started with some 3-D carvings. I picked out one Michael Tyler’s mantel clocks. I think it’s about 9x12 in size. Nice piece and not too complicated to put together. I knew it was going to take a while to carve, but wasn’t quite prepared for 12 hours or so of machining. Wow.
So, I’d like to do some additional carvings in the future, but wanted to ask some questions about workflow, bits, feed rates, plunge rates, spindle speeds, etc. I’m carving red oak.
I am currently using an Amana 1/4" two flute bit for the roughing cuts. I found that the plunging is what really takes the toll on the bit, whereas just moving in a straight line is not too difficult. I’ve slowed my plunge rate down to about 25, and that seems to be comfortable. I use some charts from Vortex tools, and came up with a speed of 200 ipm, at about 12,000 RPM. That seemed a bit too fast, so I dropped that down to 180 ipm. I found I’m able to speed that up to almost 200% 360ipm, on some of the final passes, but the flip-side is I need to drop it down to about 60% to 70 or so ipm with a really deep plunge cuts. This pretty much means babysitting the machine and adjusting on the fly. There does not seem to be any way when adjusting a tool paths to be quite so selective. I’m currently using Vectric Aspire.
While the rough-cut is fairly fast compared to the finishing cuts, it still about an hour and a half. Once I switch over to the ball nose for the finishing cuts, oh boy do things ever slow down. I’ve been running a tapered ballnose (1/8", 5.4 degree specta coated) at about 180 ipm. It has a suggested plunge rate of around 45, but again to me this seems to kill bits. I’ve slowed that down to 25. Mostly I’m just going by sound. The suggested overlap is around 8 to 10%. I have no idea if these numbers are in line with what other people are using, so I’m seeking guidance. I’d love to be able to speed the process up some. Michael Tyler recommends a 1/16" bit, and no question the results are superior to the 1/8", but it adds an extra three or four hours to the already long time. How are people dealing with these long times? I’m afraid to leave the machine unattended.
Today in an hour and a half one of the bolts on my spindle came loose! Fortunately the bottom one was still tight so no damage was done, but the results could have easily been disastrous. I’m amazed how the vibration of the machine loosens up bolts. I’m starting to go around and use Loctite where I can, but can’t do that on the spindle, as I adjust it frequently.
The other thing I had never even considered was the heat generated by the vacuum cleaner. I’m using a Fein, which has incredible suction, but over the course of several hours in a small room it can raise the heat levels considerably. I’m not so sure that running a vacuum cleaner that long is good for it either. I think that machine is something like 12 A, so definitely sucks up the energy. Has anyone had much luck with a smaller vac? I can say for my roughing cuts I really need the extra suction, but for the finishing cuts it’s mostly dust, and not chips, and I would think a smaller vacuum would work. Again, not something I ever considered, but it’s now an issue.
So, looking for some feedback as to bits to use, feed rates, plunge rates, rpm’s etc. and general suggestions on workflow to speed up the process. BTW, I’m using my tapered ball nose bits at 18,000. Tools today has some pdf’s you can download for the various bits and that’s kind of what I’ve been going by as a starting point. I can say that the suggested speed rate was something like 45 ipm on the ball nose, and that’s crazy to me. I can easily run that at about 180 ipm with no problem. I’m guessing it could even go faster but it’s a $65 bit, and don’t want to snap it.
Many thanks for helping out a newbie!