Feeds and speeds.

[Ntl]

As the title states, what type of feeds and speeds are some of you guys using? I found some chip load charts for the different types of materials with different cutter sizes. The chip loads seem really high compared to what some of the metal charts show for aluminum. So it makes me wonder if the aluminum is wrong is the wood wrong? Attached is a example of one of the charts, I've found a few and they were all similar. I'm just trying to figure out if the few charts I've found are accurate.

Here's a example of what I'm talking about including a tool Setting based on the chip load chart. I even went on the low end of the chip load.

The question for me is it seems very fast, the testing I've done have had no issues but the machine was hauling ass. I'm just wondering if the machine can handle the feed rates.

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[difalkner]

Typical cuts for me are at 18k rpm with a 3kW (4HP) water cooled spindle and probably 75% of what I cut is Walnut, Maple, and Cherry. The remaining 25% is cutting the Longworth chucks in 1/2" Baltic Birch -

- 1/32" end mill, 0.015" depth of cut, 15 ipm
- 1/16" end mill, 0.025" depth of cut, 20 ipm
- 3/32" end mill, 0.035" depth of cut, 25 ipm
- 1/8" downcut spiral, 0.100" depth of cut, 75 to 100 ipm
- 1/4" down or upcut spiral, 0.200" depth of cut, 150 to 200 ipm, usually in the middle at 175 ipm in hardwoods, 200 ipm in Baltic Birch but thinking about going to 250 ipm
- 1 1/2" flat bottom bit for surfacing the spoilboard, depth of cut as needed, anywhere from 200 ipm to 400 ipm and sometimes I'll drop the spindle speed to 15k or even 12k rpm but the last time I surfaced the spoilboard was at 18k rpm (that big cutter makes a LOT of noise at that speed )

V bits, 60° and 90°, usually about 75 ipm, it just depends on what I'm carving. If it's something big without a lot of detail I can double that speed.
Ball nose bits - 1/4", 3/8", and 1/2" are the same - it just depends on what I'm cutting

David

[wmgeorge]

I am more or less where David is and using an Air Cooled spindle rated at 3Hp. I have cut 3/4 inch MDF with a 1/2 inch bit in 2 passes and pushing pretty hard.

[ger21]

Most chip load charts give values for maximum tool life. The vast majority of hobby and DIY machines are not capable of achieving these rates. You'd really need a 10HP spindle and a machine capable of cutting at 1000+ipm to reach some of them.

[Ntl]

Thank you all for the answers it helps a lot since I'm very green when it comes to CNC machining.

Thank you especially David for the detailed answer I feel much more comfortable with my tool settings now. It's great to know that the machine can handle the speeds that you're running, I may not be able to achieve the same since you have a bigger spindle than I got. But at least I know the rack and pinion can handle it, I was a little worried since a lot of the industrial machines use ball screws.

So far I'm very impressed with the detail I'm getting from the machine with the few parts I've cut. It looks like this thing is finally dialed in and cutting great!!! Now I just need to get my Vetric files dialed along with my tool paths. At least I finally understand the relationship between rpm, feed rate, chip load and so on. When I first started I had no clue what any of it meant.

One more question, do you guys get a starting point based on chip load? Or do you go off of RPM? I've been using chip load to get my feed rate and rpm, but I'm curious if there's a better way?

Thanks again,
Dan