Amana specs for their 1/4" compression bit in Baltic Birch has the following speeds and feeds for their 2-flute:
What confuses me is that for higher DOC they recommend slower feed rates: 2D = 25% reduction, 3D = 50% reduction. These reductions would give a chipload around 0.002 (+/- .0002), which in my research says is way too small and I’d think the bit would overheat really fast in those conditions. What gives?
Amana’s specs are just guidelines. They are generally more applicable to much larger machines. I don’t know what machine you have but I would never run a desktop machine like a shapeoko at the same speeds listed in Amana’s specs without testing and working up to them.
Also, a 0.002" chipload is perfectly reasonable in most wood. It will wear the tool faster than a larger chipload because you are taking more cuts to remove the same material but it should work fine. You are going to have a real chip clearing problem on a 1/4" endmill at 3/4" deep though. Recutting chips will cause heat issues. All this is really dependent on material, cut path type and geometry.
EDIT: I just did the math and I run many tools (1/16" to 5/8" diameters) down in the 0.001" to 0.003" chipload range when I am going for surface finish on my 5x10 Avid machine. It works great and I run tools for hours this way. I think a bigger deal for preventing heat and premature wear is dust collection and chip clearing.
I’ve never had much luck with their speed charts, find them pretty useless. I’ve had better luck using settings from other companies with Amana bits.
I could probably run close their speeds now with my 220v 3hp spindle. I’ve ran faster, slower, everything under the sun. What i’ve learned, which doesn’t help you much, is that every machine has it’s own speeds and feed that work, with materials and your projects. So even what you find on here from others, might now work very well for you at all.
You really just have to sit down and do some testing with the materials you use and the programs you run and figure out what you can do.
I guess I’m always searching for better speeds and feeds and ways to prove that a larger spindle would solve some of my problems. I run my SO5 pro @ 18k, ~140 IPM, 0.375" DOC, with a compression bit with a Makita router and I have some heat issues every now and again, but I hate having to do 3 passes instead of 2. There’s been threads here of people reaching over 200 IPM with a 2.2kW spindle which would be a dream if I could cut that if my expensive bits last longer.
I run a small business so a larger, more rigid machine is a few years away yet. Trying to get all that I can out of this one while it’s still meeting my needs.
I can’t run 200 with what I do, never been able to get close to that, I think the spindle can do it but the machine can’t it’s not rigid enough.
I will replace my Pro5 some day with something more rigid if I figure out what that is. I’d like closed loop steppers so it would know when it has slipped and stopped, that’s the biggest issue I see with the Shapeoko, it slips and keeps going and then completely ruins whatever you were working on, it’s just stupid.
Hmmm… this is a real can of worms time. Finding the ideal feed rate and and linear traversal speed are not quite the absolute values that they may appear to be on first flush. There are many formulaic F & S constructions available from many reliable sources but using the numbers requires some tempering.
Citing DOC without discussing the material to be cut, its thickness and character when heated, the type of tooling and tool engagement, the linear feed rate, the milling direction (climb or conventional) the tool size, cutter type, coating and deflection characteristics, the material removal rate required and the desirable surface finish characteristics (to say nothing of chip load and chip thinning) is to over-simplify the factors that should ideally be known, understood and taken into consideration.
In a general sense, you are likely to find that the tooling feed and speed numbers from cutter manufacturers do not apply to small desktop/benchtop/hobbyist machines. The derived numbers will most probably have come from seeing how the cutters perform in industrial strength CNC machines which are running industrial strength jobs.
Where do you start, given the foregoing? Look at the material you want to cut and try to assess how it will affect the total cutting performance. Will it require a specialised cutter such as a downcut or a single flute cutter for a specific performance? What will the effect be of any chips that cannot be adequately cleared? Can the chips be used to reduce heat in the workpiece and the cutter? Does the cutter benefit from one of any number of different coatings? What is the tool engagement percentage for the intended toolpath? Is the cutter likely to be deflected by too fast a linear speed? Can the cuts be managed better by changing the toolpaths, tool engagement, cut order or direction?
Initially, you have little option but to ask the forum membership and discuss the materials, toolpaths and the tooling you wish to use. Test as many different tools and approaches to machining the materials you want to work with. Your machine will tell you when it is straining to cut something. You will hear a change in cutting note that suggests that some values need to change. Carbide Motion will allow you to adjust the linear speed of the cut during the cutting process. Any F & S rates you read about will just be a starting point. Often they are conservative and can be adjusted but take it slowly. Adjust one value in your processes at a time because if you adjust several things at once and things improve, you will find it difficult to know what caused the improvement.
Good luck!
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