You're at the vise with a 6061-T6 plate and a 5052-H32 blank, both needing the same Kennametal B411 end mill. Same tool, same diameter, same four flutes—so you might expect one number to cover both. It doesn't. The 6061 is a structural aerospace alloy for CNC; the 5052 is a marine forming alloy that resists corrosion but cuts differently. Add temper—T6 on one, H32 on the other—and the same cutter asks two different questions. Decide which blank you're cutting first, because the starting speed for one is not the starting point for the other.
The same B411, two different alloys
Lay the two blanks side by side and they look like the same silver-gray metal. Touch them and the 6061-T6 plate feels stiffer under your thumb; the 5052 blank has a bit more give, the kind of material that forms and springs back. That difference is not cosmetic. When the B411 flute meets the work, the softer, gummier alloy wants to smear; the structural grade wants to shear clean. You're roughing a 20 mm deep slot into each, with the same holder, same stickout, same coolant line. Both will cut, but with different chip loads, different heat generation, and different demands on the machine. So when someone hands you a single 'aluminum' speed and feed, ask which alloy, which temper, and which machine they used.
The 2026 alloy comparison guide files 5052 under Marine · Forming · Enclosures, while 6061 sits under Structural · CNC · Aerospace. The aluminum sheet buying guide adds: 5052 is chosen for corrosion resistance and formability, 6061 for strength and machinability. For the B411 that means 5052 will shear a continuous, easy chip in the right temper, but the same cutter on 6061-T6 cuts a harder matrix that holds an edge better and demands more attention to chip evacuation. 'Excellent machinability' is not a permission slip to ignore chip load; it is a promise that the alloy will respond predictably if you respect the conditions. Those differences drive corner engagement and built-up edge behavior between the two blanks.
Here's the trap: the web is full of 'B411 6061 speeds and feeds' tables that look authoritative and contradict each other. One says 8000 rpm, another 12,000; one says feed 1500 mm/min, another 900. The people who posted them were cutting different diameters, depths, machine conditions, and sometimes a different material they called 'aluminum' loosely. The lesson is not that those numbers are wrong; it's that a number without its conditions is a souvenir, not a spec. The only way to make a chart work is to understand what makes a starting point valid: alloy, temper, tool geometry, machine rigidity. Once you can derive the answer from those, you stop memorizing and start adjusting. Every table is a snapshot of someone else's setup.
Before you load 6061-T6, know your temper
The temper designation after the alloy number is not paperwork. T6 means the material was solution heat-treated and artificially aged; H32 means it was strain-hardened and stabilized. The temper guide warns that the wrong temper can cause cracking during bending, excessive springback, poor finish, or unnecessary difficulty during fabrication. On the machine, that translates directly to cutting behavior: T6 aluminum is harder, so it shears with a more brittle, segmented chip; a soft O-temper blank is gummy, so the edge pushes and smears instead of cutting clean. The same alloy in two tempers can have visibly different burr formation and built-up edge tendencies. If you see a speed-and-feed table that lists only '6061' without a temper, walk away—the number is telling you half the story. You're not cutting '6061'; you're cutting a specific version of it.
Machinability ratings exist for a reason, and the alloy selection guide is blunt about them. Rows for 1100, 2024, and 3003 show the same alloy easy to form in O turning into a different cutting proposition in H18 or T6. 2024 is the clearest example: poor in O, good after heat-treating to T6. The guide's message is that machinability is not a fixed property of the alloy; it is a property of the alloy plus its thermal and mechanical history. For the B411 that means you should treat a 6061-T6 blank as a different material than a 6061-O blank, even though the name on the tag is identical. Soft tempers produce long, stringy chips that load a flute; hard tempers produce shorter, cleaner chips and let you push feed.
Here is the practical payoff. Because 6061-T6 is the heat-treated, strong structural alloy with excellent machinability, it is the version shops order for CNC work. O-temper 6061 fights back with long chips and built-up edge. So the temper shifts your starting parameters: on T6 you can enter at a higher surface speed and a slightly higher chip load, because the chip is more likely to separate cleanly; on O-temper you drop back, lower the feed, and watch the edge. The same reasoning the alloy guides apply to forming applies to machining: temper controls how the material yields, and the cutter is a controlled way of making it yield. Every time you see a forum post that says 'I run 6061 at 10,000 rpm,' the first question is not whether 10,000 is right, but which temper the poster was cutting.
Why spindle speed isn't the only answer: the speed and feed causal chain
Start with the two formulas that keep every speed and feed table honest. Spindle speed in rpm comes from the surface speed you want at the cutting edge divided by the tool circumference: rpm = (surface speed × 1000) / (π × diameter). Feed rate comes from the chip load each tooth carries, multiplied by the number of flutes and the rpm: feed = chip load per tooth × flutes × rpm. When you search for 'B411 6061 speeds and feeds,' you are looking for someone else's output of these formulas, but their inputs—diameter, flutes, depth, machine stiffness—are not printed on the page. A generic table fails because it hides the variables. The honest way to use it is to take the surface speed range, run it through your own diameter and flute count, and set the chip load from the material and operation, not from a screenshot.
Now the physics that makes aluminum different from steel. The technical manual on aluminum coil states it directly: aluminum is about one third the density of steel, and it conducts heat and electricity well—about 62% of copper's conductivity by cross-sectional area, but 204% by weight. That combination means the heat generated at the cutting edge is pulled away quickly, and the workpiece is light relative to its volume. So aluminum can take much higher surface speeds than steel before the tool overheats. But there is a catch: the same heat that dissipates quickly can, if the chips are not clearing, weld itself to the edge. The very property that lets you run fast—thermal conductivity—requires that the chip actually leaves the flutes. If it doesn't, you get a built-up edge and a torn surface finish. 6061's softness does not mean slow speeds; it means you manage the chip.
The brand context matters less for the formula than for the tool's consistency. Kennametal is an American manufacturer of high-performance cutting tools for aerospace, defense, transportation, and oil and gas drilling. When you buy a B411 from Kennametal, you're buying a tool designed for exactly these materials, and its geometry—helix angle, flute polish, edge prep—is already tuned for aluminum. That means your job is not to compensate for a bad edge, but to respect the variables the tool cannot control: tool diameter, flute count, stickout, and machine rigidity. A 10 mm, 4-flute B411 in a rigid holder has a wider safe window than the same cutter sticking out 60 mm from a collet in a light-duty mill. Every variable multiplies the stress on the edge and changes the first safe feed. The tool can handle high surface speeds, but the setup has to be capable of delivering them.
First starting parameters for the B411 on 6061
For a 10 mm, 4-flute B411 in 6061-T6 on a rigid CNC mill, a sane first set is a surface speed of 350 to 500 meters per minute, which works out to roughly 11,000 to 16,000 rpm for a 10 mm cutter, and a chip load of 0.03 to 0.06 mm per tooth, which puts feed around 1,300 to 3,800 mm per minute depending on your rpm. These are starting points—industry-sane numbers for a carbide end mill in a rigid setup with good coolant or air blast. If your workpiece is large or the slot is deep, enter at the bottom of the ranges; for a 20 mm deep slot, rough in steps. If you switch to a 6 mm B411, scale the rpm up inversely and keep the chip load per tooth about the same. The first cut should be a probe, not a production pass.
Set the parameters, then watch what matters: the chip. On aluminum, the chip should come off as a clean, bright curl or a series of small sixes—not a powdery dust, not a long stringy weld, and not a silver smear that sticks to the flute. The same thermal conductivity that lets aluminum run fast (62% of copper by area, 204% by weight) only helps if the chip actually clears the flutes; a chip that stays in the cut becomes the heat source that welds onto the edge. So the moment you see a bright welded streak on the carbide, you have your signal: either the surface speed is too high for the chip load, or the chip load is too low to lift the material away. Stop the spindle, brush the flute, and change one variable—usually chip load first—before you change speed.
Long stickout is the silent killer of speed and feed tables. The formula assumes a short, rigid setup; the closer the B411 gets to a spring in a collet, the more the tool deflects, the more it rubs instead of cuts, and the sooner you will see chatter or a broken corner. Same for workholding: a thin vacuum pod or a soft-jaw fixture that moves a hair can turn a good feed into a bad finish. A long stickout changes everything; when the tool extends more than four diameters, back off both speed and feed. If the cut chatters, do not drop rpm and raise feed in the same edit; pick one, record the result, and give it two cuts to prove itself. The rule is not a pair of numbers; it is a measurement loop.
Verify, adjust, then build your own parameter table
You can see the health of the cut in three places: the chip, the sound, and the surface. Compare what you get on 6061-T6 with 5052 or 7075, and the difference shows up in chip shape and edge finish. The alloy comparison guide is honest that these grades occupy different applications—marine forming versus structural CNC—so your table gets different feeds and speeds for the same tool. A chip on T6 that comes off as a tight curl tells you the material is shearing; a long ragged ribbon tells you the edge is rubbing. Listen for a steady note; a changing pitch is the first sign of loading. Check the finish for a skid pattern; that's built-up edge dragged across the surface.
Keep a log. When you change speed, write down the rpm, the feed, the depth, the chip shape, the finish, and the sound. Then change one thing, repeat, and compare. The first cut in the log becomes your baseline, and every later decision is a measured deviation from it. Write it before you touch the control. This is how a chart becomes your chart: not by copying, but by recording the cause and effect of each variable until the causal chain is yours. It gives you data you can trust because you watched the chips yourself. Two cuts on paper are worth more than a screenshot of someone else's settings.
Your own parameter table won't come from a single perfect setting; it'll come from a tested range. When you have a baseline, a log, and a habit of changing one variable at a time, you can predict how the B411 will behave on the next 6061-T6 job before the spindle starts. That is the level where the same cutter stops being a gamble and becomes a known tool. The starting numbers from this article are just a door; what you build behind the door is your own. Nobody's chart, including the one on the tool manufacturer's site, can include your stickout and your workholding. Only you can do that.
Start conservative on chip load, let the chip form guide you, and never trust a chart that ignores temper and stickout.
