CNC Basics Tutorial PDF Guide

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  Key takeaways
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  Reading the drawing before any CNC basics tutorial PDF guide step
• 3
  Choosing tooling and workholding for a first cut
• 4
  Setting speeds, feeds, and depth of cut
• 5
  Holding tolerance and checking the result
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  Mistakes that scrap a first part
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  Five steps to cut a first part
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  Setup choices by part type

Every first part starts with the drawing, not the machine. Pull out the datum, the tightest tolerance, and the surface finish callout before you open CAM. A part with a ±0.005 mm bore and Ra 0.8 μm on one face is a different job from a bracket held to ±0.1 mm.

Note which features must be cut in one setup. Datum faces should be cut first so later operations reference something real. If two faces carry a tight relationship, they belong in the same setup or on the same fixture.

Write down the material grade. 6061-T6, 304 stainless, and Ti-6Al-4V behave very differently at the spindle. The grade also tells you whether you need coolant, air blast, or a coated carbide insert.

Finally, check the stock size against the machine travel. Our 3-axis machines cover 500 × 500 × 450 mm and 500 × 310 × 200 mm envelopes. Larger parts move to a 4,000 mm machine, which changes the fixture plan.

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  Datum firstCut the reference face before anything else.
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  Tightest toleranceFind it and plan the measurement around it.
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  One-setup featuresGroup features that must share a setup.
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  Stock vs. travelConfirm the part fits the machine you booked.

Tool choice follows the smallest internal radius and the deepest pocket. A 6 mm end mill reaches a 3 mm corner radius, so a pocket drawn with a 2 mm radius needs a 4 mm cutter or a smaller tool with a longer reach. Long tools deflect, so keep flute length close to the depth of cut.

For aluminium, three-flute carbide end mills clear chips well and allow fast feed. Stainless and titanium want more flutes and a tougher coating, with reduced surface speed to control heat. PEEK and other plastics cut clean with sharp, polished flutes and high spindle speed.

Workholding is where most first parts fail. A vise is fine for a rectangular block; a thin plate needs support under the whole face or it will chatter. Soft jaws machined to the part profile hold better than a standard vise on round or irregular work.

Plan the zero point before clamping. Set X and Y on a finished edge or a ground pin, and touch off Z on the top of the stock. Record the offsets in the program so a re-run does not depend on memory.

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  Match radius to toolCorner radius drives the smallest cutter.
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  Flutes by materialThree flutes for aluminium, more for steel.
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  Support thin platesUnsupported plate equals chatter and poor finish.

Surface speed sets the starting spindle rpm. For 6061 aluminium with a carbide tool, 300–500 m/min is a safe range. Stainless 304 drops to 80–120 m/min, and Ti-6Al-4V sits near 40–60 m/min. Convert surface speed to rpm using the cutter diameter before you touch the control.

Chip load is the other half. A 6 mm three-flute cutter in aluminium runs well at 0.03–0.05 mm per tooth. Feed rate equals rpm × flutes × chip load. If the chips come off as dust or fine powder, the feed is too low and the tool is rubbing.

Depth of cut depends on rigidity. A rigid setup in aluminium can take 1–2 mm axial depth at a 50% stepover. A long tool in stainless should start at 0.2–0.4 mm and build up only if the machine runs quiet.

Coolant is a decision, not a default. Flood coolant controls heat in steel and stainless. Aluminium often cuts cleaner with air blast or a mist because chips clear faster and do not pack the flutes.

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  Chips tell the storyPowder means feed is too low.
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  Start conservativeIncrease feed before you increase depth.
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  Match coolant to materialFlood for steel, air or mist for aluminium.

Tolerance is a process, not a number you hope for. A ±0.005 mm feature needs a climate-controlled room, a sharp tool, and a rigid setup. Temperature swings of 5 °C can move a 200 mm aluminium part by more than 0.01 mm, so warm up the machine before the finish pass.

Measure the feature that matters, not the one that is easy. A bore held to ±0.005 mm should be checked with a bore gauge or CMM, not calipers. Record the reading and the room temperature together so the number means something later.

First-article inspection catches setup errors before the batch runs. We inspect raw material on arrival, monitor in process, and check 100% of parts before shipment, with reports available on request. That discipline is what keeps scrapped batches rare.

If a dimension drifts, stop and find the cause. Tool wear, thermal growth, and loose workholding each show a different pattern. Chasing the offset without fixing the cause just moves the error somewhere else.

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  Warm up firstLet the spindle and casting settle before finishing.
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  Right tool for the checkBore gauge or CMM for tight bores.
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  Fix the causeDo not chase offsets without a reason.

The most common error is trusting the CAM simulation instead of the machine. Simulation ignores tool deflection, chip packing, and fixture flex. A quick air run with the tool offset up is cheap insurance.

Second is clamping on a finished face. Vise jaws leave marks and can distort a thin wall. Clamp on stock that will be removed, and leave a tab if the part has thin sections.

Third is a finish pass that is too slow. Crawling the tool across the surface rubs instead of cutting, which raises the finish value and dulls the edge. Keep the feed up and the depth shallow.

Fourth is ignoring the material condition. Stress-relieved 7075 behaves differently from a cold-rolled bar that will move after machining. Ask for the temper and the stress state before you plan the finish passes.

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  Air run firstCatch offset errors before the cutter touches stock.
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  Clamp on wasteNever clamp a finished surface.
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  Keep feed upA slow finish pass rubs, it does not cut.