Sectioning Techniques

Introduction

Sectioning is the first step in metallographic sample preparation. The goal is straightforward: cut a representative sample from the bulk workpiece with as little damage as possible, so the grinding and polishing that follow can remove any cut-induced damage and reveal the true microstructure.

PACE MAXCUT abrasive cut-off blades and PICO-series precision wafer blades cover the full range of metallographic sectioning needs.

Every sectioning operation can be judged by the same set of effects.

Two methods cover almost all metallographic sectioning: abrasive sectioning for routine metal samples, and precision wafer cutting for delicate, brittle, electronic, or thin-section work. The two methods use different blades, different machines, and different parameter ranges. The choice between them shapes everything downstream.

Sample Planning

Before any blade touches the part, two decisions matter: where to cut and how to orient the cut. Both determine whether your final polished surface answers the question you are trying to answer.

Locate the area of interest

The cut should pass close to the feature you want to examine: a weld fusion zone, a fracture surface, a case-hardened layer, a coating interface, a specific grain orientation. For directional features like welds, columnar castings, or fiber-reinforced composites, the cut plane and the feature orientation determine what you will and will not see at the microscope.

Allow for the damage zone

Sectioning always introduces some surface and subsurface damage. Cut at least 1 to 2 mm away from your true area of interest so that grinding can remove the damaged layer and you reach a clean microstructure. For soft, ductile metals (aluminum, copper, lead), allow 2 to 3 mm; deformation runs deeper in soft materials. See the Grinding Techniques guide for how the damage layer is removed in the next step.

Keep coatings in compression

When sectioning a coated or plated sample, orient the cut so the blade enters the coating and exits through the base material. This keeps the coating in compression during the cut and prevents it from spalling or chipping off at the substrate interface. The same orientation rule applies whether you are using an abrasive blade or a precision wafer blade.

Choosing Your Method

Abrasive sectioning and precision wafer cutting are not interchangeable. Pick the one that matches your sample size, material, and damage tolerance.

The rest of this guide is split into two self-contained tracks. Read Abrasive Sectioning if you are cutting routine metal samples. Read Precision Wafer Cutting if you are cutting brittle, delicate, or precision-located samples. Universal Best Practices and Troubleshooting apply to both.

Abrasive Sectioning

Abrasive sectioning uses a rotating, bonded abrasive wheel to cut through metals, plastics, and many composites. It is the workhorse of metallographic sample prep: fast, versatile, inexpensive per cut, and capable of handling a wide range of materials from soft aluminum to case-hardened tool steel.

How abrasive cutting works

An abrasive blade is built from abrasive particles held together by a bonding matrix. As the wheel rotates, particles at the cutting edge fracture or wear, exposing fresh abrasive while removing material from the workpiece. The right combination of abrasive type and bond hardness matches the breakdown rate of the bond to the wear rate of the abrasive, so the blade keeps presenting sharp particles to the cut.

Abrasive types

• Alumina (aluminum oxide): moderately hard and relatively tough. The default choice for ferrous metals.
• Silicon carbide: very hard, but fractures and cleaves easily, which makes it self-sharpening. Better suited to non-ferrous metals like aluminum, titanium, and zirconium alloys.

Bond types: resin vs. resin-rubber

The bond matrix has a bigger effect on cutting behavior than most operators realize, and the trade-offs come down to smell, life, and forgiveness.

• Resin-bonded: less odor, breaks down faster (continuously renewing the cutting abrasive), produces a modestly cleaner cut, and is less likely to burn the sample. More versatile across materials.
• Resin-rubber bonded: longer service life, more aggressive cutting, but produces the familiar burnt-rubber smell and is more likely to burn the sample if parameters are wrong. Finding the right resin-rubber hardness, abrasive size, and thickness for a given material historically required experimentation, which is why resin-only formulations have steadily taken over.

PACE MAXCUT blade selection

PACE Technologies manufactures the MAXCUT line of abrasive cut-off wheels. Each series is formulated for a specific material class. Use the table below to select the correct series, then pick the size that matches your cutter's wheel capacity.

PACE MAXCUT abrasive blades. Each series is formulated for a different material class.

Picking blade diameter: use the smallest wheel that can still accommodate your sample. Larger wheels cut larger pieces but generate more heat and waste more material as kerf. The size suffix in the SKU (250, 300, 350, 400) is the wheel diameter in millimeters.

For the full SKU list, pricing, and stock, visit the Abrasive Cutting Consumables page.

Abrasive cutting parameters

Most metallographic abrasive cutters run at a fixed wheel speed. Typical speeds are 2,800 to 3,800 RPM for 10–14″ wheels. Your primary adjustable variables are feed rate, force, and coolant flow.

Feed rate and force

Apply steady, moderate force. Light pulsing motion often produces the cleanest cut and the longest blade life. Forcing the cut generates excess heat, causes premature blade wear, and risks burning the sample. Too little force lets the blade glaze over and stop cutting effectively. Let the blade do the work.

Coolant

Continuous coolant flow is mandatory in abrasive cutting. It serves four jobs: it removes heat from the cut zone, flushes swarf and degraded abrasive away from the kerf, lubricates the cutting action, and prevents material from welding to the blade. For abrasive cutting specifically, the coolant should have a relatively high flash point, since abrasive cutting routinely produces sparks at the cut zone.

PACE supplies water-based abrasive cutting fluids formulated for metallographic work. For older cast-iron-base cutters, the right fluid also serves as a corrosion inhibitor.

Recommended PACE abrasive saws

PACE makes a complete line of MEGA abrasive cutters covering hands-on manual operation, manual table feeds, and fully automated production cutting.

MEGA-M250S, Economical Manual

250 mm wheel with manual wheel feed. The entry-point cutter for labs that need hands-on control on a budget.

MEGA-T250S / T300S / T350S / T400S, Manual Workhorses

Manual wheel and manual table feed in 250, 300, 350, and 400 mm wheel sizes. Step up the wheel size as your sample size grows.

MEGA-T300A / T350A / T400A, Automated

Programmed feed for repeatability, throughput, and operator safety. Best for high-volume labs and reproducible cut quality.

View the full MEGA abrasive cutter lineup →

Precision Wafer Cutting

Precision wafer cutting uses a thin diamond or cubic boron nitride (CBN) blade on a slow, micrometer-adjustable saw. The thin kerf, slow cutting action, and fine abrasive size produce cuts with minimal damage and very low material loss. It is the right method for delicate samples, precision-located cuts, and any material where sectioning damage would compromise the final microstructure.

When to use precision wafer cutting

• Brittle materials: ceramics, glass, semiconductors, minerals
• Thin samples or thin sections (under 1 mm)
• Composites with delicate fibers (boron, ceramic fiber, carbon-carbon)
• Bone, hard tissue, and biological samples
• Heat-sensitive materials
• Cuts that need to land at a specific feature (failure analysis, electronic components)
• Any application where damage and material loss must be minimized

Blade types

• Diamond, metal-bonded (rim-pressed): the most common precision wafering blade. Diamond particles pressed into a metal binder along the rim of the blade. Long life, broad applicability.
• CBN (cubic boron nitride): use instead of diamond for materials that dull diamond, especially high-carbon and heat-treated steels. Diamond reacts with iron at cutting-zone temperatures and degrades quickly; CBN does not.
• Electroplated diamond: single layer of diamond grit on a metal core, producing a much higher, rougher abrasive profile. Used for soft and "gummy" materials (bone, plastics, rubbery composites) where a smooth blade would clog.
• Thin resin-rubber abrasive on wafer saw: less common, but possible for some materials. Requires at least 3,500 RPM and frequent coolant changes (heavy debris generation).

Diamond and CBN blade selection

Three parameters define a wafer blade: abrasive size, abrasive concentration, and bond/blade type. Of these, abrasive size dominates damage performance, and concentration determines how much load the blade tolerates.

Concentration is expressed as a percentage. High Concentration (HC) ≈ 100%, Low Concentration (LC) ≈ 50%. PACE diamond wafer blades carry the WB- prefix with LC or HC suffix (for example, WB-0055LC = 5-inch diameter, low concentration). PACE CBN wafer blades use the WCBN- prefix. PACE electroplated diamond blades use WB-…EPD.

Two principles for picking grit and concentration

1. Finer abrasive = less damage. For extremely brittle materials (silicon, GaAs, glasses, ceramic composites, boron-graphite), a fine grit blade is often the only way to leave a microstructure that can be polished to truth. Coarser grits introduce damage that subsequent grinding may not fully remove.
2. Concentration scales with material toughness. Brittle materials (ceramics) cut better with low concentration: fewer cutting points, each carrying more load, which suits brittle fracture-driven cutting. Ductile materials (metals, plastics) cut better with high concentration: more cutting points spreading the load.

PACE WB-series diamond and WCBN-series CBN wafer blades.

PACE WB-…EPD electroplated diamond blades for soft and gummy materials.

Wafer cutting parameters by material

The table below collects PACE's recommended starting points for speed, load, and blade selection across material categories.

For the full PACE wafer blade catalog with stock and pricing, see the Precision Wafering Consumables page.

Wafer cutting procedure

1. Dress the blade with a ceramic dressing stick before cutting. (See Blade Dressing below for why this matters.)
2. Clamp the specimen firmly. If possible, clamp both sides of the specimen; this eliminates the cutting burr that otherwise forms at the end of the cut.
3. For brittle materials, clamp with a rubber pad between the jaws and the specimen. The pad absorbs cutting-zone vibration and protects the sample from fracturing.
4. Start the cut with reduced force to establish the kerf, then bring the load up to the target value once the blade is tracking cleanly.
5. Orient through the smallest practical cross-section. A shorter cut path means less time, less heat, and less risk of damage.
6. For coated samples, cut through the coating and exit into the substrate (coating in compression, the same rule as abrasive sectioning).
7. Use the largest blade flanges that fit your saw. Larger flanges support the thin blade and prevent wobble or flexing.
8. Reduce force at the end of the cut for brittle samples. The blade exiting the material is when end-fracture is most likely.
9. Use the appropriate cutting fluid (see below).

Blade dressing, what it actually does

Most operators dress wafer blades occasionally and assume they are "renewing the diamond." That is not what is happening. The diamond is still there. What is failing is the bond.

During cutting, the metal bond around each diamond particle smears slightly with each rotation. Over many cuts, the smeared bond blinds the cutting edge of the diamond, covering it and preventing it from biting into the workpiece. The cut rate drops with each successive cut. Dressing with a ceramic-abrasive-in-soft-matrix stick removes the smeared bond and exposes fresh diamond. After dressing, the blade cuts like new again.

Three rules for dressing:

• Always use a dressing fixture. Free-hand dressing chips and breaks blades.
• Light load: less than 200 grams. The goal is to abrade away smeared bond, not to grind the blade.
• Low speed: less than 300 RPM. Same reasoning.

Dress before each cutting session, and again any time cut rate begins to fall.

Wafer cutting fluid

Use a continuous coolant supply directed at the cut zone. Two families of cutting fluid are common:

• Water-based: easier to clean off samples and machine parts. Most common for routine wafer cutting.
• Oil-based: better lubrication, longer blade life on demanding cuts, but harder cleanup.

A good cutting fluid removes and suspends swarf, lubricates the blade-sample interface, and inhibits corrosion of the sample, blade, and machine. For reactive metals (magnesium, lithium, sodium alloys), use a non-aqueous fluid.

Recommended PACE precision wafering saws

PICO-155S and PICO-155P

Gravity-feed precision wafering saws. The 155S uses digital controls; the 155P uses analog. Both handle small samples with variable speed and load control.

PICO-200S, Manual Table Feed

Manual table-feed precision saw with capacity for larger or irregularly-shaped specimens. Best for high-accuracy research and industrial cuts that do not require automation.

PICO-200A, Automated Table Feed

Fully automated precision wafer cutting. Programmed feed for repeatable cut quality, ideal for production failure analysis and serialized samples.

View the full PICO precision wafering lineup →

Universal Best Practices

These habits apply to every cut, abrasive or precision.

Before the cut

• Mark the cutting plane on the sample clearly
• Clean the sample to remove surface contamination that could affect blade performance
• Verify the blade is properly mounted, balanced, and free of visible damage
• Check coolant level and condition; replace dirty fluid
• Wear appropriate PPE: safety glasses, hearing protection on abrasive cutters, gloves when handling sharp samples

During the cut

• Apply steady, consistent force; let the blade do the work
• Maintain continuous coolant flow over the cut zone
• Watch for excessive heat, smoke, discoloration, or unusual sounds; all are signs of a problem
• Do not force the cut. If it slows down, reduce force or check the blade rather than pushing harder
• For deep cuts, retract slightly to allow flushing and cooling, then re-engage

After the cut

• Let the sample cool before handling, especially after abrasive cutting
• Clean cutting fluid and swarf from the sample
• Inspect the cut surface for cracks, smearing, or burning
• Document the parameters that worked (and the ones that did not) for future reference
• Inspect the blade for wear or damage before storing

Blade and equipment care

• Store blades flat in a dry location; humid storage corrodes metal-bonded wafer blades
• Keep the saw hood open when the cutter is not in use to prevent corrosive humidity buildup
• Dress wafer blades before each session and any time cut rate drops (see Blade Dressing)
• Replace abrasive blades when cutting becomes inefficient or quality degrades; cracked or chipped blades are unsafe
• Keep a usage log so blade replacement schedules can be optimized

Troubleshooting

Most sectioning problems resolve with the same handful of adjustments: change the blade, change the force, change the coolant. Use the table below to narrow down the cause before reaching for a different blade.

What's Next: Mounting

Once your sample is cut, the next step is to mount it. Mounting holds the specimen at a known orientation, protects the edges during grinding, and gives the operator something to handle safely. Without mounting, the cut sample can deform under grinding pressure, edges round over, and small samples are unsafe to hold against an abrasive.

Continue to the Mounting Guide →