Which Is Rougher: 120 Grit or 220 Grit?

Choosing between P120 and P220 begins with purpose, not with a claim that one grade produces a fixed surface value. P120 is the rougher grade and provides greater cutting capacity, while P220 creates a finer, more uniform scratch after major defects have been removed. The appropriate choice depends on whether the task is still removing material or is preparing the surface for the next finishing stage.

Quick Answer: P120 is rougher than P220. Use P120 when meaningful defect removal, leveling, or scratch refinement is still required. Choose P220 when the major defects are gone and the process calls for a finer, more uniform scratch. A direct P120-to-P220 progression can work, but hard substrates and appearance-critical finishes may benefit from P150 or P180 between them.

Neither grit defines a fixed Ra or guarantees a particular finish. Substrate, abrasive construction, tool settings, technique, loading, wear, and the intended coating all influence the finished surface. The sound endpoint is therefore application-specific: follow the relevant preparation instructions, clean and inspect between grades, and use a sample panel when appearance or coating behavior matters.

Why Doesn’t Each Grit Have a Fixed Ra?

There is no fixed Ra value because finished roughness changes with the substrate, mineral, grain shape, coat density, backing, tool orbit and speed, pressure, sanding direction, extraction, abrasive wear, measurement method, and profilometer settings. Without those conditions, assigning one Ra to P120 and another to P220 is incomplete. Grit identifies a process input; it does not specify the resulting finished surface.

Why Doesnt Each Grit Have a Fixed Ra: a practical view of the relevant sanding setup and surface condition.

Ra should not be assigned to an abrasive grade as though the grit number directly defines the finished surface. P120 and P220 identify process inputs, but the profile left after sanding is created by the interaction of the abrasive, workpiece, tool, operating conditions, and measurement procedure. Changing any of those conditions can change the reported roughness even when the grit designation remains the same.

The substrate affects how grains penetrate, cut, and deform the surface. Mineral type and grain shape influence the cutting action, while coat density changes how many cutting points contact the work. Backing construction affects how the abrasive conforms and supports those grains. Tool orbit and speed, applied pressure, sanding direction, and extraction further alter contact and debris removal. As the abrasive wears, its cutting behavior also changes, so a fresh product and a worn product of the same grade need not leave an identical profile.

Measurement adds another layer of dependency. The method used to measure the surface and the selected profilometer settings¹ affect the value reported as Ra. A comparison between P120 and P220 is therefore incomplete if it omits the substrate, abrasive construction, operating conditions, abrasive condition, measurement method, or instrument settings. A defensible specification should distinguish the selected grit from the required finished-surface condition. Grit may help control the process, but it cannot, by itself, serve as a finished-surface specification or guarantee one Ra value.

When Should You Choose P120?

P120 is appropriate while meaningful defect removal remains necessary. Typical applications include leveling bare wood, refining scratches left by a coarser grade, removing light corrosion, smoothing a suitable primer, and preparing automotive filler for the next stage. Its greater cutting capacity removes defects more effectively than P220, but its scratch may remain visible beneath a thin transparent, dark, or glossy finish.

When Should You Choose P120: a practical view of the relevant sanding setup and surface condition.

P120 is the appropriate choice when the surface still needs meaningful defect removal. Its function at this stage is to cut more effectively than P220, so it can continue correcting the surface instead of merely refining it. The decision should be based on the remaining defect and the next process stage, not on a general preference for a smoother feel.

On bare wood, P120 can be used for leveling when the surface still requires correction. After a coarser grade, it can refine the marks left by that earlier step and prepare the work for subsequent refinement. It is also suited to removing light corrosion, smoothing a primer that is appropriate for sanding, and preparing automotive filler for the next stage. Each use has the same process logic: enough cutting capacity is still needed to reduce the existing defect efficiently.

That cutting capacity also defines the limitation of P120. Its scratch can remain visible beneath a finish that is thin, transparent, dark, or glossy. Visibility is therefore especially relevant when the next layer will not conceal the sanding pattern. P120 should complete the required defect-removal work, but it should not automatically be treated as the final preparation grade. Once the major correction is complete, the process can move to a finer abrasive as required by the intended finish. This keeps P120 in its proper role: meaningful removal and refinement of coarser marks before final surface preparation.

When Is P220 Better?

P220 is better after major defects are removed and a finer, more uniform scratch is needed. It suits selected final raw-wood refinement, light scuff sanding between compatible coating layers, or preparation specified by the coating manufacturer. Used too early, it shapes inefficiently and may load rapidly. Greater smoothness does not guarantee adhesion; required profiles and recoat instructions must govern between-coat sanding.

When Is P220 Better: a practical view of the relevant sanding setup and surface condition.

P220 is better suited to refinement than to major correction. It becomes appropriate after the principal defects have been removed and the required task is to leave a finer, more uniform scratch. Starting with that condition is important because P220 is inefficient for shaping or substantial defect removal. If introduced too early, it may also load rapidly rather than complete the necessary correction efficiently.

Suitable uses include final refinement of raw wood in selected systems, light scuff sanding between compatible coating layers, and surface preparation specifically required by a primer, paint, or clear-coat manufacturer. These uses are conditional rather than universal. The material and finishing system must call for the finer scratch, and the preparation instructions should determine whether P220 is an appropriate endpoint or an intermediate step.

A smoother surface should not be treated as an automatic improvement in adhesion. Some coatings and adhesives require a defined surface profile, so reducing the scratch without reference to that requirement can move the surface away from the needed preparation. Between coating layers, recoat instructions also govern the sanding operation. Following them helps avoid cutting through a layer or compromising the chemical adhesion available within the specified recoat process.

The practical choice is therefore sequence-dependent. P220 follows defect removal; it does not replace it. Use it when the surface already has the needed shape and the next operation calls for controlled refinement. Where coating or adhesive performance is involved, the manufacturer’s profile and recoat directions take precedence over the assumption that finer sanding is always preferable.

Can You Sand Directly from P120 to P220?

A direct P120-to-P220 sequence can work, but it must be tested. On hard substrates or appearance-critical work, adding P150 or P180 often removes P120 scratches more efficiently. Limiting a grit jump to roughly 1.5 times is only a heuristic because grit scales and product constructions are not linear. Clean between grades, inspect under low-angle light, and coat a test panel to reveal residual scratches.

Can You Sand Directly from P120 to P220: a practical view of the relevant sanding setup and surface condition.

A direct move from P120 to P220 is possible, but the acceptability of that sequence has to be verified on the actual work. The important question is whether P220 removes the P120 scratch efficiently enough for the required appearance. A successful sequence on one substrate or product construction should not be assumed to behave the same way in another setting.

Hard substrates and appearance-critical work often benefit from an intermediate P150 or P180 step. That intermediate grade can remove the P120 scratch more efficiently before P220 creates the finer final pattern. Adding a step is therefore useful when the direct jump leaves visible marks or requires inefficient refinement. Where the direct sequence clears the earlier scratch and meets the finish requirement, the intermediate grade may not be necessary.

The common suggestion that a grit jump should be limited to roughly 1.5 times is only a heuristic. It is not an industry standard, and grit-number scales are not linear². Product constructions also differ, so arithmetic applied to the printed grade cannot determine by itself whether one abrasive will remove the preceding scratch.

Verification should include cleaning the surface between grades and inspecting it under low-angle light. The intended stain, paint, or clear finish should also be applied to a sample panel, because some residual scratches may become visible only after coating. The acceptable sequence is the one that removes the earlier pattern efficiently and remains acceptable under the intended finish.

Can P220 Make Wood Too Smooth?

P220 can make raw wood unnecessarily smooth or undesirable for some staining systems. Fine sanding may burnish fibres and alter liquid stain uptake, but species, density, earlywood and latewood structure, prior machining, stain chemistry, and application method all affect the result. P220 does not always cause blotching. Sample panels should determine the sanding endpoint that delivers the required colour, clarity, and adhesion.

Can P220 Make Wood Too Smooth: a practical view of the relevant sanding setup and surface condition.

P220 can leave raw wood smoother than a particular staining system needs, but that does not make it universally unsuitable. Fine sanding may burnish the fibres and change how a liquid stain is taken up. Whether that change is desirable, negligible, or problematic depends on the wood and the complete finishing method rather than on the grit number alone.

Species and density influence the way the surface responds to sanding and stain. The relationship between earlywood and latewood adds another source of variation within the wood structure. Previous machining also matters because the surface reaching the P220 stage has already been shaped by earlier operations. Stain chemistry and application method then influence how the prepared surface accepts and displays the liquid stain. These variables prevent a single sanding endpoint from governing every raw-wood staining process.

It is therefore too broad to state that P220 always causes blotching. In some systems, stopping at P220 may be unnecessary or may create an undesirable level of smoothness; in others, it may provide the required refinement. The relevant question is not whether P220 is inherently too fine, but whether it supports the specified colour, clarity, and adhesion for that combination of wood, stain, and application method.

Sample panels provide the appropriate basis for selecting the endpoint. Prepare them with the intended sanding and staining process, then compare which endpoint delivers the required colour, clarity, and adhesion. The selected grade should follow that application-specific assessment rather than a universal rule about smoothness or blotching.

Do Standards and Product Construction Matter?

Standards and product construction matter because FEPA P120 and P220 are not automatically equivalent to unprefixed ANSI/CAMI products. Abrasives of one grade can cut differently when made with aluminum oxide, silicon carbide, ceramic, or another mineral. Paper, film, cloth, screen, and net backings present grains differently. Production specifications should identify the standard, mineral, backing, coat structure, dimensions, and tool parameters.

Do Standards and Product Construction Matter: a practical view of the relevant sanding setup and surface condition.

The abrasive grade must be read together with the standard behind it. FEPA P120 and P220 are not automatically identical to products marked with unprefixed ANSI/CAMI grades³. A shared or similar number therefore does not establish equivalence across those systems. Naming the standard prevents the grade designation from being interpreted as though every numbering system describes the same abrasive.

Product construction matters within a grade as well. Aluminum oxide, silicon carbide, ceramic, and other minerals do not cut in the same way. The backing also changes how the grains are presented to the work. Paper, film, cloth, screen, and net constructions can therefore produce different cutting behavior even when the stated grade is the same. Coat structure adds another relevant construction variable because it helps define how the abrasive surface is arranged.

For a production specification, the grit label alone is incomplete. The specification should identify the applicable standard, mineral, backing, coat structure, and abrasive dimensions. It should also state the tool parameters used with the product. Together, those details define the intended process more clearly than a number such as P120 or P220 in isolation.

This level of detail is necessary because matching only the printed grade can overlook differences in the standard and physical construction that affect cutting action. A controlled description retains the grade but also records the attributes that give it practical meaning. P120 and P220 remain useful identifiers, provided they are tied to the correct standard and to the mineral, backing, coat structure, dimensions, and tool parameters of the intended abrasive system.

How Do Loading and Wear Affect Cost?

Loading does not convert P120 into a controlled P220 tool; it causes rubbing, increases heat, and produces an inconsistent scratch. Abrasives should be cleaned or replaced only as their manufacturer permits, with extraction and anti-loading constructions used where appropriate. An economical sequence typically uses P120 for defect removal and P180 or P220 for refinement, while cost evaluation includes sanding time, consumption, rework, rejects, and downstream finishing per accepted part.

How Do Loading and Wear Affect Cost: a practical view of the relevant sanding setup and surface condition.

Loading is a change in abrasive condition, not a controlled change in grit. A loaded P120 product does not become the equivalent of P220. Instead, the loading makes the abrasive rub, raises heat, and leaves an inconsistent scratch. Continuing to use it as though it had simply become finer removes control from the process and can undermine both defect removal and surface refinement.

The response to loading should remain within the abrasive manufacturer’s instructions. Clean the product only when the manufacturer permits that method, and replace it when continued use is no longer permitted or appropriate. Extraction can help manage the process where it is suitable, while anti-loading constructions can be selected where they are appropriate. Neither measure changes the basic rule that a loaded abrasive should not be treated as a predictable finer grade.

An economical sequence assigns each grade to the work it performs effectively. P120 normally handles defect removal, after which P180 or P220 provides refinement. This division avoids relying on worn or loaded P120 to create the later-stage scratch. Wear must be managed as abrasive condition changes, rather than used as an informal substitute for selecting the required refinement grade.

Cost should be assessed per accepted part, not from abrasive consumption alone. The evaluation includes sanding time, abrasive consumption, rework, rejects, and downstream finishing cost. A product that appears economical when only consumption is considered may be less economical once inconsistent scratches, added sanding, or finishing consequences are included. The useful comparison is the complete process cost associated with producing an accepted part through the specified defect-removal and refinement sequence.

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P120 is rougher and better suited to meaningful defect removal; P220 is finer and belongs after the major defects have been removed. Neither grade guarantees a fixed Ra, because the substrate, abrasive construction, sanding conditions, wear, and measurement method influence the finished surface. The sequence may move directly from P120 to P220 or use P150 or P180 between them when the earlier scratch needs more efficient removal. The sanding endpoint should follow the intended coating or staining requirements, the relevant grit standard, and a clean inspection or sample panel. Loading should trigger permitted cleaning or replacement, not be treated as controlled refinement.

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