Precision for Machining, Inspection & Workshop Control

Precision work depends on knowing the dimension, not estimating it. Starrett measuring & inspection tools give machinists, fabricators, mechanical workshops, maintenance crews & quality-control teams the equipment to measure components, check tolerances, verify alignment & establish accurate workshop references.

Whether you're checking an outside diameter with a micrometer, measuring a bore, monitoring runout with an indicator or confirming squareness before machining, the instrument needs to match the feature being inspected. Explore Testing & Measurement Tools for broader workshop measurement equipment or Measuring & Layout Tools when the job starts with establishing dimensions, lines & reference points.

Starrett's precision range spans calipers, micrometers, indicators, bore gauges, depth gauges, height gauges, squares, precision rules, straight edges, hole gauges & angle-measuring tools, giving trades a choice between general dimensional checking & specialised inspection.

Start with what needs to be measured. Then choose the instrument capable of giving that measurement meaning.

What Are Starrett Measuring & Inspection Tools?

Precision Instruments for Measuring, Comparing & Verifying Components

Starrett has produced precision measuring tools since 1880, with its range built around dimensional measurement, inspection, layout & quality control.

Unlike general-purpose measuring equipment, precision inspection tools solve specific measurement questions.

► Slide calipers measure external, internal, depth & step dimensions depending on the instrument
► Micrometers provide dedicated close measurement across outside, inside, depth & specialised applications
► Dial & electronic indicators show small amounts of movement or dimensional variation
► Test indicators use a lever-style contact for comparative measurement, alignment & restricted-access inspection
► Bore gauges measure internal diameters & can help inspect bore condition
► Hole gauges provide practical methods for transferring or directly checking internal dimensions depending on the gauge type
► Depth gauges measure holes, slots, recesses & other features below a reference surface
► Height gauges establish measurements from a reference surface & can support layout, height transfer & inspection
► Squares check geometry, squareness & layout
► Precision rules & straight edges support dimensional, straightness & layout work
► Protractors & angle tools establish or inspect angular relationships
► Calipers, dividers & trammels transfer dimensions, establish arcs & support layout work

The right choice depends on dimension type, tolerance, measuring range, contact geometry, readout & inspection method.

Why Choose Starrett Measuring & Inspection Tools?

One Instrument Shouldn't Be Expected to Measure Everything

A slide caliper is versatile.

That versatility doesn't make it the correct instrument for every close-tolerance dimension.

A micrometer uses a dedicated measuring arrangement for precise dimensional checks. An indicator is designed to reveal movement or deviation. A bore gauge addresses internal geometry. A square checks a relationship between surfaces rather than simply returning a length.

Understanding those differences helps prevent one of the most common workshop measurement problems: using the instrument that's closest instead of the instrument the inspection requires.

Precision Measurement Is Part of Starrett's Foundation

Starrett's connection with precision measurement goes back to the development of the combination square by founder Laroy S. Starrett in the late 1870s.

The concept combined a graduated rule with an adjustable square head, creating a tool capable of handling several measuring & layout operations from one reference system.

That same practical idea still matters in a modern workshop: the measuring tool should make the inspection clearer, repeatable & useful to the next operation.

Match Capability to the Tolerance

More decimal places don't automatically mean a better measurement.

The useful instrument is one whose accuracy, resolution, range & measuring method suit the tolerance being checked.

Before selecting a precision tool, establish:

► What feature needs measuring?
► What tolerance must be verified?
► Is the measurement external, internal or depth?
► Is an absolute dimension required or a comparison against a reference?
► Does the workpiece require specialist contact geometry?
► Will readings need to be documented or transferred electronically?
► Is the instrument being used at the bench, on a machine or around installed equipment?

Those questions narrow the range more effectively than simply shopping by maximum measuring capacity.

Mechanical & Electronic Readouts Serve Different Workflows

Mechanical instruments remain practical where a direct analogue or vernier reading suits the operator & environment.

Electronic measuring tools provide a clear numerical display while selected Starrett instruments can support measurement-data output for manufacturing & quality-control workflows.

Choose according to how the measurement will actually be taken, interpreted & recorded.

Common Applications

Machining

A machining operation can only be corrected while enough material remains to make the correction.

Calipers provide fast dimensional checks during production.

Micrometers suit closer measurement of features such as thicknesses & diameters.

Indicators can help with machine setup, alignment, runout & comparative inspection.

Depth instruments address recesses, shoulders & holes while bore gauges provide a more purpose-built approach to internal diameter inspection.

For machine shops, the value isn't simply owning precision equipment — it's measuring at the stage where the result can still change the next cut.

Fabrication

Correct component length doesn't guarantee a correct fabrication.

Parts can still be out of square, misaligned or incorrectly positioned before joining.

Precision squares, rules, angle tools & suitable dimensional instruments allow fabricators to check the work before welding turns a setup error into rework.

Once dimensions & fit-up have been established, Welding Equipment supports the joining stage of the job.

Mechanical Maintenance

Wear isn't always obvious by sight or feel.

Shafts, bores, machine components & assemblies can require dimensional or comparative measurement to determine whether wear, movement or alignment remains within the required limits.

Calipers, micrometers, indicators & internal measuring instruments give maintenance teams actual information instead of relying solely on visual judgement.

For the surrounding bench, machine & maintenance environment, Workshop Equipment supports the broader workshop setup around inspection & repair.

Quality Control & Inspection

Inspection converts a measurement into a decision.

Is the component inside tolerance?

Has a bore reached the specified diameter?

Is a surface square to its reference?

Is the shaft running true?

Has a machined feature moved outside its allowable limits?

Depending on the question, the inspection method may involve calipers, micrometers, indicators, bore gauges, depth gauges, height gauges, precision squares or fixed references.

Consistency of technique becomes increasingly important as tolerances tighten.

Bench Layout

Not every precision tool is used after machining.

Rules, combination squares, dividers, trammels & angle-measuring equipment help establish dimensions, centres, straight lines, arcs & angular references before material is cut.

Secure workholding also matters when the component needs to stay fixed during measurement or marking. Clamps & Vises can support a more controlled bench setup.

Product Selection Guide

Start With the Feature You Need to Measure

Caliper or Micrometer?

This choice should be driven by the measurement rather than convenience.

A slide caliper is versatile because suitable models can measure external dimensions, internal dimensions, depth & steps.

A micrometer uses a more specialised measuring arrangement & is particularly relevant when closer dimensional measurement is required.

Use the caliper for the work it suits.

Move to a micrometer when the tolerance & measurement method call for it.

Outside, Inside or Depth Micrometer?

“Micrometer” covers several different instruments.

Outside micrometers measure external features such as thickness or shaft diameter.

Inside micrometers measure internal dimensions such as bores & slots.

Depth micrometers measure recesses, shoulders & depth features.

Starrett also produces specialist micrometer configurations for particular workpiece geometries.

Identify the feature before choosing the micrometer.

Gauge & Inspection Tools

A gauge becomes useful when the inspection question moves beyond a straightforward outside measurement.

Bore gauges are designed around internal diameter measurement. Depending on the gauge, they can also help an operator evaluate variation within a bore rather than relying on one isolated reading.

Small-hole & telescoping gauges can transfer an internal dimension so it can be checked with another suitable measuring instrument.

Depth gauges reference from a surface to measure holes, slots, recesses & shoulders. Starrett's depth-measurement range includes rule, vernier, dial, electronic & micrometer-based approaches.

Height gauges work from a reference surface such as a surface plate. They can be used for height measurement, layout, transferring dimensions & checking relationships between features.

The important distinction is direct measurement versus transferred or comparative measurement. Know which result the gauge provides before building an inspection method around it.

Dial Indicator or Test Indicator?

Both detect small movement, but they operate differently.

A conventional dial indicator generally uses a plunger moving linearly. These instruments are commonly mounted to a suitable fixture or magnetic base for comparative checks, machine adjustment & runout measurement.

A test indicator uses a lever-style contact that moves through an arc.

That contact arrangement can be useful for alignment work, small bores, narrow grooves & positions where a conventional plunger is difficult to locate.

Dial, Vernier or Electronic?

Each readout has a place.

Vernier: mechanical, battery-free & suited to operators comfortable reading a graduated scale.

Dial: provides an analogue visual indication that can be useful when monitoring changing movement.

Electronic: gives a direct numerical display while selected instruments can integrate with measurement-data collection systems.

Don't choose electronic simply because it's electronic. Choose it where the readout or data workflow provides a genuine advantage.

Which Square?

Starrett's connection with the combination square isn't just a brand-history detail — the tool remains highly practical for workshop measurement & layout.

A combination square uses an adjustable head along a graduated rule, allowing one tool to perform several operations including square, 45-degree, depth, height & layout work.

A solid precision square moves towards dedicated squareness inspection.

A double square provides an adjustable compact format suited to machining, toolmaking, layout & bench work.

Match the square to whether you're laying out the work, transferring a reference or inspecting its geometry.

Expert Tips

Don't Confuse Resolution With Accuracy

A display containing another decimal place doesn't automatically make the measurement more accurate.

Resolution tells you how finely the instrument displays or divides a measurement. Accuracy describes how closely that result represents the actual dimension.

Select both around the job.

Clean the Contact Points Before Measuring

Swarf, oil, dust or other contamination between a measuring face & component can influence a precision reading.

Clean the relevant contact surfaces before treating the result as meaningful.

Let the Instrument Sit Correctly on the Feature

A caliper or micrometer held at an angle can give a misleading measurement.

Establish proper contact with the workpiece & check that the instrument is aligned with the feature being measured.

Use Consistent Measuring Force

More pressure doesn't create more accuracy.

Excessive measuring force can affect technique, the workpiece or the reading.

Where a micrometer incorporates a ratchet, friction thimble or another force-control method, use it as intended.

Consider Temperature on Close-Tolerance Work

Machined components can carry heat from the cutting process while measuring tools can absorb heat from handling or the surrounding environment.

As tolerances become tighter, measurement conditions matter more.

Allow the inspection process to suit the precision expected from the result.

Check More Than One Point Inside a Bore

A single internal measurement doesn't necessarily describe the whole bore.

Where the job requires it, take readings at appropriate positions & depths to investigate dimensional variation rather than assuming one point represents the complete feature.

Start Height Measurement With the Reference Surface

A height gauge only becomes useful when its reference is trustworthy.

Keep the base & working surface clean, establish the required zero or reference correctly & avoid allowing debris beneath the gauge to become part of the measurement.

Use the Correct Instrument Instead of Making the Caliper Do Everything

Calipers earn their place in workshops because they're extremely useful.

That doesn't turn them into universal substitutes for micrometers, indicators, bore gauges, height gauges or dedicated inspection tools.

When the tolerance or feature calls for a specialised instrument, change instruments.

Protect Precision Tools Between Measurements

A precision micrometer shouldn't live loose underneath files, punches, grinding debris & general workshop hardware.

Protect measuring faces, contacts, spindles, scales & mechanisms during storage.

How To Clean Your Gear Without Ruining It covers practical care principles for equipment exposed to workshop conditions.

Inspect Before the Next Operation Makes the Error Expensive

Measure before the next cut.

Check squareness before welding.

Confirm the bore before assembly.

Inspect alignment before returning the machine to service.

Precision measurement creates the most value when the result arrives early enough to change the outcome.

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