Industries Information

 Thread gages are dimensional instruments for measuring thread size, pitch or other parameters.  A variety of thread gaging instruments and tools exist such as measuring wire, tri-roll comparators, thread plug gages, thread ring gages and thread micrometers.  The appropriate variable or fixed limit gage for an application should be selected based on internal and external thread type, specific thread designation (UNS, UNF, UNC, NPT, ACME, Buttress), part tolerances and gaging frequency (shop vs. high volume production).

Thread gages can be one of any number of types of gages.  These in clued plug, ring, 3-wire, micrometer, tri-roll comparator, measuring wire, screw thread insert (STI), and thread gaging roll thread gages.  Thread plug gages measure go / no-go assessment of hole and slot dimensions or locations compared to specified tolerances.  Thread ring gages measure go / no-go assessment compared to specified tolerances of the dimensions or attributes of pins, shafts, or threaded studs.  3-wire thread gages are gages that use thread wires to gage thread size with one wire mounted in one holder and two wires mounted in a second holder.  The holders are placed in the measuring gage and brought in contact with the threads.  Thread micrometers are micrometers for measuring thread.  A tri-roll comparator is a specialized thread gage employing three thread rolls and a digital or dial display.  The thread gaging rolls can be interchanged to measure different thread sizes.  A measuring wire is a specialized wire manufacturing to precise gage sizes for measuring external threads.  The wire is wrapped or placed in the thread cavity and then a measurement is made with a micrometer or other OD gage.  STI gages, also referred to as helical coil or helicoil, are used where a screw thread insert will be used.  STI gages are widely applied in the automotive industry.  Thread gaging rolls are threaded rolls for use on roll thread comparators.

Different thread types, profiles ,and geometries provide different functionalities.  Thread designations include UNC, UNF, UNEF, UN, M/MJ (metric), NPT, NPTF, NPSF, ANPT, BSPT, BSPP, ACME, and buttress.  Thread gages measure the size or diameter of the feature being measured.  English pitch is the threads per inch that the gage can measure.  Metric pitch is the metric thread spacing that the gage can measure.

Common shapes or geometries measured include cylindrical and tapered or pipe.  A go gage provides a precision tool for production comparative gaging based on a fixed limit.  Go gages consist of a fixed limit gage with a gaging limit based on the plus or minus tolerances of the inspected part.   No-go or not-go gages provide a precision tool for production comparative gaging based on a fixed limit. No-go gages consist of a fixed limit gage with a gaging limit based on the minimum or maximum tolerances of the inspected part.   Go / no-go gages configured with a go gage pin on one end and a no-go gage pin on opposite end of the handle. Go / no-go gages provide a precision tool for production comparative gaging based on fixed limits.  Go / no-go gages manufactured in the form of stepped pins with the go gage surface and the no-go gage surface on the same side of the handle.  The gage can save type in gaging since the gage does not have to be reversed for no go gaging.  Master gage blocks, master or setting discs, and setting rings are types of master gages used to calibrate or set micrometers, comparators, or other gaging systems.  Fixed limit or step gages are specialized thread plug gages for gaging taper pipe threads.  Notches or external steps indicate maximum and minimum allowable tolerances.  Tolerance classes for thread gages include Class XX, Class X, Class Y, Class Z, Class ZZ and thread Class W.

Measurement units for thread gages can be either English or metric.  Some gages are configured to measure both.  The display on the gage can be non-graduated meaning that the gage has no display, dial or analog, digital display, column or bargraph display, remote display, direct reading scale, or Vernier scale.

 Squares are used to indicate if two surfaces of a part or assembly are perpendicular by visual comparison.  Most squares consist of a simple, fixed standard with a beam and blade (or two surfaces) with a mutual orientation of 90 degrees.  A wide variety of squares exist such as precision/solid square, cylindrical squares, adjustable universal / sliding bevel, adjustable die maker’s square, angle squares, double squares, try squares, "T" squares and combination squares.

Precision or solid squares consist of a short ground blade and a beam or handle section that form an "L" shape. The squares are precision ground and do not normally have any rulings.  The square often has reliefs on the inside corners or outside edge to facilitate the fillets or radii on cast or machined parts. The beam is thicker compared to the blade, which facilitates location of the square on an edge. Solid squares are used for precision marking, measuring and checking squareness of components in machine shop settings.

Cylindrical squares have a hollow cylindrical shape and are commonly used to check other squares in machine shop or inspection room settings.  Some cylindrical squares will provide graduations indicating the variation from square.

Universal bevels, sliding bevels, combination bevels, or T-bevels are used to transfer or duplicate angle measurements.  Usually, bevels do not have any graduations.

Adjustable die makers’ squares are used to measure small angular variations (10 degrees) from square. These squares are commonly used for measuring angles, die clearances, and pattern drafts.  They often come with different attachments such as offset, bevel, or ruled blades.

An angle square consists of a square with angular graduations along the longest face or hypotenuse.

Double precision squares have a square head that slides onto a blade or rule.  The square head has two square surfaces and usually a variety of optional blade types such as bevel blades, drill point angle blades, and ruled blades.

Try squares consist of a short blade and a beam or handle section that form an "L" shape. The beam is thicker compared to the blade, which facilitates location of the square on an edge.  "L" squares are used for general shop marking, measuring, and checking squareness of components.

"T" or dry wall squares have a long blade and a beam or handle section that forms the top of the "T" shape. The beam is thicker compared to the blade, which facilitates location of the square on an edge.  "T" squares are used for marking, measuring and checking squareness of large flat sheets of materials such as drywall.  "T" squares are available in fixed or folding versions.

Combination squares measure length, center, angular or squareness determination, and often have transfer or marking capability.  These multiple tasks are possible because these sets have a series of optional heads (square, center or protractor).

Snap gages are used in production settings where specific diametrical or thickness measurements must be repeated frequently with precision and accuracy.  Snap gages are mechanical gages that use comparison or the physical movement and displacement of a gaging element (e.g., spindle, slide, stem) to determine the dimensions of a part or feature.  In this case, snap gages are similar to micrometers, calipers, indicators, plug gages, and ring gages.  Snap gages are for both English and metric measurement configurations.

Snap gages are available in fixed and variable forms.  The variable forms often have movable, top sensitive contact attached to an indicator or comparator. The nonadjustable or fixed limits forms typically have a set of sequential gaps for go / no-go gaging of product thickness or diameter.  

Fixed limit snap gages are factory set or are otherwise not adjustable by the user.  A common example of this type of device is the AGD fixed limit style snap gage. These gages are set to go and no-go tolerances. A snap gages’ go contact dimensions are based on the maximum tolerance of the round bar, thickness or part feature being gaged.  No-go contact dimensions are based on the minimum tolerance of the round bar, thickness, or part feature being gaged by the snap gage.

Variable, or top sensitive contact, snap gages use a variable contact point that moves up during part gaging.  The contact point moves providing a go to no go gaging range.  The top contact is normally connected to a dial indicator that provides visual indication of any diametrical or thickness variations.

There are a number of optional snap gage features that can aid in gaging speed or extending the measurement range of a particular snap gage.  These features include interchangeable anvils, locking and back or part support.  Snap gages having replaceable anvils, contact points, styli, spindles, or other contacting tips or faces allow for gaging of many different items easily.  Back or part support involves a protrusion or stem located behind a part to hold or stop the part from moving past a certain point during gaging.  Similarly, lockable devices have a slide or spindle on the gage that can be locked in a fixed position.  Both of these features can be used to quickly foster go / no-go gaging.

 Rules are flat, graduated scales used for length measurement.  Rules and scales are available in variety of forms such as rigid or flexible rules, electronic linear scales, folding rules, drill point gages, tape measures and rule depth gages.  Rules generally provide an approximate measurement compared to precision gages.  However, digital or electronic linear scales designed for OEM machine tool applications and provide a high degree of accuracy.

Rules and scales fall into the general category of measuring tools.  Measuring tools are instruments and fixed gages that provide comparative and quantitative measurements of a product’s or component’s dimensional, form and orientation attributes such as length, thickness, level, plumbness and squareness.  Measuring or shop tools include rules, linear scales, recticles protractors and angle gages, level and inclinometers, squares and fixed gages.  Measuring tools are used in construction and building (contractors), drafting and drawing (designers), machine shops and tool rooms (machinists), field work (surveyors) and offices.

Reticles are optical scales used in conjunction with microscopes or magnifiers to measure fine details.  Measuring tapes are used measurements of large structures or features in buildings, plants and field work.   Specialized rules or scales are available such as short rules for length measurement in a cavity or shrink rules for pattern making in foundries.

 Ring gages are used for go / no-go assessment compared to the specified dimensional tolerances or attributes of pins, shafts, or threaded studs.  Ring gages are used for comparative gaging as well as for checking, calibrating or setting of gages or other standards.  Individual ring gages or ring gage sets are made to variety of tolerance grades in metric and English dimensions for master, setting or working applications.  Rings are available in plain (smooth, unthreaded), threaded, cylindrical and tapered forms to go, no-go or nominal tolerances.  There are three main types of ring gages: go, no go, and master or setting ring gages.

Go ring gages provide a precision tool for production comparative gaging based on a fixed limit.  Go gages consist of a fixed limit gage with a gaging limit based on the plus or minus tolerances of the inspected part.  A go ring gage’s dimensions are based on the maximum OD tolerance of the round bar or part being gaged. A go plug gage’s dimensions are based on the minimum ID tolerance of the hole or part being gaged.  The go plug (ID) gage should be specified to a plus gagemakers’ tolerance from the minimum part tolerance.  The go ring (OD) gage should be specified to a minus gagemakers’ tolerance from the maximum part tolerance.

No-go or not-go gages provide a precision tool for production comparative gaging based on a fixed limit. No-go gages consist of a fixed limit gage with a gaging limit based on the minimum or maximum tolerances of the inspected part.  A no-go ring gage’s dimensions are based on the minimum OD tolerance of the round bar or part being gaged.  The no go ring (OD) gage should be specified to a plus gagemakers’ tolerance from the minimun part tolerance.

Master and setting ring gages includes gage blocks, master or setting discs, and setting rings are types of master gages used to calibrate or set micrometers, comparators, or other gaging systems.  Working gages are used in the shop for dimensional inspection and periodically checked against a master gage.

 Protractors and angle gages measure the angle between two surfaces of a part or assembly.  Fixed angle gages, universal protractors, combination sets, protractor heads, sine bars, and "T" bevels are used for angular measurement.  Protractors and angle gages fall under the category of measuring tools.  Measuring tools are instruments and fixed gages that provide comparative and quantitative measurements of a product or component’s dimensional, form and orientation attributes such as length, thickness, level, plumbness and squareness.  Measuring or shop tools include rules, linear scales, protractors and angle gages, level and inclinometers, squares and fixed gages.  Measuring tools are used in construction and building (contractors), drafting and drawing (designers), machine shops and tool rooms (machinists), field work (surveyors) and offices.

Types of protractors and angle gages available include angle square, rule depth or angle gage, combination set or square, fixed angle gage, protractor head, rectangular or semicircular head protractor, sine bar or block or plate, universal or sliding bevel, and universal or bevel protractor.  An angle square consists of a square with angular graduations along the longest face or hypotenuse.  A rule depth or angle gage is a combination rule with an attachment for indicating the depth orientation of the hole with respect to the top surface.   Combination squares measure length, center, angular or squareness determination, and have transfer or marking capability.  These multiple tasks are possible because these sets have a series of optional heads (square, center or protractor).  Fixed angle gages have a series of fixed angles for comparative assessment of the angle between two surfaces.  Protractor heads are an attachment or an optional part of a combination square set.  The protractor head slides onto the steel rule and provides a tool for angular measurement or transfer.  Rectangular or semicircular head protractors have a long, thin, unruled blades and heads with direct reading angular graduations.  Sine bars, blocks, tables, or plates are used for precision angular measurement and are used in machine shops, tool rooms or inspection labs.  Trigonometric calculations are used to determine the angles.   Universal bevels, sliding bevels, combination bevels, or T-bevels are used to transfer or duplicate angle measurements.  Usually, bevels do not have any graduations.  Universal or bevel protractors have a base arm and blade with a wide angular range.  Bevel protractors have a graduated, angular direct reading or Vernier scale located on a large disc.  Protractors and angle gages can be level sensing or inclinometers.  Mechanical or electronic tools that indicate or measure the inclination of a surface relative to the earth’s surface usually in reference to horizontal (level), vertical (plumb) or both axis.

Important specifications to consider when searching for protractors and angle gages include angular range and angular resolution.  There are many choices for scales or displays on protractors and angle gages.  These include none or non-graduated, audible indicator or buzzer, column or bar graph, dial, digital display, direct reading scale, remote display, and Vernier scale.  Features for protractors and angle gages include machine or instrument mounted, certificate of calibration, locking feature, marking capability, and linear ruled protractor.  Common materials of construction for protractors and angle gages include aluminum, brass or bronze, cast metal or iron, plastic, fiberglass, glass, granite, stainless steel, steel, and wood.

Plug and pin gauges are used to compare hole and slot dimensions or locations to specific tolerances. There are several basic types of products. Go gauges and no-go gauges are fixed limit gauges with gauging limits based on the plus or minus tolerances of inspected parts.  Go gauge dimensions are based on the minimum inside diameter (ID) tolerance of the inspected part. No-go gauge dimensions are based on the minimum outside diameter (OD) tolerance of the inspected part. Double-ended go/no-go gauges include a go gauge pin on one end of a handle and a no-go gauge pin on the opposite end. Progressive or step go/no-go gauges have stepped pins with the go gauge surface and the no-go gauge surface on the same side of the handle. Master gauge blocks, master or setting discs, and setting rings are master gauges used to calibrate or set working plug or pin gauges. Working devices are used for dimensional inspection and checked periodically against a master gauge. Annular plug gauges are large, usually over 8” in diameter, and used to set or check micrometer or other OD gauges. Some plug and pin gauges have internal or external threads for gauging threads parts or part features. Others are packaged in a kit with adjustment tools such as alternate extensions and contact tips, holders, and bases.

Plug and pin gauges use several different gauging technologies. Pneumatic systems measure the changes in flow or pressure in air nozzles or inlets located inside air plugs, rings, or snaps. Pneumatic comparators, digital readouts, analog amplifiers, columns, and flowmeter/rotameter tubes are used to display dimensional data. Electronic gauges use linear variable differential transformers (LVDTs), capacitive, inductive or other electronic probes to sense the distance of displacement of a contact or stylus. Mechanical gauges use comparison or the physical movement and displacement of a gauging element (e.g., spindle, slide, stem) to determine the dimensions of a part or feature.  Micrometers, calipers, indicators, plug gauges, ring gauges or snap gauges are examples of mechanical gauges. These devices may use an integral electronic probe in addition to the mechanical gauging elements.

There are several geometries and holder/handle types for plug and pin gauges. Cylindrical plug and pin gauges have a tubular shape and no taper. Tapered devices have a conical form. Pin and plug gauges with ball-shaped ends are used to gauge spherical cavities and tapered holes. Hex or nut gauges have hexagonal or square cross- sections for gauging countersunk holes that lock nut or bolt heads in place during fastening. Plain gauges with smoother outer surfaces and bores are also available. There are three holder/handle mounting types. Taperlock gauges fit a tapered cavity in the handle. Trilock gauges have a central hole for a fastener that attaches the gauge to the handle. Reversible gauges allowing both ends of a gauge to be used. When one end becomes worn, the gauge is reversed in the holder. Some devices have heat-insulating, plastic handles.   

Specifications for plug and pin gauges include plug size or diameter, set range, and set steps or increments. Suppliers specify products according to metric or English (imperial) measurements. Tolerance class is an important consideration. Class XX gauges range in size from .001" to 0.08250" and have a tolerance of no more than 0.00002". Class X gauges range in size from .001" to 0.08250" and have a tolerance of no more than 0.00004". Class Y gauges range in size from .001" to 0.08250" and have a tolerance of no more than 0.00007". Class Z gauges range in size from .001" to 0.08250" and have a tolerance of no more than 0.0001".

Mechanical micrometers are instruments for precision dimensional gaging consisting of a ground spindle and anvil mounted in a C-shaped steel frame.  Noncontact laser micrometers are also available. Mechanical micrometers are available in Vernier scale, digital and dial variations. Micrometers provide precise, quantitative measurements of a product’s or component’s attributes such as thickness, depth, height, length, I.D., O.D., roundness or bore.  Specialized micrometers are available for the measurement of threads, gear teeth and tube wall thickness.  Laser micrometers are especially effective in inline gaging applications of high speed materials.

Common micrometer types include external, internal, bore, height, laser, micrometer head, and thread.  External micrometers are capable of measuring an outer diameter (OD) or outside feature of a part or component.  Internal micrometers are capable of measuring an inner diameter (ID) or inside feature or cavity of a part or component.  Bore micrometers have the ability to measure the inside diameter of a hole, bore, or blind hole at shallow to very deep (~0.03m inches to several feet) depths into the bore.  Height micrometers are tailored for height measurement.  Laser micrometers use optical, laser, or video-based technology to measure dimensional features.  Micrometer heads or jig borer micrometers consist only of the spindle and drum portion (no frame or anvil).  Micrometer heads are OEM components built into microscopes, machine tools, medical equipment or other metrological systems to provide precision measurement or positioning.  Jig borer micrometers and end measuring rods (fixed standard) are commonly used to set spacing and table locations.  Thread micrometers are designed for measuring thread size, pitch, or other parameters.  Micrometers can be available in sets of several gages and accessories packaged into a kit usually in a case with adjusting tools. Tool kits sometimes contain alternate extensions and contact tips, holders, bases, or standards.

Important parameters to consider when specifying micrometers include range and resolution.  The range of the micrometer is the total range length or dimensional range that the gage can measure.  The resolution is the best or minimum resolution for gages with digital displays.  Measurement units for micrometers can be either English or metric.  Some micrometers are configured to measure both.  The display on the micrometer can be non-graduated meaning that the micrometer has no display, dial or analog, digital display, column or bargraph display, remote display, or Vernier scale.

Micrometers come with cylindrical anvils and spindles with flat carbide or hardened steel contacting faces.  Specialized anvils or spindles are also available, these include ball anvil, blade or spade anvil, flange of disc (gear tooth), pin or reduced face, point anvil (thread gaging), or v anvil or 3-point.  Mounting options for micrometers include handheld or portable, machine mounted, benchtop or floor, and automatic or inline.  Micrometers may be supplied with plastic, heat insulating handles or holders.  The insulating handles help prevent measurement errors in the gage that could be caused by the heat from a human hand.  Machine travel enabled micrometers are typically mounted on a machine or are built into a product including machine tools, microscopes, and other instruments requiring precision dimensional measurement or position control.

 While similar to other gages in that they help to set and determine gauging standards, masters gages and setting gages are not used with other specific devices, instruments and sensors. Instead, masters gages and setting gages provide dimensional standards for calibrating other gages.  Masters gages and setting gages are designed to variety of tolerance grades in both metric and English dimensions. Gage blocks, end measuring rods, setting plugs, setting discs, setting rings, and thread standards are masters gages and setting gages that fit into this category.

Gage blocks provide fixed length, thickness, or angle standards and are manufactured to specific flatness, parallelism, and dimensional standards.  End measuring rods or micrometer standards are fixed length setting gage or standards used for checking or calibrating micrometers or other length / thickness gages.  End measuring rods consist of long, ground bars manufactured to precise tolerances, and with a central insulating handle.  Precision gage balls are precisely manufactured spherically shapes for gaging spherical cavities, tapered holes, or machine tool set up.

Setting rings, setting pins, setting discs and other setting gages are used to calibrate production functional gages for go / no-go assessment compared to specified tolerance.  Setting plugs are used for assessment of hole and slot dimensions or locations compared to specified tolerances.  Similarly, setting ring gages are used for assessment of the attributes of pins, shafts, or threaded studs.  Setting discs, also known as annular plugs, are large plug gages (over ~8" in diameter) use an annular disc design where the internal section is cut down to reduce weight and improve handling.  Setting discs have a similar design and are used to set or check micrometer or other OD gages.

Other types of masters gages and setting gages include master gage blocks, master or setting discs, and setting rings are types of master gages used to calibrate or set micrometers, comparators, or other gaging systems.  Working gages are used in the shop for dimensional inspection and periodically checked against a master gage.

 Magnifiers are inspection or assembly instruments that enlarge the image of a product or feature.  The level of magnification (generally less than 50X) differentiates magnifiers from their higher power cousins, microscopes.  Magnifiers are available in many configurations such as handheld, loupe, linen or folding, binocular, desktop, or headband styles. They are used in a wide variety of applications, including assembly, electronics manufacturing (PCBs), industrial inspection, precision machining, tool & die work, jewelry and gemology, medical and life sciences, textiles, vision or sight assistance, forensics, photography, and document analysis.

Magnifiers have various configurations and mountings available.  These include arm, boom and clamp, bar, rule and sheet, binocular, desktop stand, folding and linen, floor stand or mount, handheld, headband and visor, loupe, magnetic base, pocket, screen magnifier, and video and digital.  Arm, boom and clamp magnifiers are mounted on a rigid boom, flexible gooseneck, or articulating arm. This style of magnifier is used for inspection, jewelry work, assembly, or electronics manufacturing applications, where the ability to easily position the magnifier and provide two free hands is an asset.  Bar, rule, or sheet magnifiers are used to examine documents, photographs, or textiles.  They function by placing a plastic or glass lens on top of the item that is being examined.  Generally, hemispherical or Fresnel lenses are used in conjunction with these magnifiers.  Rule magnifiers have a scale printed or inscribed on a surface of the magnifier to allow for more precise measurements.  Binocular magnifiers are colloquially known as "headlights."  Folding and linen magnifier classification includes styles where the lens folds into the body for protection, or the lens or the body collapses to a more compact size for portability.  A variety of folding magnifiers are available, generally in handheld or desktop configurations.  Box-like folding magnifiers that mount on a desktop are often referred to as linen magnifiers.  Headband or visor magnifiers are worn on the head, like a hat or pair of glasses. Some varieties allow the user to flip lenses into and out of place to change the magnification level.  Loupes are commonly used by jewelers, a loupe is a small magnifier held in the eye socket to allow for intense scrutiny of an object.  Some styles are handheld or clip onto glasses.  Screen magnifiers are simply flat screens that are placed in front of a computer monitor, video or television screen, to magnify the image.  Video and digital instruments include all magnifiers that capture an image digitally though a video camera or CCD, and then electronically magnifying the image display on a screen.  The resolution of the initially captured image limits the level of magnification.

The most important specification of magnifiers is the magnification.  This is the number of times the image is magnified.  Common features of magnifiers include bifocal lenses, illumination, ESD safe, scale or comparator reticles, variable magnification, and work holders or manipulators.

Applications that use magnifiers include assembly, document and photograph inspection, electronics manufacturing, forensics, industrial inspection, jewelry and gemology, medical and life science, vision aid, tool and die or machinist, and textiles.