EML2322L / EML4502 Manufacturing Resources

This webpage outlines various cutting tools available in lab and tips for their selection and use. This condensed sheet lists each tool size stocked in the lab for quick reference. You are not limited to these tools; however tools not on this list must be purchased prior to manufacturing, as must tools for working with ferrous materials other than low carbon steels (e.g. AISI 1018, or other 1XXX series low carbon steels).  Each section includes links to common vendors to purchase tools not stocked in lab.

Table of Contents

Drills & Rapid Hole Making

Reamers & Precision Hole Making

Countersinks

Counterbores

Endmills

Taps, Dies & Threading
Damaged / Stripped Fastener Removal
Thread Repair

Cutting Tool Materials

Cutting Tool Coatings

Metrology

Drills & Rapid Hole Making [RETURN TO T.O.C.]

Basics of … Drills (Good Technical Info)

HSS Imperial Center Drills (sizes and lengths shown in table below)

CENTER DRILL BIT SIZES
Center Drill No.	Body Dia.	Drill Bit Dia.	Drill Bit Length
0	0.094	0.031	0.038
1	0.125	0.047	0.047
2	0.188	0.078	0.078
3	0.250	0.109	0.109
4	0.313	0.125	0.125
4½	0.375	0.141	0.406
5	0.438	0.188	0.188
6	0.500	0.219	0.219

HSS Jobber Drill Set Containing Fractional (1/64” – ½” by 1/64’s), Numbered (#1-#60), and Lettered (A-Z) Drill Sizes

Silver and Deming HSS Imperial Fractional Drills (9/16” – 1” by 1/64” increments, and 1-1/8” – 1-1/2” by 1/16” increments)

Metric HSS Jobber Drills (1 – 6mm in 0.1mm increments, 6 – 13mm in 0.5mm increments)

Taper Length (i.e. Long) HSS Drills (9/16” – 1” in 1/16” increments, 1-1/8” – 2” in 1/8” increments)

Extra-Long HSS Imperial Fractional Drills (1/8” – 1/2” in 1/64” increments)

Comparison of common drills from top to bottom: stub / screw machine length, jobber length, tapered length, extra-long (aircraft) length

HSS Flat Bottom Drills (1/64”-1” by 1/64 increments, and 1 1/8” – 1-1/2” by 1/16” increments)

Process Tip: Always use a regular tapered drill to create the hole and only use a flat bottom drill to finish it. In other words, NEVER try to drill the entire hole with a flat bottomed drill, as doing so is tremendously dangerous!

HSS Sheetmetal Drills (3/16”-1/2” by 1/64 increments

Process Tip: Always use these drills in drill press or milling machine, as they are very aggressive and can cause injury if used in a hand drill!

Imperial Tap and Drill Chart (Click for PDF Version) 

Imperial Tap and Drill Chart (Click for PDF Version) 

Drill Sizes Chart (Fractional, Lettered, Numbered, & Metric) (Click for PDF Version) 

Annular Hole Cutters (sizes 5/8” – 1-1/2” in 1/8” increments) and R8 Milling Machine Arbor.

Annular Hole Cutter In Use on Milling Machine (note the annular groove it cuts through the workpiece, giving the cutter its name)

Stepped Drill Bits for Creating Clearance Holes Thru Thin Materials (1/8” – 1-1/4” in 1/16” increments)

Reamers & Precision Hole Making [RETURN TO T.O.C.]

HSS Reamers: Fractional (sizes 1/16” – ¼” in 1/32” increments), Lettered (A – Z), and Numbered (#1 – #60)

HSS Reamers: Fractional Over and Under Sized (± 0.001” of the standard fractional sizes: 1/8” – 1/2” in 1/16” increments)

Reaming Tips Reference Document

Process Tip #1: When using reamers, leave 3% allowance for the reamer to remove. For example, if reaming a Ø ¼” bore, drill the hole to 0.250” – 3% ≈ Ø0.243” in preparation for reaming. The 1/64″ rule we use in lab works pretty well most of the time for the holes we make, but 3% is the standard.

Process Tip #2: Reamers typically perform best at one half the speed and twice the feedrate of the comparable size drill.

Process Tip #3: Although reamers are by definition finishing tools, ALWAYS use lubrication when using them in ANY material. WD-40 works well in aluminum.

Brazed Carbide Boring Bar Used on Lathe for Making a Precision Hole (± Ø0.0005”)

Brazed Carbide Boring Bar Assortment (for 0.375” and larger bores in ferrous + non-ferrous materials)

Indexable Carbide Boring Bar Used on Lathe for Making a Precision Bore (± Ø0.0005”)

Indexable Carbide Boring Bar Assortment (for 0.375” and larger bores in ferrous + non-ferrous materials)

Process Tip #1: When possible, drill the part to within a reasonable size prior to boring because drilling in a much more efficient (i.e. faster) process.

Process Tip #2: Indexable boring bar inserts have different sized corner radii. Larger corners are stronger and can take deeper depths of cut. Smaller corners are more fragile but produce better surface finish. The maximum depth of cut in our labs is twice the corner radius of the boring bar insert.

Countersinks [RETURN TO T.O.C.]

About Countersinks

Countersinks form a cone-shaped opening at the top of a hole, which acts as a seat for the head of a screw or rivet. They can also be used for chamferring, deburring, and creating openings for holding material between centers.

Flutes

Fast Cut — Have one flute and won't vibrate at high speeds. Also great for cutting smaller holes.

General Purpose — Have two, three, or four flutes. Tool life increases with more flutes because the cutting load is distributed over more edges. However, fewer flutes provide better chip clearance, which is a consideration when machining stringy materials like plastic.

Smooth Finish — Have six flutes. These remove more material per revolution and have a longer tool life than other countersinks.

Body Diameter and Countersink Angle

The countersink body diameter must be equal to or larger than the head diameter of the screw, center, or rivet being countersunk. Use a pilot hole that's larger than 10% of the countersink body diameter.

Countersinks of various angles are available for different purposes:

60° Countersink Angle: For holding workpieces between the centers on a lathe.
82° Countersink Angle: For flat- and oval-head inch screws.
90° Countersink Angle: For flat- and oval-head metric screws. They're also great for chamfering.
100° & 120° Countersink Angles: Primarily for rivets.

If ordering a countersink, a 90° countersink angle is likely the most versatile.

HSS Countsink Set (1/8” – 1” in size)

Counterbores [RETURN TO T.O.C.]

About Counterbores

Counterboring— Enlarge the top portion of an existing hole, forming a cylindrical-shaped opening with a flat bottom that acts as a seat for the head of a screw or wood plug.

Shallow Counterboring— Bore a shallow spot (1/8" or less) around a hole so that the head of the screw, bolt, or nut is slightly raised above the surface of the material (also known as spot facing).

Pilots— A pilot guides the counterbore as it penetrates the material, keeping it centered over the drilled screw hole and ensuring a level seat for the screw head. Counterbores with built-in pilots have a counterbore and pilot made from one piece of steel. Changeable-pilot counterbores have a removeable pilot, allowing you to use various pilot diameters in a single tool.

HSS Counterbores (for #6 – #10, ¼”, 5/16”, 3/8”, 7/16”, and ½” socket head cap screws)

HSS Counterbores (for M3 – M12 socket head cap screws)

An example of three counter bores for a socket head cap screw (left)

Endmills [RETURN TO T.O.C.]

Basics of … Endmills (Good Technical Info)

Endmill Nomenclature Figure 1 and Figure 2

Left to Right: Flat-Bottom, Bull-Nose (aka radius cutter), and Ball-Nose Endmills

Flat-Bottom (aka “Square”) HSS Roughing Endmills (sizes ¼” – 1” in 1/8” increments)

Flat-Bottom (aka “Square”) HSS Regular Endmills (sizes ¼” – 1” in 1/8” increments)

Ball-Nose HSS Endmills (1/8” – 1” in 1/8” increments)

Bull-Nose HSS Endmills (1/4” to ¾” in 1/8” increments, 0.015”, 0.030”, 0.060” corner radii)

HSS Milling Cutters (Left to Right: Dovetail cutter, woodruff cutter, 90° double-angle cutter)

Process Tip #1: Create a slot wider than the shank diameter of the cutter and as deep as the desired feature.

Process Tip #2: Use the spindle speed equal to that of a comparable size endmill.

Video illustrating use of Corner Rounding Endmills

Corner Rounding HSS Endmills (1/16” – ½” radius in 1/16” increments)

Taps & Dies & Threads [RETURN TO T.O.C.]

Basics of … Taps (Good Technical Info)

Types of Threads (Unified National, Whitworth, Buttress, etc.)

Tap Nomenclature

Cutting vs. Forming Taps

Straight vs. Spiral Flute Taps and Regular vs. Spiral Tip (aka Gun) Taps (1)

Straight vs. Spiral Flute Taps and Regular vs. Spiral Tip (aka Gun) Taps (2)

Pulley Taps and Extension Taps

Tap Extensions

STI (Screw Thread Insert) Taps

HSS Hand Taps & Dies (#4 to 1” taps & dies; M4 to M12 taps; M4 to M25 dies)

Common Types of taps: Taper Tap (for starting holes in hard materials), Plug Tap (for starting holes in easy-to-machine materials), and Bottom Taps (for cutting threads close to the bottom of blind (i.e. non-thru) holes)

Tapping Station for Creating Threads Perpendicular to Workpiece Surface

Spring Loaded Tap Guide for Creating Threads Co-Axial to Workpiece Centerline

National Pipe Threads (NPT) Male and Female Taps and Dies (sizes 1/8” to ¾”)

Thread Gages for Identifying Unknown Imperial or Metric Threads

Instructional Video on Identifying Thread Pitch and Size

Instructional Video on Measuring Thread Pitch Diameter Using Thread Wires

Damaged / Stripped Fastener Removal [RETURN TO T.O.C.]

Braddock Rule #8: Where there are fasteners and co-workers, there will one day be damaged fasteners! Unfortunately, history proves this statement correct, so good design engineers should know how to (1) not damage fasteners when using them and (2) how to repair fasteners damaged by others who didn’t know better. Read on if you want to be that fastener guru who impresses your bosses and coworkers with your fastener removal prowess J.

Before we talk about some common procedures and tools for removing damaged fasteners, let’s talk about how they get damaged in the first place; or better yet, how to NOT damage fasteners when using them.

The leading cause of fastener damage is ignorance regarding the proper tools for use installing and removing them. And with so many crappy tools and false marketing nonsense, it’s not surprising that most people are confused. So let’s discuss what we need to properly install and remove fasteners, as well as some things that may not be common knowledge:

1. Buy good quality tools. If you buy the cheap garbage at (gasp!) Walmart or Harbor Freight, you deserve to mess stuff up! If you want to not damage everything you work on, buy a quality set of screwdrivers, L-shaped hex wrenches, L-shaped torx wrenches, hex drivers, torx drivers, impact driver, and torque wrenches. Here is an excellent overview of common hand tools.

Yes, this will run anywhere from $500 - $1,000, so it’s not always feasible on a DIY-er budget, but rarely is the right way also the cheap way. Starting with screwdrivers, quality tools possess superior metallurgy, proper fastener engagement, and better ergonomics. Did you know they make screwdrivers with hex bolsters for use applying extra torque with a wrench; with striker plates and thru shafts for impacting with a hammer to break corroded fasteners loose; with laser etched tips to bite into the fastener head and reduce the cam-out effect; with superior ergonomics for everyday use; and with high grip handles for use in greasy or wet environments?

2. Hex and torx drivers are included on the previous list of required tools because it is not safe (for the user or the fastener!) to try and apply large amounts of torque to fasteners using hand-held wrenches. High torque results in high stresses. High stresses are resisted by higher strength materials. Higher strength materials are produced by heat treating (cheaper) or forging (more costly). And heat treating increases a material’s brittle nature. Could you imagine the danger in applying a large force through a brittle tool when it breaks? The user would most certainly be injured. Therefore, most hand-held hex and torx wrenches are not strong enough to apply the large loads needed to remove stuck fasteners, which is why we need to invest in quality metric and standard hex and torx drivers. In addition, hex and torx drivers are the only way to install these types of fasteners with a torque wrench, the use of which is imperative for proper installation!

3. Most people have not been taught hex wrenches are consumables and must be reground (“retipped”) or replaced at frequent intervals due to the incredibly high contact (Hertzian) stress applied to the corners of the tips when placed in simultaneous bending and torsion. The same applies for torx wrenches and drivers, except when these yield or wear, they must be replaced (unless you want more practice extracting damaged fasteners!).

Even screwdrivers need periodic replacement due to wear and yielding (albeit, the frequency is inversely proportional to the quality).

4. Know some fastener head types are inherently weaker designs. If you take a lot of things apart (an activity that teaches invaluable design and assembly skills!), you notice certain types of fasteners seem more susceptible to damage: button head hex, low head hex, flat head (countersunk) hex, slotted head screws, etc. In the case of button head, low head, and flat head hex fasteners, the broached hex is smaller and shallower than a regular hex head fastener of the same size, which makes the head MUCH more susceptible to yielding / stripping. In fact, when properly torqued, low and button head socket cap screws are so much weaker in this regard, it’s standard practice in precision machine assembly to never reuse them!

5. Know some fastener head types are inherently easier to mix up, with disastrous results; for example, torx vs. hex, and torx vs. torx PLUS!

6. Never, EVER, use a ball-end hex wrench to tighten or loosen a fastener. The ball end allows convenience off-axis access to rotate the fastener, but high torque should never be applied using one, because of the greatly reduced contact area between the major diameter of the ball and the broached hex in the fastener head.

7. Understand cam-out and how to mitigate it. Cam-out refers to the axial component of the reaction force created when you try to torque a fastener. Stated another way, when using a traditional screwdriver with a slotted or phillips head, the more torque you apply, the higher the axial force becomes which tries to disengage the screwdriver from the screw. There are many modern developments in screw drives to reduce this cam-out phenomena, but it will likely continue to exist in many of the fasteners you deal with in industry. The takeaway here is to apply as much axial force as possible anytime you are applying a high amount of torque to a phillips or slotted style fastener. The impact driver discussed in detail below leverages this understanding of cam-out physics for its benefit.

8. Take time to prepare hex head screws for removal. During use it’s common for debris to pack inside the broached hex recess in the fastener head. If you don’t take time to remove that debris with a pick, the hex wrench will not engage as much of the broached hex as possible, greatly increasing the chance of stripping the head.

9. When taking apart fasteners you believe may be corroded or really stuck in place, ALWAYS take the time to use an impact driver to shock the fasteners and break them loose. Be careful, however, as these tools are SO EFFECTIVE they will shear the head of a fastener right off if you set them to rotate the wrong direction! Click the previous hyperlink a short application video.

10. Always remember Side’s Rule #1: Your first shot’s your best shot! Applied to fasteners, put everything you learned above into action the next time you’re asked to install or remove stubborn fasteners. It only takes a little longer to do the things that are going to GREATLY improve your chance of removing a stuck fasteners, versus spending ten times longer trying to fix a fastener whose head you stripped.

Now let’s talk about some common procedures and tools for removing damaged fasteners:

1. Often an impact driver can be used to salvage the head of the fastener and break it loose at the same time.

2. Often applying heat with an oxy-acetylene torch will cause the corroded fastener joint to expand and contract enough (especially when used in conjunction with a quality penetrating lubricant like PB Blaster®), to cause the fastener to loosen. This obviously only works on components that a little heat won’t damage.

3. If dealing with stripped hex head fasteners, you have some good options.

The cheapest option is to make sure the broached hex is clean and the driver / wrench is in pristine condition (if not, simple retip the wrench by grinding a bit off the end). Next, you can try to file or grind a slight taper on the next larger size wrench (std. or metric, don’t be afraid to mix in this instance; use the size differential to your advantage), and hammer the driver into the damaged hex. If using this option, employ a large enough hammer to apply sharp impacts to the fastener head, which will help loosen the threads (like an impact driver). In a pinch, you can also try driving a quality (high strength) torx bit into what remains of the hex head, but this is usually akin to a Hail Mary late in the game J.

Sock It Out, Inc. makes a commercial version of these tapered removal tools (for standard and metric hex head fasteners as well as torx) that make quick work out of removing stripped hex fasteners (both cap screws and set screws) and torx fasteners.

4. If dealing with fasteners that have sheared, or the head is simply not salvageable, you have far too many options with which to waste your time, so let me show you the two that commonly work J :

First, are the ubiquitous spiral flute screw extractors, commonly called Easy-Outs. However, don’t let the name mislead you, as the only thing easy about using them is snapping them off inside the broken fastener you’re trying to remove! When using these (or any) extractors, it’s imperative you drill an appropriately sized pilot hole through the CENTER of the damaged fastener. The further the hole is off center, the more likely the extractor is the break.

The second style works similar to the first, however, instead of a reverse spiral, they are simply tapered square punches which are driven into the pilot hole to lock into the damaged faster shank and allow reverse torque to be applied. The spiral flute extractors generally work the best, with the exception of left-hand threads.

Thread Repair [RETURN TO T.O.C.]

Corollary to Braddock Rule #8: Where there are threads and co-workers, there will one day be damaged threads! Unfortunately, history also proves this statement correct, so good design engineers should know how to repair damaged threads. Read on if you want to be that fastener guru who impresses your bosses and coworkers with your thread repairing prowess J.

1. Make sure whoever you are trying to help with the repair understands you are not responsible if it doesn’t work out. Far too often a co-worker will try to fix their mistake before asking for help, and their attempted fix makes your attempt at repair more challenging! In addition, some co-workers are happy to let you share the blame for the damaged thread once you lay your hands on it, so never try to help a co-worker you know is unprincipled.

2. Verify the correct thread spec. Despite what anyone tells you, it’s always good for verify the thread size yourself. If there are similar features on the part, simply check another fastener, or gage another threaded hole.

3. Use a roll / form tap to try and salvage internal threads by reforming them back to the original profile. Using a cut tap will further damage the thread, so don’t try it.

4. If the roll / form tap doesn’t fix the problem, and the threads are deep enough in the part, you can sometimes drill out the damaged threads and use a longer fastener which can engage more of the deeper, (hopefully!) undamaged threads.

5. If the threads can’t be salvaged, it’s typically time to consider use of a threaded repair insert. There are a few quality styles on the market: EZ-LOKs, Helicoils, Keenserts, and Timeserts. Each work well in the proper application and each have their drawbacks, as shown in these two good product comparisons: one and two.

Note it’s worth your time to research all of these insert types, because they aren’t just used to fix damaged threads, but also in many applications where higher surface hardness, lower contact stress, and higher fatigue resistance are needed when placing thread in non-ferrous materials. Helicoils require special STI (Screw Thread Insert) taps, but are used widely in aerospace applications (perhaps too widely and for legacy reasons J ?). EZ-LOKs are available in thin and thick wall versions, which provide more options.

Cutting Tool Materials [RETURN TO T.O.C.]

The primary rule when selecting the proper cutting tool is that the tool material must be harder/stronger than the workpiece being cut, or the tool will be damaged by the material. On the other hand, the stronger the tool material, the more brittle and expensive the cutting tool. Therefore, much like selecting workpiece materials, cutting tool materials should be selected so they are harder/stronger than the workpiece being cut, but not unnecessarily so.

There are five categories of common cutting tool materials: high speed steel (HSS), cast alloys (e.g. Stellite, Tantung, etc.), tungsten carbides, ceramics, and cermets (ceramic metals). Conveniently, high speed steel (HSS) and tungsten carbide (WC) tools comprise over 90% of the modern cutting tool market, so our discussion will focus on these two materials.

HSS is the acronym for the most common grade of alloy steel used in the manufacture of cutting tools. HSS offers good hot hardness, which refers to its ability to maintain a sharp cutting edge as the cutting tool elevates in temperature during the machining process. Cobalt can be added to the HSS alloy mix to provide enhanced hot hardness. HSS also possesses high toughness, which is the ability of the material to absorb a significant amount of energy before fracturing. For reference, the yield strength of HSS is around 45,000 psi. Common cutting tools made from HSS include drill bits and reamers, endmills, taps and dies, bandsaw and hacksaw blades, and lathe turning and facing tools.

WC is the abbreviation for tungsten carbide, which is manufactured by sintering (baking) tungsten carbide powder with binders and other additives to form solid carbide shapes which are often ground to final shape. WC has similar properties to ceramic: it can withstand extremely high temperatures and has a high compressive strength (450,000 psi), but it is very brittle. WC tools can typically cut workpiece materials at 2.5 times the speed of HSS, and they typically cost 2 to 5 times as much.

Comparison of Hardness & Wear Resistance vs. Strength & Toughness of Common Cutting Tool Materials

Additional information on Cutting Tool Materials

Cutting Tool Coatings [RETURN TO T.O.C.]

Several coatings are available for cutting tools for the purposes of providing high temperature thermal barriers and reducing the friction coefficients between the cutting tool and workpiece materials. Since heat is the limiting factor for how fast a particular tool can rotate when cutting a particular material, tool coatings permit 15-30% higher cutting speeds, while adding about 10% to the cost of the tool. Common coatings include black oxide, titanium nitride (TiN), aluminum titanium nitride (AlTiN), titanium carbonitride (TiCN), and zirconium nitride (ZrN).

Coatings are generally not useful when tools are used on manual machines because of the lower spindle speeds and the fact that most tools will be damaged in use by accidentally feeding them too aggressively as opposed to developing dull edges due to extensive use.

Common Cutting Tool Coatings Applied to Finishing and Roughing Endmills

Harvey Tool’s Excellent Tool Coatings Chart

Visual Tool Coatings Chart

Metrology [RETURN TO T.O.C.]

10:1 Rule – The resolution of the measuring instrument should be ten times greater than the feature to be measured. For example, if the length of a part is specified with a 0.005” tolerance, it must be measured with an instrument with a resolution 0.0005″.

An excellent quick guide to understanding errors in hand-held measuring instruments can be found here

A comprehensive guide to precision measuring instruments can be found here

Standards

Standards are objects that have been certified by NIST to meet certain dimensional accuracy targets. They are used as a reference for the calibration of measuring equipment such as calipers, micrometers, and dial indicators. There are several grades available: reference (AAA), calibration (AA), inspection (A), and workshop (B). Since metals expand at a rate of approximately 0.000010″/°F, all certification measurements occur at a standardized 68°F (20°C).

Gauge Block Set (accurate to ±0.000050″; blocks can be joined with very little dimensional uncertainty)

Gauge Pin Set (accurate to ±0.000050″; may also be used to determine the size of a hole to ±0.001″)

Micrometer Standards (for setting the zero point of outside micrometers; 1″ standard accurate to ±0.000050″; 5″ standard accurate to ±0.00015″)

Outside Measurements

6″ Dial Calipers can measure outside, inside, depth, and shoulder measurements

· Accurate to ±0.001″ / ″ of travel; this error compounds linearly (i.e. a 6″ measurement taken with it is only accurate to ±0.001″)

· Prone to Abbe error, which says that a source of error is introduced anytime the reference line of a measuring system doesn’t lie along the same line as the dimension being measured

· Prone to parallax error, where the observed measurement changes depending on the viewing angle

· The ID measuring jaws are offset from one another, which means the jaws will never “find” the maximum diameter of the workpiece

· No way to limit applied pressure, resulting in a lack of repeatability and reproducibility

· Can improve accuracy by calibrating with a standard that is close to the size being measured

6” Digital Calipers

· accurate to ±0.001″ over the entire 6″ range of travel

· still prone to each of the errors listed above, excluding parallax error

OD Micrometers

· accurate to ±0.000050″

· according to 10:1 rule, can measure features to ±0.0005″

· spindle has a torque limiting ratchet or clutch to improve repeatability and reproducibility

Set of 1-6″ OD Micrometers

· each micrometer has a range of 1 inch

· set includes 0-1″, 1-2″, 2-3″, 3-4″, 4-5″, 5-6″ micrometers

· limiting the travel of the spindle results in a more accurate measurement

· any quality micrometer will come with a standard that can be used to zero the micrometer

Micrometer Stand (used to hold micrometers to minimize heat input from the user and hold the micrometer steady when measuring)

Inside Measurements

ID Micrometers (accurate to ±0.0003″)

Dial Bore Gauge (the dial indicator is zeroed at the desired measurement using a micrometer, and the relative displacement is used to determine bore size)

Telescoping Bore Gauge (the gauge has two spring loaded cylinders that are pushed into contact with the interior of the bore and a locking mechanism to retain the bore size once removed. A micrometer is then used to measure the bore gauge.)

Relative Measurements

Dial Indicator (accurate to ±0.001 - 0.0002″ depending on indicator; shown above measuring the straightness of a vise jaw)

Drop Indicator (accurate to ±0.001 - 0.0001″ depending on indicator; shown above measuring the concentricity of a part in a lathe chuck)

Other

Depth Micrometer (accurate to ±0.0001″ for the micrometer head, varies per measuring rod length)

Thread Pitch Gauge (used to determine thread pitch)

Radius Gauge (used to determine the size of internal/external radii)

Feeler Gauge (used to determine thickness, usually of a gap)

Electronic Measurement

Coordinate Measuring Machine (accuracy up to ±0.000015″; measurements are made with a probe mounted on a multi-axis head)

Laser Scanning (creates a point cloud of an object, high-end sensors can have a point spacing of as small as 0.001″)

White Light Interferometry (non-contact method for measuring surface profiles to ±0.000005″)

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Photo copyright notice: many of the photos and content on this page are taken from Micro-Machine Shop, which does an excellent job organizing and presenting it.