Beginner’s Guide to Blueprint Reading

Learning to read blueprints can be hard. That’s why we’ve broken down the process into bite size chunks. All of the basic components of an engineering drawing are detailed below with links throughout to give you more info on each subject.

Use the table of contents below to jump straight to your topic of choice and if you don’t find what you are looking for please leave a comment at the bottom and we will tackle any blueprint related questions we may have missed.

Components of a drawing

Title block

title block example
Title block example

A blueprint title block contains the high-level identification information. The title block of a blueprint can vary quite a bit across different companies. In general, the title block can be found in the bottom right of the blueprint and will include the following:

  1. Drawing or part number and revision
  2. Part name
  3. Company name
  4. 1st or 3rd angle projection
  5. Scale

Tolerance block

tolerance block example
Tolerance block example

The tolerance block, sometimes referred to as the general tolerance block, is usually located in the bottom right or bottom middle section of the blueprint. The tolerance block identifies the tolerances associated with dimensions that are not directly listed on the drawing.

This can include items such as the blueprint dimensional units (imperial or metric) or surface roughness requirements.

Units of measurement

The units of the print are very important because there is a huge difference between 25.4mm and 25.4 inches. The measurement units will often be called out in the title block or tolerance block but occasionally will be in another section of the blueprint such as in the notes.

Angular units are important also but there is usually less confusion associated with them because decimal degrees and degrees, minutes, seconds are so different.

Types of projections

Projections are different ways of representing parts on a blueprint. Basically this means there are different methods of showing the same part.

1st angle projection, sometimes referred to as the European convention, is a method of displaying the various views of the part as if the part has been flipped to each side.

Notice how the car is flipped below in each view of a 1st angle projection blueprint.

1st angle projection car example
1st angle projection example - click to enlarge

3rd angle projection, the American convention, is a method of displaying the various views of the part as if the part is placed in a bowl and rolled in the bowl to the other views.

Notice how the car is flipped below in each view of a 3rd angle projection blueprint.

3rd angle projection example - click to enlarge

Projections can be hard to describe in words. Just remember that 1st angle projections are a flop method and 3rd angle projection is a roll method. 

Types of tolerances

There are multiple ways of tolerancing a dimension. Below are the ways of directly dimensioning a feature with standard tolerances. GD&T tolerances are a separate topic altogether.

Limit tolerances

limit tolerance example
Limit tolerance example

Limit tolerances list a range that the dimension must fall within. No calculation needed. Simply keep it between the numbers.

Unilateral tolerances

unilateral tolerance blueprint example
Unilateral tolerance example

Unilateral tolerances are given when the allowable variation is in a single direction such as the example below. In this example, the part cannot have a diameter that is over 6mm.

Bilateral tolerances

bilateral tolerance blueprint example
Bilateral tolerance example

Bilateral tolerances, often referred to as plus or minus tolerances, have a nominal size and a tolerance in the positive and negative directions. Often this tolerance will be equal in both directions, but it doesn’t have to be. Sometimes you will see bilateral tolerances that allow more variation in one direction.

Notes section

Notes on a blueprint can have a huge impact on the component requirements. The notes are often where surface treatment requirements such as heat treating, anodizing and other similar requirements are documented.

Literally anything can be listed in the notes section and the items listed can have a large bearing on the complexity of the part.

Pay attention to your notes section, there are often critically important features and characteristics relative to the part listed.

Symbols

A wide range of symbols are used to create engineering drawings. There are also specialty blueprint symbols associated with items such as welding or electronic components, but I will only be covering the standard blueprint symbols including those related to geometric dimensioning and tolerancing (GD&T).

Center lines

Center lines, such as the center of a thru hole are depicted on a drawing with long and short lines spaced alternately.

In the example below, the centerlines are shown as blue lines.

hidden and center line blueprint example
Center lines and hidden lines example

Hidden lines

To show features in a blueprint view that would not actually be visible, hidden lines are used. These hidden lines are show on a drawing as lines made of dashes.

In the example above, the hidden lines are shown as red lines

Diameters

Diameter Blueprint GD&T Symbol o with line through it
Diameter symbol

Diameters are round or cylindrical features. Features such as the outside diameter of a part and the size of a hole or counterbore are examples of diameters. They will be referenced using the diameter symbol shown below.

Countersinks

Countersink Blueprint GD&T Symbol two lines pointing down
Countersink symbol

Countersinks are a chamfer on a hole that allows a fastener such as a screw to sit flush or below the part surface. The blueprint symbol for a countersink is shown below.

countersink blueprint example
Countersink callout example

Counterbores

Counterbore Blueprint GD&T Symbol u shape
Counterbore symbol

A counterbore is a circular hole that is deep enough to allow the head of a fastener to be recessed. Counterbores will be shown on a blueprint with a diameter and depth symbol associated with them.

counterbore blueprint example
Counterbore callout example

Radii

Radius callout example

Radii show up on prints for many different reasons. The most common application of a radius is to specify the maximum radius allowed in the bottom of a slot or hole. They are frequently used as a form of edge relief similar to a chamfer. While these are the most common radius uses, radii can be dimensioned for all kinds of internal and external features.

When a radius smoothly blends into a surface, it will occasionally be called out as a full radius or full R. A full R callout does not change the way a radius is measured or add any additional requirements.

Holes

thru hole blueprint example
Hole callout example

Holes are about as simple as they come. They come in two varieties, thru holes and blind holes. When shown on a drawing they will usually be referenced by their size and location to the center of the hole.

Datums

Datum Blueprint GD&T Symbol a in a box with arrow
Datum symbol

Datums are reference points for measurements and are utilized in many GD&T callouts. You will find datums shown on a drawing to identify the feature as a datum or as part of a GD&T callout in a feature control frame.

GD&T Symbols

gd&t symbols
gd&t symbols

Basic dimensions

Basic Dimension Blueprint GD&T Symbol dimension in a box
Basic dimension example

Basic dimensions are the theoretically perfect size or location of a part feature. The variation from this “perfect” size or location will be used to measure another characteristic of the part such as true position or profile. Basic dimensions do not have a tolerance themselves and instead are controlled by another GD&T callout.

Reference dimensions

Reference Dimension Blueprint GD&T Symbol dimension in parentheses
Reference dimension example

Reference dimensions are just what they sound like. They are placed on a print for reference only. They have no requirements associated with them and no tolerances either. They generally get used in one of two ways, they will be used to highlight something that might not be immediately clear without the reference dimension listed or they will be used to show the approximate dimension in another unit system (metric vs imperial units).

Chamfers

chamfer callout blueprint example
Chamfer callout example

Chamfers are used to remove the sharp edges of a part. This provides safety for both the part and the person using the part. Chamfers are frequently specified in many different places. They can be listed directly on the part, in the notes section or in the general tolerance block.

When the chamfers are small, at times they will be listed as a break edge.

Spotfaces

spotface example on mechanical blueprint drawing
Spotface callout example

Spotfaces are a small counterbore that is machined so that a fastener can sit flat on the part. They are essentially just shallow counterbores and will be dimensioned as such.

Bolt hole circles

basic dimensions for a bolt hole circle
Bolt hole circle callout example

A bolt hole circle will be shown on a print using multiple dimensions. This will include the size of the individual holes, the angle between the center of the bolt hole circle and the individual holes along with the size of the bolt hole circle itself.

Knurling

knurling blueprint callout examples
Knurling callout examples

Knurling is a textured pattern on a part. It is added for visual appeal or added grip. Knurls will be called out by the pitch, diameter, and type of knurling.

Surface finish/surface roughness

Surface Finish Blueprint GD&T Symbol check mark
Surface finish/roughness symbol

The surface finish quality is specified with the use of a check mark on the surface. The number above the start of the check is the required surface finish. If there are two numbers present, the surface roughness must fall within the range specified. If only one number is specified, the surface roughness must be less than or equal to the specified value.

Surface finish requirements are frequently specified directly on the applicable surfaces as well as in the notes section and general tolerance block.

Threads

Threads will be specified in either the ISO metric format or Unified National Coarse (UNC) thread format. This article clarifies the details of thread callouts.

Want to learn more?

GD&T is a complicated subject and understanding it correctly can be the difference between a perfect part and scrap.

The best way to learn GD&T is from experienced teachers who can break down the material into manageable pieces.

Luckily, we know someone.

And MachinistGuides.com readers get an exclusive discount on training!

Related articles

Geometric Dimensioning and Tolerancing Font – GD&T Keyboard Shortcuts

How to insert symbols into a Microsoft Word document

To insert GD&T symbols into Word, take note of the codes in the table below.

There are two types of symbols below. Some are alt codes (ALT+248) and some are Unicode characters (25B1 then ALT+X). Alt codes are entered by holding the ALT key and pressing the number code. Unicode characters are entered by typing the code and then holding the ALT key and pressing X.

How to insert GD&T symbols into a Microsoft Excel document

Not all the codes work in Excel. The ALT codes (ALT+248 style) work but the Unicode characters (25B1 then ALT+X style) do not. The best way to insert the GD&T symbols into Excel is to copy and paste the symbols.

GD&T Symbols Alt Codes

Symbol Name

Symbol

Code

Straightness

ALT+22

Flatness

25B1 - ALT+X

Circularity

25EF – ALT+X

Cylindricity

232D – ALT+X

Profile of a Line

ALT+239

Profile of a Surface

2313 – ALT+X

Angularity

2220 – ALT+X

Perpendicularity

ALT+8869

Parallelism

//

2225 – ALT+X

True Position

2316 – ALT+X

Concentricity

ALT + 10686

Symmetry

232F – ALT+X

Circular Runout

↗

2197 – ALT+X

Total Runout

2330 – ALT+X

Free state

ALT + 9403

Least material condition

ALT + 9409

Maximum material condition

Ⓜ

ALT + 9410

Projected tolerance zone

ALT + 9413

Regardless of feature size (RFS)

ALT + 9416

Tangent plane

ALT + 9417

Unequally disposed tolerance

ALT + 9418

Common Blueprint Symbol Alt Codes

Symbol Name

Symbol

Code

Degree

°

ALT + 248

Plus or Minus

±

ALT+241

Diameter

Ø

ALT+0216

Depth

ALT + 8615

Greater Than or Equal To

ALT+242

Less Than or Equal To

ALT+243

Counterbore

ALT+9012

Countersink

ALT+9013

Micro

µ

ALT+230

Surface Finish

2713 - ALT+X

Centerline

ALT + 8452

Want to learn more about GD&T?

GD&T is a complicated subject and understanding it correctly can be the difference between a perfect part and scrap.

The best way to learn GD&T is from experienced teachers who can break down the material into manageable pieces.

Luckily, we know someone.

And MachinistGuides.com readers get an exclusive discount on training!

Bilateral Tolerance Guide [Examples & Explanation]

What is a bilateral tolerance?

A bilateral tolerance is a plus or minus tolerance (+/-). It allows variation from the nominal size in both a positive and negative direction. 

In most cases, the bilateral tolerance will be specified as equal in both directions such as 10.0mm +/- 0.5mm.

This is not always the case though and a bilateral tolerance does not need to have equal positive and negative tolerances. 10.0mm +0.2mm/-0.3mm would be an acceptable bilateral tolerance as well.

Here are some quick bilateral tolerance examples:

  • 5.5″ +/- 0.25″
  • 5.5″ +1.0″/-0.5″
  • 25.5mm +0.1mm/-0.2mm
  • 30.6mm +/- 0.3mm

Notice that in each of the examples there is allowed variation (tolerance) from the nominal size in both directions.

A tolerance of 25.5mm +0/-0.2mm would not be a bilateral tolerance because it has no tolerance in the positive direction. This would be an example of a unilateral tolerance.

Bilateral tolerance symbol

There is no GD&T symbol for a bilateral tolerance.

Per ASME Y14.5, the notation for a bilateral tolerance is to show a plus and a minus tolerance associated with a nominal dimension and neither of them is a zero.

Want to learn how to type GD&T symbols with no special fonts needed?

How to read a bilateral tolerance

Let’s start with our examples from above

  • 5.5″ +/- 0.25″
  • 5.5″ +1.0″/-0.5″
  • 25.5mm +0.1mm/-0.2mm
  • 30.6mm +/- 0.3mm

Now let’s break it down so you can see what the nominal size is as well as the top and bottom ends of the tolerance zone.

Nominal Size

Bottom of Tolerance

Top of Tolerance

5.5"

5.25"

5.75"

5.5"

5.0"

6.5"

25.5mm

25.3mm

25.6mm

30.6mm

30.3mm

30.9mm

Bilateral tolerance examples

Types of bilateral tolerances

Equal bilateral tolerance

bilateral tolerance blueprint example
An example of an equal bilateral tolerance

An equal bilateral tolerance will have equal plus and minus tolerances such as 6.35 +/- 0.025 as shown in the example above. 

Unequal bilateral tolerance

An example of an unequal bilateral tolerance

An unequal bilateral tolerance will have plus and minus tolerances that are not the same and neither is zero such as 17.0 +0.1/-0.2 as shown in the example above.

Bilateral tolerances compared to other tolerance types

Bilateral tolerance vs unilateral tolerance

A bilateral tolerance allows a tolerance in both directions.

A unilateral tolerance allows a tolerance in only one direction.

A bilateral tolerance is plus AND minus tolerance. A unilateral tolerance is a plus OR minus tolerance.

Here are some examples of unilateral tolerances:

  • 10.0mm +0/+0.5mm
  • 5.515″ +0.010″/+0.015″
  • 2.325″ +0/-0.005″
  • 4.5mm -0.2/-0.3mm

Bilateral tolerance vs limit tolerance

A bilateral tolerance specifies a nominal size and a plus/minus tolerance. These values are used to determine the tolerance range for a feature.

A limit tolerance skips the calculation step and simply gives you the tolerance range.

The table below shows bilateral tolerances with their equivalent limit tolerances.

Bilateral Tolerance

Limit Tolerance

10.0 +/-0.5

9.5 - 10.5

5.525 +0.025/-0.050

5.475 - 5.550

7.55 +/+0.15

7.40 - 7.70

2.324 +0.005/-0.010

2.314 - 2.329

Want to learn more?

GD&T is a complicated subject and understanding it correctly can be the difference between a perfect part and scrap.

The best way to learn GD&T is from experienced teachers who can break down the material into manageable pieces.

Luckily, we know someone.

And MachinistGuides.com readers get an exclusive discount on training!

Related articles

Unilateral Tolerance Guide [Examples & Explanation]

What is a unilateral tolerance?

Basically, a unilateral tolerance is a type of tolerance that is only allowed in one direction. Either an all plus tolerance or an all minus tolerance.

Here are some quick unilateral tolerance examples:

  • 10.0mm +0/+0.5mm
  • 5.515″ +0.010″/+0.015″
  • 2.325″ +0/-0.005″
  • 4.5mm -0.2/-0.3mm

Notice that in these examples, all of the allowed size variation is in one direction. The direction can be positive or negative and zero is allowed.

Unilateral tolerances are often used to specify dimensions that require a specific fit with a mating part.

unilateral tolerance blueprint example
Unilateral tolerance shown on a blueprint

Unilateral tolerance symbol

There is no GD&T symbol for a unilateral tolerance.

Per ASME Y14.5, the notation for a unilateral tolerance is to show a plus or a minus tolerance associated with a nominal dimension. It is acceptable for one of the specified tolerances to be zero.

Want to learn how to type GD&T symbols with no special fonts needed?

How to read a unilateral tolerance

Let’s start with our examples from above. 

  • 10.0mm +0/+0.5mm
  • 5.515″ +0.010″/+0.015″
  • 2.325″ +0/-0.005″
  • 4.5mm -0.2/-0.3mm

Now let’s break it down so you can see what the nominal size is as well as the top and bottom ends of the tolerance zone.

Nominal Size

Bottom of Tolerance

Top of Tolerance

10.0mm

10.0mm

10.5mm

5.515"

5.525"

5.530"

2.325"

2.320"

2.325"

4.5mm

4.2mm

4.3mm

Regardless of what the nominal size is, the requirement for each of these unilateral tolerance examples would be that the dimension must fall within the top and bottom tolerance range. 

Unilateral tolerances compared to other tolerance types

Unilateral tolerance vs bilateral tolerance

unilateral tolerance blueprint example
A unilateral tolerance example

A bilateral tolerance allows a tolerance in both directions.

A unilateral tolerance allows a tolerance in only one direction.

A bilateral tolerance is plus AND minus. A unilateral tolerance is a plus OR minus tolerance.

If we take the unilateral tolerance from the picture above and convert it to a bilateral tolerance it could be either:

  • 39.75 +/- 0.25
  • 39.7 +0.3/-0.2
  • 39.6 +0.4/-0.1

Notice that the important feature of the tolerance is that it has both a positive and negative tolerance. Neither side of the tolerance is zero.

Unilateral tolerance vs limit tolerance

A unilateral tolerance specifies a nominal size and a plus or minus tolerance. These values are used to determine the tolerance range for a feature.

A limit tolerance skips the calculation step and simply gives you the tolerance range. Instead of a nominal size and a tolerance, the top and bottom of the tolerance range are directly listed.

Let’s compare some unilateral and limit tolerances to see how they differ:

Unilateral Tolerance

Limit Tolerance

10.0 +0/-0.5

9.5 - 10.0

5.525 +0.025/+0.050

5.550 - 5.575

7.55 +0/+0.15

7.55 - 7.70

2.324 -0.005/-0.010

2.314 - 2.319

What is a unilateral tolerance used for?

A unilateral tolerance is most often used to specify a tolerance associated with a specific fit such as a clearance fit or interference fit.

Want to learn more?

GD&T is a complicated subject and understanding it correctly can be the difference between a perfect part and scrap.

The best way to learn GD&T is from experienced teachers who can break down the material into manageable pieces.

Luckily, we know someone.

And MachinistGuides.com readers get an exclusive discount on training!

Related articles

Break Edge – All About

What is a break edge?

break edge blueprint examples

A break edge means the removal of material, usually in the form of a chamfer or radius to remove the sharp edge.

Machining a surface will often leave a corner which can be dangerous for both the part and the part handler. Many times there will be a burr (raised piece of material), left on the edge which can be razor sharp. Using a deburring tool can break the edge to remove the sharp 

A broken edge is usually specified as a maximum value or with no value at all. If no value is specified, the break edge has not been constrained sufficiently.

A break edge callout with no maximum size referenced would normally be assumed to be approximately .005-.010” though in some instances it could be larger.

What does a break edge look like?

Break edge on a physical part

In the brass cube below, notice how the corners have all the sharp edges removed. This is an example of a break edge.

metal cube with break edge

Break edge on a blueprint

Break edge symbol

There is no GD&T symbol for a break edge. Break edges are also not referenced in the engineering drawing standard ASME Y14.5.

Break edge callouts are specified directly on the drawing to reference a certain surface or as a note e.g. “Break all sharp edges”.

At times, the break edge specification may be contained in the general tolerance block such as shown below.

Break edge note example

general break edge note on blueprint
Break edge note example

How to make a break edge

Break edge on wood

Using 180 grit fine sandpaper is the easiest way to create a break edge on a wooden workpiece. This can also be used together with a block plane to chamfer the edge and then soften it with a light sanding.

Break edge on metal

Because metal tends to be more durable, you have more choices for creating a break edge on your piece of metal.

You can use:

  • A chamfer deburring tool which is a specialty tool designed to remove burrs from the edges of parts
  • A file to knock the edge off a part
  • Sandpaper
  • A grinding wheel
  • A rotary tool such as a Dremel

Break edge on glass

To create a break edge on a piece of glass, use one of the following:

  • Diamond file
  • Grinding wheel
  • Rotary tool with diamond wheel

How to measure a break edge

Which measuring tools to use

igaging pocket comparator with reticles and case
A pocket comparator with various reticles for measuring

The size of a break edge is measured the same as a standard chamfer or radius. If a measurement is required, a pocket comparator or eye loupe with a reticle are the most common inspection tools to use. 

An optical comparator with or without an overlay could also be used. See the examples below to better understand how the size of a break edge would be determined.

How to measure the break edge based on your blueprint

break edge examples

On the left is a chamfered break edge. The size is measured from the left edge of the part to the intersection of the break edge and the top of the part. This is done in both the x and y directions (up and down, left and right). 

On the right is a break edge created by a radius. The same measurement technique applies with the exception that the intersection would now be called the tangent point or point where the radius meets the straight edge.

Break edge compared to similar features

Break edge vs chamfer

The difference between a break edge dimension and a chamfer dimension is generally in the tolerancing of the two. A chamfer is usually thought of as being toleranced in a way that places tighter constraints on the feature. 

Often a chamfer callout will have a tolerance associated with the angle and a break edge will not.

Break edge vs radius

A break edge can be a radius. Many times, the person or company machining the part will round the edge using a variety of techniques including tumbling, specialty tools or even sandpaper.

Want to learn more?

GD&T is a complicated subject and understanding it correctly can be the difference between a perfect part and scrap.

The best way to learn GD&T is from experienced teachers who can break down the material into manageable pieces.

Luckily, we know someone.

And MachinistGuides.com readers get an exclusive discount on training!

Chamfer and Chamfering Guide [Learn Quick]

What is a chamfer?

a picture of a chamfered part
A chamfered corner

A chamfer is an angle on the edge of a workpiece.

They are created for mainly for protecting the chamfered object as well as anyone who might come in contact with the object.

The edge can be the outside of the part, where a hole breaks through a surface or where any two surfaces meet. 

Notice the chamfered edges in the picture above.

chamfered cube

The cube above has chamfered corners where all the main faces intersect.

Chamfering those intersections reduces the sharpness of, or softens the corners. 

Types of chamfers

Leg length chamfers

The most common way to spec a chamfer is by giving its leg length size and the chamfer angle.

In the picture of a triangle below, the legs are the a and b sides of the triangle.

right triangle with sides and angles identified

If no angle is given, the chamfer angle would be assumed to be 45 degrees. This can be a dangerous assumption though. It is always best to confirm the chamfer angle when not directly specified.

Face width chamfers

Occasionally, a chamfer will be specified as being measured as a face width. This can be seen abbreviated as F.W. on some blueprints. 

In the picture below, the leg length of the chamfer would be the length of the a and b sides. These would be equal in a 45 degree chamfer. The length of the c side would be the face width of the chamfer. 

right triangle with sides and angles identified

If a chamfer is called out as a face width, then it is to be measured along the hypotenuse of the chamfer. 

To convert a leg length dimension to face width simply multiply the leg length value by 1.414. To convert from a face width dimension to a leg length dimension, reverse the process and divide by 1.414. 

It should be noted that these conversion factors only work if the chamfer is at 45 degrees (the most common chamfer angle). If you need to calculate the face width of a chamfer at a different angle use a triangle calculator.

Chamfers compared to similar features

Chamfer vs bevel

A chamfer and a bevel are the same, especially in the case of machining.

Some will debate this point and argue that a chamfer takes the sharp corner off the part and that a bevel would do the same but all the way to the opposite side surface.

While there are some diagrams available online that will show this as true, this is incorrect. Merriam-Webster clearly defines a chamfer and bevel as the same thing.

Chamfer vs break edge

break edge blueprint examples
Break edge callouts

Chamfers are often left as an afterthought for blueprint drafters. 

Many times they have no functional requirement but are merely added to protect the part and anyone who might come into contact with it from damage. Deburring an edge is very similar.

In cases where the requirements are not strict, you will often see a break edge or break all edges requirement listed.

This means the sharp edge should be removed from part, but it is not directly controlled. In cases where a break edge is specified, the drafter is generally looking for a chamfer size of .010″-.020″ and sometimes even less.

Break edge callouts will rarely be identified with an angle associated with them.

Chamfer vs countersink

Countersink Blueprint GD&T Symbol two lines pointing down
Countersink blueprint symbol

Countersinks are chamfers applied to a round feature such as a hole. 

The main difference between chamfers and countersinks is that chamfers are usually specified at 45 degrees and countersinks have a larger variety of common angles.

Countersink angles are also specified as the angle between two opposite sides of the feature. This results in the angle spec being doubled. A 45 degree chamfer would often be listed as a 90 degree countersink. Common countersink angles are 82, 90, 100 and 120 degrees.

Chamfer vs deburr

As I noted above, a deburr callout is very similar to a break edge. Deburring is the act of removing a sharp edge and often raised edges along the feature. 

Tiny bits of raised metal can be quite dangerous. Deburring will remove these sharp bits. Similar to break edges, deburr callouts are usually pretty loosey goosey.

Chamfer vs fillet

chamfer vs fillet comparison

A fillet is a rounded or radiused corner and a chamfer is a straight cut. Notice the difference in the picture above.

Chamfers do not have to be a 45 degree angle as shown in the picture above, but this is certainly the most common configuration.

How to specify chamfer dimensions

Dimensioning chamfers is done with a call out that specifies the length of the chamfer along with the angle of the chamfer. If no angle is given the chamfer is assumed to be at 45 degrees. 

Chamfers can also be specified by giving both legs of the chamfer such as:

Chamfer all edges .025″ x .025″

Chamfer notation example #1

chamfer callout blueprint note

If the example above read “Chamfer all edges and corners .030”, the callout would be the same as it is written currently.  Angles other than 45 degrees are used, but are much less frequent. 

Chamfers are often specified in the notes of a blueprint such as in the example above.

Chamfer notation example #2

chamfer callout blueprint example

In this example, the chamfer would have a leg length of .020″ and a chamfer angle of 45.00 degrees.

Measuring chamfers

How to measure the size of a chamfer

igaging pocket comparator with reticles and case
Pocket comparator, otherwise known as an eye loupe

A chamfer length or depth can be measured utilizing many different pieces of measuring equipment. Optical comparators and CMMs are often used in industry, but if you are reading this you will likely want to measure your chamfer with a gauge called a pocket comparator, often referred to as an eye loupe. 

The pocket comparator uses a magnifying lens and reticle to enable the user to measure the size of the chamfer.

How to measure the angle of a chamfer

Chamfer angles are often assumed to be the same angle as the tool used to generate them. The most common chamfer angle is 45 degrees. 

Depending on the part geometry, different tools can be used to measure a chamfer’s angle. The angle can be calculated using the triangle calculator referenced above or a protractor can be used. 

Want to learn more?

GD&T is a complicated subject and understanding it correctly can be the difference between a perfect part and scrap.

The best way to learn GD&T is from experienced teachers who can break down the material into manageable pieces.

Luckily, we know someone.

And MachinistGuides.com readers get an exclusive discount on training!

Related Articles

9 Best CNC and Machining Books

Whether you are a seasoned machinist or a machine operator starting a new career, a good book can go a long way towards developing your understanding of the parts, pieces and processes involved in the machining trade.

We have laid out our recommendations for all skill levels and even included some quality choices for topics such as CAD and GD&T.

Check out Machinist Guides picks for best machining and CNC related books!

Best Beginner Machining Book

Machining Fundamentals

It’s not quite CNC for dummies, but this text is easily the most beginner friendly book while also going in depth on the subject.

If you take a machining course, this is likely the textbook that will be used. It covers everything from manual machining to CNC and everything in between. This textbook does a good job of not assuming you have previous knowledge and instead teaches all the basics and then some in an easy-to-understand format.

One of the best things about this title is that there are a lot of pictures to show you what is being taught. There is no better beginner’s book for both manual and CNC machining.

Best Overall Machinist Reference Book

Machinery’s Handbook

This is the book by which all other references are judged. Machinery’s Handbook which is often referred to as the Machinist Handbook is the quintessential reference for all machining.

This is not a book for beginners, but instead for someone who already has some knowledge of machining. Every machine shop should and likely already does have a copy or two laying around. Each new edition continues to add new and relevant content to an already extensive collection of important information.

Don’t be afraid to pick up a previous edition if you can find it used or cheaper. The difference between one edition isn’t that great. Just avoid a copy that is five or ten editions out of date.

Every machinist should have a copy of this book available to them.

Best Beginner CNC Book

Machining and CNC Technology

Machining and CNC Technology is a great overall machining book similar to our Best Beginner Machining Book, but it was just edged out by Machining Fundamentals. 

Where this book excels is in providing an excellent introduction to CNC related topics. Too often the actual operation and setup of the machine are not given adequate coverage. This text gives them ample coverage along with many other CNC topics.

Machining and CNC Technology is another textbook that is so thorough it is often used for training in machine tool classes.

Best CNC Programming Book

CNC Programming Handbook

Not a book for beginners. The CNC Programming Handbook by Peter Smid goes in depth on just about every CNC programming related topic. Everything is covered and in great detail. Personally, this isn’t the type of text I would read straight through. Instead, I recommend using it like a CNC version of the Machinery’s Handbook.

The CNC Programming Handbook makes a great comprehensive desk reference. You won’t need it on a daily basis but when you come across a topic that you don’t understand, it will be an invaluable resource.

Best Beginner GD&T Book

2018 Ultimate GD&T Pocket Guide 

GD&T can be a complex topic to learn. Our best GD&T book recommendation is 488 pages! That’s a lot of information to take in. Luckily, there are many different “pocket guides” out there that condense it down to a beginner level so you can comprehend the basics.

This pocket guide does a good job of covering the most common applications of GD&T and it’s likely that unless you are working in inspection, it will cover everything that you need.

Even experienced inspectors can benefit from having a quick reference handy.

Best Geometric Dimensioning and Tolerancing (GD&T) Book

GD&T: Application and Interpretation 

Geometric dimensioning and tolerancing can be a difficult subject to tackle. Fortunately, this book by Bruce Wilson does a great job of breaking it down into smaller pieces.

In my opinion, when it comes it GD&T related matters, a picture says a thousand words. Luckily this book contains countless examples to make understanding some of the more difficult concepts of GD&T much simpler.

One item worth noting is that this book is based on the ASME Y14.5 2018 revision. This is the most recent revision of the drawing standard and many other textbooks available are based on older revisions of the standard. For reference, 2009 was the previous revision of ASME Y14.5.

Note: If your shop doesn’t have a copy (which they should), more experienced GD&T users may want to consider a copy of the ASME Y14.5-2018 standard to have around for reference.

Best Beginner CAD Book

Fusion 360 for Makers

If you are just getting started with CAD, then in all likelihood you will be working with Fusion 360. Fusion 360 is a free (for personal use) piece of CAD software from Autodesk, makers of Inventor.  Inventor is one of the most popular pieces of drafting software used in machine shops around the world.

Learning Fusion 360 will teach you skills which will transfer to other more advanced pieces of software. Although, I should point out that Fusion 360 is no slouch and will allow you to create some pretty advanced widgets and doodads if you take the time to learn it.

Fusion 360 for Makers is a great starting point for newbies to learn the basics and get acquainted with the software.

Best Budget Beginner Book for Lathes

Basic Lathework for Home Machinists 

If you are just getting started with lathes and are looking for a guide to start you off cheap then this is the book. It is not the most comprehensive, but it does a good job laying things out for beginners.

The abundance of pictures helps machining newbies wrap their head around the parts and processes involved with metal lathes. The only complaint would be that the pictures are in black and white which makes it a little bit harder to see some of the finer details in the photos.

If you aren’t ready to dive into a literal textbook yet, then this book can get you started at a budget friendly price.

Best Budget Beginner Book for Mills

The Milling Machine for Home Machinists

Just like Basic Lathework for Home Machinists, this book is a good starter book.

One area where The Milling Machine for Home Machinists excels is the color pictures. There are a lot of them and they make it easier to understand the topics being covered.

This is not the book you want if you have been running a mill for any length of time. It covers entry level material only. Once you fully understand the information covered, think about stepping up to one of the more comprehensive machining books for beginners such as Machining Fundamentals or Machining and CNC Technology.

Conclusion

Thanks for checking out our guide to the best machining and CNC books. Hopefully they help add to your physical and mental library.

P.S. If you have a good recommendation for a machining book please share it in the comments below.

Related articles

Thru Hole – All About

What is a thru holes?

A thru hole, also known as a through hole, is a feature on a blueprint or drawing that identifies a hole to be machined with two open ends. The hole goes all the way through the part. In other words, the hole breaks through at two locations on the part.

In the picture below, the thru hole is on the right. The other holes are blind holes.

cutaway example of blind and thru holes

How to dimension a thru hole?

A thru hole is dimensioned by specifying the diameter of the hole along with a tolerance. Additional features can be added if needed such as a countersink or counterbore for the hole. No other features are required.

Thru hole vs blind hole

A thru hole has two open ends. A blind hole has one open end and does not go all the way through the part.

Thru hole symbol

There is no GD&T symbol for a thru hole though often it will be specified with the notation “THRU” on the engineering drawing.

Thru hole examples

thru hole blueprint example

Want to learn more?

GD&T is a complicated subject and understanding it correctly can be the difference between a perfect part and scrap.

The best way to learn GD&T is from experienced teachers who can break down the material into manageable pieces.

Luckily, we know someone.

And MachinistGuides.com readers get an exclusive discount on training!

Blind Holes – All About

What is a blind hole?

A blind hole is a hole that does not go all the way through a part. A blind hole goes to a specified depth and stops. 

How to dimension a blind hole

To specify a blind hole requires listing the diameter of the hole and a dimension to control the depth. The depth can be controlled by directly specifying the depth of the hole or by identifying the amount of material that will remain.

Blind hole vs thru hole

cutaway example of blind and thru holes

A thru hole, sometimes called a through hole, goes completely through a part. It has two open ends whereas a blind hole has one open end and does not break through to the opposite side. In the image above, the three holes on the left are all blind holes. The hole on the right is a thru hole.

Blind hole symbol

Diameter Blueprint GD&T Symbol o with line through it
Diameter symbol
Depth Blueprint GD&T Symbol line with arrow pointing down
Depth of symbol

There is no GD&T symbol for a blind hole. A blind hole will be specified with a diameter and a depth specification or remaining amount of material. In the example below, the blind holes have a diameter of 0.25 and go to a depth of 0.40.

blind holes blueprint example

Can you make a flat-bottomed blind hole?

You can make a flat bottom blind hole, but it can be difficult depending upon what type of material is being drilled. A modified drill bit or an end mill can work.  This video explains some tips.

Blind hole example

The example below has three blind holes. They all have a diameter of 0.500 but they have different depths. From left to right, the depths are 0.500, 0.250 and 0.100.

blind holes blueprint example

Want to learn more?

GD&T is a complicated subject and understanding it correctly can be the difference between a perfect part and scrap.

The best way to learn GD&T is from experienced teachers who can break down the material into manageable pieces.

Luckily, we know someone.

And MachinistGuides.com readers get an exclusive discount on training!

Limit Tolerances – All About

What is a limit tolerance?

limit tolerance example

A limit tolerance is a form of dimensional tolerancing that specifies a tolerance range for a specific feature. Limit tolerances are also known as limit dimensioning and are an effective way to specify requirements on a blueprint. They clearly identify the tolerance range without requiring additional calculations by the blueprint reader.

Limit tolerance symbol

There is no GD&T symbol for a limit tolerance. Per ASME Y14.5, the notation for a limit tolerance is to callout the upper and lower tolerance boundaries for a dimension. The upper end value of the tolerance range goes on top of the lower end value as shown in the examples below.

Limit tolerance examples

limit tolerance example
limit tolerance example

Limit tolerance vs unilateral tolerance

unilateral tolerance blueprint example
Unilateral tolerance example

A unilateral tolerance lists a nominal value along with a plus or minus tolerance. Using these two values allows the blueprint reader to calculate the upper and lower ends of the tolerance range. A limit tolerance skips the calculation step and directly specifies the upper and lower end of the tolerance range. If the unilateral tolerance above was instead specified as a limit tolerance it would be 5.8-6.0.

Limit tolerance vs bilateral tolerance

bilateral tolerance blueprint example
Bilateral tolerance example

A bilateral tolerance lists a nominal value along with a plus/minus tolerance. Using these two values allows the blueprint reader to calculate the upper and lower ends of the tolerance range. A limit tolerance skips the calculation step and directly specifies the upper and lower end of the tolerance range. If the bilateral tolerance above were instead specified as a limit tolerance it would be 16.5-17.5.

Want to learn more?

GD&T is a complicated subject and understanding it correctly can be the difference between a perfect part and scrap.

The best way to learn GD&T is from experienced teachers who can break down the material into manageable pieces.

Luckily, we know someone.

And MachinistGuides.com readers get an exclusive discount on training!