Types of Holes - The Complete Guide | The Engineer's Bible (2024)

  • Types of Holes - The Complete Guide | The Engineer's Bible (1)byThe Engineer's Bible
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  • Updated:
  • 07-Oct-2022

Types of Holes - The Complete Guide | The Engineer's Bible (2)

This is a complete guide to the types of holes found in machining.

In this guide you’ll learn:

  • The different types of holes used in machining.
  • What the difference is between counterbore and countersink holes.
  • The symbols used for each hole and how they are shown on engineering drawings.
  • How each type of hole is used in engineering.

So if you want to learn the different types of holes used in engineering, you’ll love today’s guide.

Let’s get started.

Table of Contents

Simple Hole

What Is a Simple Hole?

A simple hole is a circle that has been cut out of an object.

If we cut the block in half, it looks like this:

What Is the Symbol for a Simple Hole?

The symbol used for a hole is the diameter ‘Ø’ symbol.

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How Are Simple Holes Shown on Engineering Drawings?

Simple holes are shown on engineering drawings by stating the diameter and the depth of the hole.

For example, a 20 diameter hole that goes straight through the component would be represented as “Ø20 Through”.

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Holes that go all the way through the component are known as through holes.

Holes that do not go completely through the material are known as blind holes.

Holes can be shown as a section view in order to show a clearer image of the depth of the holes.

The bottom view is what we would see if we cut the top view in half along the ”A’ section line.

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The shape of the bottom of the hole is determined by the tool used to create the hole.

For a drilled hole, the shape of the bottom of the hole will be determined by the drill tip angle.

If the hole is created by a process called ‘boring’ or by a tool with a zero tip angle, the bottom of the hole will be flat.

These two types of blind hole drilling are shown in the drawing below:

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Counterbore

What Is a Counterbored Hole?

A counterbore is a simple hole with a wider hole above it.

The 3D model below shows a counterbore with the same counterbore next to it cut in half:

What Is the Counterbore Symbol?

The symbol used for a counterbore is ‘⌴’.

Types of Holes - The Complete Guide | The Engineer's Bible (7)

How Are Counterbores Shown on Engineering Drawings?

Counterbored holes are shown on engineering drawings as follows:

Types of Holes - The Complete Guide | The Engineer's Bible (8)

The top view shows how counterbored holes are shown on drawings. The bottom view explains what the counterbore dimensions are showing.

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Note for counterbored holes that the pilot hole usually goes completely through the component. That’s why there isn’t a ‘Through’ or a dimension after the pilot hole diameter, because it is assumed it goes all the way through.

A ‘pilot hole’ is a small diameter hole, usually the first hole to be drilled.

The counterbore example above was for an M20 socket-head bolt with normal clearance. You can find out what size counterbore you need by looking at a chart such as this one.

What Are Counterbored Holes Used For?

Counterbores are machined for socket-head screws. They are used for applications where the bolt or screw must sit beneath the surface.

For example, in applications where there isn’t space for a hex-head bolt to be used due to clearance issues:

Types of Holes - The Complete Guide | The Engineer's Bible (10)

A washer may also be present underneath the socket-head screw.

Spotface

What Is a Spotface?

A spotface is a shallow counterbored hole.

What Is the Spotface Symbol?

The symbol for a spotface is the counterbore symbol with the letters ‘SF’ inside it:

Types of Holes - The Complete Guide | The Engineer's Bible (11)

How Are Spotfaces Shown on Drawings?

An example of a spotface is shown below, the dimensioning is very similar to a counterbore.

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What Are Spotfaces Used For?

Spotfaces are used for creating a smooth and flat surface.

For example, a component that has been made via casting may not have a smooth and flat surface like a machined component.

Therefore a spotface is machined, ensuring that a part to be connected to a component with a rough surface is located correctly.

Countersink

What Is a Countersunk Hole?

A countersink is a simple hole with a conical hole above it.

The 3D model below shows a countersink with the same countersink next to it cut in half:

What Is the Countersink Symbol?

The symbol for a countersink is ‘⌵’.

Types of Holes - The Complete Guide | The Engineer's Bible (13)

How Are Countersinks Shown on Drawings?

Countersunk holes are shown on drawings as follows – the bottom section view shows what the top dimension refers to.

Types of Holes - The Complete Guide | The Engineer's Bible (14)

If the countersink was a blind hole, the ‘Through’ above would be replaced with the depth of the pilot hole.

You may be wondering what the ‘Ø40.32′ is. This is known as the theoretical edge and this size countersink is for an M20 countersunk bolt.

You can find out the countersunk dimension required for countersunk metric bolts here.

What Are Countersunk Holes Used For?

Countersunk holes are used for applications where a countersunk bolt or screw is required.

Like counterbore holes, countersink holes ensure the bolt or screw sit below the surface.

Types of Holes - The Complete Guide | The Engineer's Bible (15)

Counterdrill

What Is a Counterdrilled Hole?

A counterdrilled hole is like a countersunk hole but there is a recess above it.

The 3D model below shows a counterdrilled hole with the same counterdrilled hole next to it cut in half:

What Is the Counterdrill Symbol?

The symbol for a counterdrill is the same as a countersink (⌵) but there will be a depth stated as well.

Types of Holes - The Complete Guide | The Engineer's Bible (16)

How Are Counterdrills Shown on Drawings?

Counterdrilled holes are shown on drawings as follows – the bottom section view shows what the top dimension refers to.

A counterdrill can also be stated as C’DRILL or CDRILL on an engineering drawing.

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Taper

What Is a Tapered Hole?

A tapered hole is one where the start diameter of the hole is a different to the end diameter of the hole.

Below is a 3D model of a tapered hole next to the same hole cut in half:

What Is the Tapered Hole Symbol?

The taper symbol is:

Types of Holes - The Complete Guide | The Engineer's Bible (18)

How Are Tapered Holes Shown on Drawings?

Tapered holes can be shown in a number of different ways on engineering drawings.

An example of a drawing showing a tapered hole is below:

Types of Holes - The Complete Guide | The Engineer's Bible (19)

The taper in the above example is 1:5. The end diameter has been left on for reference (in brackets).

To work out what the end diameter use the equation:

Types of Holes - The Complete Guide | The Engineer's Bible (20)

Types of Holes - The Complete Guide | The Engineer's Bible (21)

Tapered holes can also be shown without the taper symbol when dimensioning using an angle is more important:

Types of Holes - The Complete Guide | The Engineer's Bible (22)

What Are Tapered Holes Used For?

Tapered holes have lots of different engineering applications.

A common example is using a tapered hole to secure cutting tools or other tool holders.

Screw Clearance

What Is a Screw Clearance Hole?

A screw clearance hole is exactly that.

It’s a simple hole that has a slightly bigger diameter than the screw thread so that the screw can pass through.

What Is the Screw Clearance Symbol?

Screw clearance holes are shown as simple holes, and use the ‘Ø’ diameter symbol.

How Are Screw Clearance Holes Shown on Drawings?

Screw clearance holes are shown as simple holes:

Types of Holes - The Complete Guide | The Engineer's Bible (23)

What Size Screw Clearance Hole Should I Use?

You can use the metric guide for screw clearance holes or the imperial guide for screw clearance holes.

What Are Screw Clearance Holes Used For?

Screw clearance holes are used for components that need the screw or bolt to go through them.

An example of this is a bracket that needs to be attached to a block.

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The bracket has screw clearance holes so that a bolt can pass through it.

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Types of Holes - The Complete Guide | The Engineer's Bible (26)

The bolt is threaded into the block which has a tapped hole.

Types of Holes - The Complete Guide | The Engineer's Bible (27)

The compression force of tightening the bolt fixes the bracket to the block.

Tapped Hole

What Is a Tapped Hole?

A tapped (or threaded) hole is a hole that has a thread.

What Is the Tapped Hole Symbol?

The symbol for a tapped hole depends on the standards used. For metric holes, the diameter symbol is replaced with an ‘M’. For example a tapped hole for an M8 bolt would be ‘M8’.

For different types of threads, for example a Unified National Fine (UNF) thread, the numerical dimension is shown first then the thread type “UNF”.

How Are Tapped Holes Shown on Drawings?

Tapped holes are shown on drawings as follows:

Types of Holes - The Complete Guide | The Engineer's Bible (28)

The “2.5” is the pitch of the thread, which is the distance in millimeters between each thread.

For a UNF thread, a through 1½” 12 hole would look like this:

Types of Holes - The Complete Guide | The Engineer's Bible (29)

The ’12’ means that there are 12 threads per inch.

What Are Tapped Holes Used For?

Tapped holes are used to hold threaded components. Examples include screws, bolts and threaded rods.

Enjoyed this post? Check out our types of welds post.

Conclusion

We hope you enjoyed our new types of holes guide.

Now we’d like to hear what you have to say:

Which type of hole did you learn today?

Or which type of hole do you use most often?

Let us know by leaving a comment below right now.

  • 25 Comments
  • 25 Comments

25 thoughts on “Types of Holes – The Complete Guide”

  1. Types of Holes - The Complete Guide | The Engineer's Bible (30)

    john

    22 November 2021 at 10:25

    Thanks for this info. Been a while.

    Reply

    1. Types of Holes - The Complete Guide | The Engineer's Bible (31)

      The Engineer

      23 December 2021 at 18:25

      Thanks John, glad you enjoyed it!

      Reply

    2. Types of Holes - The Complete Guide | The Engineer's Bible (32)

      Gaurav Patel

      27 April 2023 at 09:27

      Very useful article ❤️❤️.

      Reply

  2. Types of Holes - The Complete Guide | The Engineer's Bible (33)

    Valeriy

    4 December 2021 at 09:02

    Very useful article!
    Thanks

    Reply

    1. Types of Holes - The Complete Guide | The Engineer's Bible (34)

      The Engineer

      23 December 2021 at 18:26

      Thanks Valeriy!

      Reply

  3. Types of Holes - The Complete Guide | The Engineer's Bible (35)

    20 December 2021 at 08:19

    If I have a tapped hole and counter bore feature on the periphery of a round face, would the tapped hole depth still start from the imaginary arc, or from the bottom of the counter bore? I can’t find any specific drafting standard that shows this but looking at the spot face example, it would seem that the tapped hole depth would be understood to start from the circular face, and not the first flat face at the bottom of the counter bore?

    Reply

    1. Types of Holes - The Complete Guide | The Engineer's Bible (36)

      The Engineer

      23 December 2021 at 18:23

      Hi Nick, great question.

      Usually the smaller diameter (pilot) hole is the first dimension given for a counterbored hole, and this is the same for a hole with a spotface (i.e. the M20 hole dimension comes before the 50 mm diameter spotface dimension above).

      A good way to imagine this is as if you are machining the tapped hole first and then the spotface (so the tapped hole starts at the imaginary arc in your example).

      To stop any potential ambiguity in the engineering drawing of your imaginary arc example, a section view with individual dimensions for the depth could be used instead.

      Reply

  4. Types of Holes - The Complete Guide | The Engineer's Bible (37)

    ly

    30 December 2021 at 01:29

    Is it a through hole through which cables go?

    Reply

    1. Types of Holes - The Complete Guide | The Engineer's Bible (38)

      The Engineer

      30 December 2021 at 09:08

      It depends on if the cables go through the whole component or not. If using electrical conduit then this pipe could be seen as a through hole for the cable.

      If the cable does not go all the way through the component, such as the hole for a hotend sensor in a 3D printer heater block, then this would be a blind hole.

      Reply

  5. Types of Holes - The Complete Guide | The Engineer's Bible (39)

    Nagma

    11 January 2022 at 07:14

    Thanks a lot for Detailed explain along with 3D

    Reply

    1. Types of Holes - The Complete Guide | The Engineer's Bible (40)

      The Engineer

      11 January 2022 at 19:47

      You’re welcome Nagma, glad you enjoyed the 3D CAD models!

      Reply

  6. Types of Holes - The Complete Guide | The Engineer's Bible (41)

    15 May 2022 at 13:55

    what does C’Drill (Only K ) mean? please help.

    Reply

    1. Types of Holes - The Complete Guide | The Engineer's Bible (42)

      The Engineer's Bible

      8 June 2022 at 20:44

      Hi Tuong, C’Drill is referencing a counterdrilled hole and this article has now been updated to explain counterdrilled holes.

      It’s hard to say what the ‘Only K’ is refering to without seeing the drawing. Perhaps it’s just the one instance to be counterdrilled?

      Reply

  7. Types of Holes - The Complete Guide | The Engineer's Bible (43)

    mello

    7 June 2022 at 07:11

    Hello po ,what other term for counterdrill holes?

    Reply

    1. Types of Holes - The Complete Guide | The Engineer's Bible (44)

      The Engineer's Bible

      8 June 2022 at 20:46

      Hi Mello, another term for a counterdrill hole could be “C’Drill” or “CDRILL” on an engineering drawing.

      We have added another 3D model to explain counterdrilled holes in more detail.

      Reply

  8. Types of Holes - The Complete Guide | The Engineer's Bible (45)

    Mohamed

    7 August 2022 at 15:17

    Thanks you. very well explained.

    Reply

  9. Types of Holes - The Complete Guide | The Engineer's Bible (46)

    Paritosh

    24 December 2022 at 12:50

    What is meaning of H7, if wirte as
    “dia 16 H7 thru”

    Reply

    1. Types of Holes - The Complete Guide | The Engineer's Bible (47)

      The Engineer's Bible

      4 January 2023 at 19:52

      Hi Paritosh!

      “H7” is the tolerance of the diameter of the hole. If using an ISO limits and fits table, this means that the final measured diameter of the hole needs to be between 16.018 mm and 16.000 mm.

      Reply

  10. Types of Holes - The Complete Guide | The Engineer's Bible (48)

    TokiW

    4 February 2023 at 23:24

    Can someone explain the following?
    Ø5.5±0.04 ↧ – A – (10.12)
    As I understand, it means that the depth of the given hole is until datum A and than the dimension in parenthesses provides the estimated value in mm? Am I correct?

    Reply

  11. Types of Holes - The Complete Guide | The Engineer's Bible (49)

    chris

    26 April 2023 at 02:22

    I’ve learned a lot thanks!

    Reply

    1. Types of Holes - The Complete Guide | The Engineer's Bible (50)

      The Engineer's Bible

      26 April 2023 at 13:21

      That’s great to hear Chris 😊

      Reply

  12. Types of Holes - The Complete Guide | The Engineer's Bible (51)

    Raj

    12 August 2023 at 04:04

    simple explanation with clear diagram.

    Reply

  13. Types of Holes - The Complete Guide | The Engineer's Bible (52)

    vincent

    14 August 2023 at 06:49

    wow this website helps me a lot at my school, thank you so much !!

    Reply

  14. Types of Holes - The Complete Guide | The Engineer's Bible (53)

    Fortune

    23 August 2023 at 06:06

    Love this,thanks

    Reply

  15. Types of Holes - The Complete Guide | The Engineer's Bible (54)

    Jim Walton

    8 March 2024 at 14:50

    Thanks

    Reply

Leave a Comment

Types of Holes - The Complete Guide | The Engineer's Bible (2024)

FAQs

What are the different types of holes in engineering? ›

Below I'll provide an overview of twelve types of holes in engineering: the blind hole, through hole, interrupted hole, simple hole, counterbole hole, spotface hole, countersink hole, counterdrill hole, tapered hole, screw clearane hole, tapped hole, and threaded hole.

What is the blind hole symbol? ›

The callout symbol for a blind hole is typically represented by a circle with a perpendicular line at the center extending halfway into the circle, indicating the depth of the blind hole.

What are the different types of holes in structural steel? ›

Standard holes and short- slotted holes can be used in each of the joint types. Long-slotted holes are permitted in each of the joint types with the approval of the Engineer of Record, while oversized holes can be used only in slip-critical joints.

What are the different types of through holes? ›

There are two main types of thru-hole components — axial lead and radial lead. Axial lead components have leads on both ends. They come out of the part in a straight line. Radial lead components have both leads on one side.

What is the difference between tapped and threaded holes? ›

Key Differences:

Tapped holes require a pre-drilled hole, while threaded holes can be created without pre-drilling. Tapped holes are typically used in applications where the fastener needs to be removable, while threaded holes are used in applications where the fastener needs to be permanently fixed.

What is the difference between a blind hole and a through hole? ›

A through hole or thru-hole is a hole that goes all the way through a part with two open ends. Inversely, a blind hole has one open side and an opposite side which the hole doesn't break through. A blind hole has a specified depth.

What is the hidden line symbol in engineering drawing? ›

A hidden line, also known as a hidden object line is a medium weight line, made of short dashes about 1/8” long with 1/16”gaps, to show edges, surfaces and corners which cannot be seen.

What is the symbol for a hole? ›

The callout symbol of the through hole is similar to that of a simple hole which is the diameter 'Ø symbol. It simply means if you have a 10-diameter hole in the material, it will be shown as ''Ø10 Through'' in the drawings.

How do you call out a tapped hole in drawing? ›

You can add hole callouts in standard drawing views and in section views. To add a hole callout: Click Hole Callout (Annotation toolbar), or click Insert > Annotations > Hole Callout.

What is the counterbore symbol in engineering drawing? ›

Callout Symbols

The '⌴' symbol is used to indicate a counterbore hole on engineering drawings. The depth number and the diameter symbol are also included for counterbore holes. Spotface indications do not have their own symbol but instead, use the counterbore symbol with the letters 'SF' inside it.

What does 🕳 mean? ›

A round, black, cartoon-styled hole, as a manhole or a hole (cup) in golf. May be used to represent various types of literal or figurative holes, e.g., black holes, rabbit holes. Hole was approved as part of Unicode 7.0 in 2014 and added to Emoji 1.0 in 2015.

What is the important symbol in holes? ›

In the book, onions symbolize health. At the beginning of the story, Sam, the onion man, sold onion products to people who were having health issues. Also, when Stanley and Zero were trying to get back to Camp Green Lake, they came across an onion patch.

What is the Symol hole? ›

The Mysterious Symol Hole is a hidden little spot in the heart of Meridell, which your Neopet can visit with its petpet for a chance to win Neopoints, a prize, or even an avatar! Though it is unlabeled on the map, we have pointed it out for you below; you can also locate it yourself to the right of the Turmaculus.

What are the different types of hang holes? ›

Common types include round hanger holes, euroslots, inverted-T holes, and osha holes–each offering unique benefits in terms of stability, visibility, and ease of use.

What are the different types of sound holes? ›

C-holes, D-holes and F-holes are usually made in pairs placed symmetrically on both sides of the strings. Most hollowbody and semi-hollow electric guitars also have F-holes. Though sound holes help acoustic instruments project sound more efficiently, sound does not emanate solely from the sound hole.

How many hole types are there in hole command? ›

You can use the Hole command to construct simple, threaded, tapered, counterbored, and countersunk holes.

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