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Clearance Holes vs Tapped Holes: Understanding the Differences and Applications in Onshape

Clearance Holes vs Tapped Holes: Understanding the Differences and Applications in Onshape
Discover the distinctions between clearance holes and tapped holes in Onshape. Learn the differences between tap holes and threaded holes, and how to utilize them effectively.

If you are going to work with mechanical designs, especially CAD programs such as Onshape, it is essential to understand the difference between clearance holes and tapped holes. The performance and assembly of your components can be affected by these two different holes which serve different purposes and have different specifications too. This article seeks to identify key distinctions between clearance hole and tapped hole types while looking into their peculiarities as well as suitable applications for them. Therefore, after reading this piece of writing, one should know where or why each kind of hole ought to be utilized in his/her design, thus making it efficient and functional for engineering projects at large.

What’s a Tap Hole and How Do You Use it?

What’s a Tap Hole and How Do You Use it?

Comprehending a taphole

A tap hole is often called a tap hole. It refers to a hole having internal threads machined into its walls so as to allow for secure engagement of screws or bolts. This is the understanding of threaded holes vs untapped holes. This type of hole becomes necessary when there’s a need for strong permanent fastening. Threads not only provide great holding force but also distribute load over wider area while ensuring that parts stay together firmly. Tapped holes are very convenient, especially when working with limited accessibility at the other side, such that using nuts would be impossible, hence the importance of distinguishing between threaded holes vs through holes. They find wide applications in metalworking, the automotive industry, and aerospace, where accurate and durable fastening is critical. Such accuracy is required in sheet metal works.

The steps for tapping are explained.

The tapping process involves creating internal threads inside pre-drilled holes, thereby enabling materials to be securely screwed on using bolts or screws. Normally, this process consists of three main steps: drilling, tapping and cleaning. Firstly, one drill through material up to a specific size, which corresponds with the desired thread size; this forms what we call a ‘tap drill hole.’ Secondly, insert a tool known as tap into drilled space, then rotate it so that required threads can be cut progressively from within as they move outwardly along its length. Cutting fluid has to be used at this point because it reduces friction while helping in the clearance of chips or swarf produced during the cutting operation, eventually leaving them clean without burrs or sharp edges. Lastly, clean out any metal fillings lying around inside after tapping has been done; do this until all shavings disappear completely from view, thus making sure that there’s no roughness left behind along the thread path; otherwise, joint will fail due to lack of strength caused by poor surface contact between male-female parts involved here. The accuracy with which tapping is done determines whether a strong, reliable connection will be created or not. Such connections are usually needed where high structural integrity is required. Hence, precision must be observed.

Tap vs. threaded hole.

Use a tap if you want to create internal threads within holes on materials that have limited accessibility on the other side. Choose a threaded hole when dealing with thin or soft material where a pre-existing nut can provide enough fastening strength. The decision whether to tap or use pre-threaded inserts/nuts depends much on precision and application requirements.

How to Properly Thread a Hole?

How to Properly Thread a Hole?

Choosing the correct tap-size drill

When selecting the correct tap size drill, it is important to take into account the desired thread size and type because these factors directly affect what diameter should be drilled. One way to determine which one will work is to use this formula: Tap Drill Size = Major Diameter – (1 / Number of Threads Per Inch). For example, if you were threading a 1/4-20 UNC thread, then it would be worked out as follows: 0.250″ – (1/20) = 0.200″, so you need a 7/32” bit. Furthermore, there are many standard charts available that provide quick references between taps and drill sizes, which are compatible together; also, internet calculators or phone applications can make this process even easier by ensuring accuracy when creating interior threads.

Step-by-step tapping process

  1. Prepare the hole: Ensure that the hole is clean and clear of any debris.
  2. Secure the workpiece: Clamp the workpiece tightly so it does not move.
  3. Choose the right tap: Select a tap of the correct size and type for your desired threaded hole.
  4. Lubricate the tap: Apply cutting fluid to reduce friction and heat.
  5. Line up with hole: Make sure that the tap is perpendicular to the surface.
  6. Start tapping: Rotate the tap handle clockwise, cutting into the material.
  7. Reverse to clear chips: After every few turns, rotate the tap counterclockwise to break and remove chips.
  8. Keep tapping: Repeat forward-and-reverse motion until you reach the necessary depth for threads.
  9. Take out tap: Withdraw tap carefully from its hole while keeping it aligned straightly.

Clean closer to bottom threads in order to avoid dust from affecting integrity of threaded holes. : Remove all remaining chips or debris from within threaded hole.

Frequent mistakes when threading a hole

  1. Wrong tap selection: The error of choosing an inappropriate tap for the size of the hole or type of thread.
  2. Not enough lubricating: Failure to apply adequate cutting fluid, thereby causing much friction and heat.
  3. Bad positioning: When the tap is not perpendicular to the surface of the workpiece, leading to inaccurate threads.
  4. Failure in removing chips sufficiently: Not reversing the tap often so that it clears away chips, resulting in blockages and may break taps.
  5. Too much power: Applying excessive force can either damage taps or threaded holes themselves.
  6. Over-tapping: This involves tapping beyond the required depth for threading; it can weaken threads.

What are some differences between Threaded Holes and Tapped Holes?

What are some differences between Threaded Holes and Tapped Holes?

Threaded holes vs. Tapped holes: Major distinctions

Tapped holes and threaded holes are two terms that are often used interchangeably, but they have different meanings. Specifically, a tapped hole is a hole that has been internally threaded using a tap, whereas any form of threading operation can create a threaded hole, such as thread milling or tapping. All tapped holes are threaded, but not every threaded hole is necessarily tapped – this difference reflects how they were made and with what tool.

Comparisons with tapped holes: use cases

Tapped Hole Use Cases

  • These are perfect for creating strong and accurate internal threads.
  • They are commonly used in heavy-duty applications like machines and structural assemblies.
  • Ideal for soft materials that require consistent thread cutting.

Threaded Hole Use Cases

  • These can be used for various threading operations, such as thread milling or turning.
  • This type of hole is preferred in automated or high-production environments because it offers more flexibility and efficiency during use.
  • Commonly employed where different thread types and sizes may be needed.

Tapped holes’ advantages and disadvantages

Positive sides:

  • Exactness: Gives accurate and consistent thread geometry.
  • Power: Produces strong and reliable threads for high-stress applications.
  • Flexibility: Can be used with different materials, especially softer metals and plastics.


  • Time-consuming: It takes longer time than some other threading methods because of manual setup.
  • Tool wear: Tapping tools may rapidly wear out when used in harder materials, requiring frequent replacement with third-party options.
  • Breakage risk: How can we reduce the risk of breakage while tapping threaded holes? How can we reduce the risk of breakage while tapping threaded holes? Potential tax break, which is hard to remove from the workpiece.

How can a person choose the correct tool to tap into his project?

How can a person choose the correct tool to tap into his project?

When you are choosing between a taper tap, bottoming tap, and forming tap

  1. Taper tap: This type of tool is good at beginning threads in through holes because it cuts gently.
  2. Bottoming tap: It’s perfect for threading close to the bottom of blind holes where there isn’t any passage through the material and needs precise depth control.s; has minimum lead for deeper thread cutting.
  3. Forming tap: This one works best when extruding threads into ductile materials so that strong, accurate threads are formed without cutting chips.

Thread size and drill size explanation

To get the best thread integrity and performance, it is necessary to choose the right thread size and the drill size.

  1. Size of Thread: This refers to a number assigned to the pitch diameter of an external or internal screw thread which is based on inch system units according to standard practice. The nominal diameter and pitch are indicated by this number; however, there may be additional information such as class fit designation or special thread form geometry.
  2. Drill Size: Drill sizes determine what size hole should be drilled before tapping threads into it. These holes will have different diameters depending on whether it is metric or standard measurement systems being used but they always represent smaller than final desired dimensions because some material will be removed during tapping process itself.

One can use standard charts so that they can select accurately between these two sizes which need to match up with what is recommended by their tap and also materials being worked on.

Significance of Hole Depth in Selecting a Tap

In selecting a tap, hole depth is of great importance because it determines the kind of tap required and the quality of thread produced. When dealing with shallow holes, bottoming taps are used most frequently because they can thread almost down to the bottom of the hole. Conversely, deeper holes may call for taper taps that provide progressive contact with the workpiece material, thereby securing easy cutting and lowering the chances of breaking a tap. It is crucial to ensure that the selected tap covers the entire depth of the hole without compromising on thread integrity so as to realize accurate and dependable threading outcomes.

What Are They, and What Is Their Effect on Tapping?

What Are They, and What Is Their Effect on Tapping?

The careful control of the depth is needed to define a blind hole, which does not extend throughout the material.

A blind hole stops short of complete passage through the workpiece; it has a fixed depth with a flat or slightly tapered bottom. In mold making, fastening parts together securely, and creating accurate cavities for inserts or plugs, among other applications, it is common for blind holes to be adopted where having through-holes would compromise the appearance, function, or integrity of the component. Because they are limited in terms of their depths, taps need to be selected carefully so that chips can be removed easily and quickly, thus reducing tap breakage chance while ensuring that no time is wasted during this process.

Tapping challenges with a blind hole

Unique problems arise when tapping blind holes, mostly because there isn’t much room for chips to collect. This means spiral flute taps become necessary since these types of taps have been designed specifically for removing chips from blind holes quickly and efficiently, thereby preventing any blockages from occurring, which may result in smooth operation failure. It is also crucial that you control your depth accurately so as not to bottom out since this might cause breakage of taps too. Appropriate lubrication will help reduce friction between workpieces being tapped and taps themselves, hence lowering the chances for such tools, as well as materials, getting damaged due to heat build-up caused by excessive rubbing.

Techniques that work for tapping into blind holes

Use the correct taps and tools: Choose spiral flute taps designed specifically for blind holes.

  • Control depth: This is important, especially when dealing with blind holes where the hole does not go through the material. Use tapping stations that have accurate depth stop settings to avoid bottoming out.
  • Lubricate: Apply good quality tapping lubricants in order to reduce friction and heat build-up.
  • Evacuate chips: Reverse the tap occasionally to clear chips so as to have efficient chip removal.
  • Speed and feed rate: Run at recommended speed and feed rate for the material being used to maintain thread integrity.

Questions and answers about drilled holes

Questions and answers about drilled holes

Drilled hole vs. Tapped hole

A drilled hole is a simple opening in any material that does not have threads in it. Commonly, bolts or screws are put into them to hold things together. The difference from the latter is that a tapped hole usually refers to internal threads made by using a tap which allows for direct insertion of threaded fasteners as well as holding them there.

What do you do if your tap breaks off in the middle of threading?

When a part has been threaded but its tap snaps inside itself, there may be different ways to deal with this situation. One option is using tap extractors; these are tools designed specifically for removing broken taps. Another possibility involves electrical discharge machining (EDM), which can dissolve the stuck piece metalically until it falls out naturally. Drilling out what remains still attached might work, too. Anyhow, these methods may require certain expertise and take time, so they will cause longer periods of non-operation while damaging workpieces, which should be avoided at all costs during the tapping process done carefully.

What is the method to ensure threads run through a hole that has been tapped?

To make sure that threads run through a hole that has been tapped, do the following:

  1. Choose the Right Tap: Select a tap of suitable size and type for both the material and depth of the hole. For blind holes, it is advisable to use spiral flute taps as they aid in chip removal.
  2. Tapping Method: Maintain an even rhythm while tapping by applying constant pressure. This ensures that the entire length of the hole is engaged with the tap.
  3. Cooling and Lubrication: Friction should be reduced by smearing some high-quality cutting fluid on or around areas where cuts are being made during tapping. Heat buildup can also be prevented this way; besides it makes cutting easier.
  4. Control Over Depth: Use tapping tools fitted with stoppers for controlling depth or taps having marks indicating how deep they should go into materials so that over-tapping does not occur nor under-tapping happens.
  5. Checking: After tapping, confirm thread presence along all parts of a hole by using either an appropriate-sized fastener or thread gauge.

Following these procedures will enable you to achieve accurate and consistent, fully-threaded holes once they have been tapped.

Reference Sources

Reference Sources


Threading (manufacturing)

Screw thread

Frequently Asked Questions (FAQs)

Q: What is the main difference between clearance holes and tapped holes?

A: Their purpose and making are what creates the biggest disparity between clearance holes and tapped ones. A person makes a clearance hole so that it may allow a fastener to pass through without engaging threads, on the other hand, threads are cut into tapped holes to engage fasteners. In Onshape, both types of holes can be easily created using the feature called hole.

Q: When should I use a clearance hole vs. a tapped hole?

A: Use a clearance hole if you want a fastener to go through material freely before nut or threaded hole engagement on the other side while if you want the material itself to act as the nut then provide more permanent and precise fastening solution use tapped hole.

Q: How do I specify the size of a clearance hole in Onshape?

A: Screw-clearance option is selected from among those listed under the screw-clearance dialog box in order for machinists to use CNC machining accurately and create the required sizes of such screw clearances.

Q: Can Onshape help with creating threaded holes?

A: Threaded holes can be created by selecting threading process within hole feature which helps ensure that your selected type of fastener has been correctly tapped for example UNC UNF metric threads this setting may however not work well according to some callout specifications regarding creation of these types of features so one needs be careful when making them.

Q: What are the most common uses of clearance holes in relation to tapped holes when it comes to CNC machining?

A: When it comes to CNC machining, there are a few different applications for these two types of holes. In assembly processes where fasteners need to pass through multiple parts and be secured with nuts or other means on the opposite side(s), clearance holes might be employed. On the other hand, within one piece itself, tapped holes could be used as an alternative way to fasten without using nuts at all.

Q: Can I create both types of holes with the same tool?

A: Usually, different tools are required to make a clearance hole compared to those needed for tapping. That being said, though, drills can bore out clearances while taps cut internal threads into them, so you may not always need separate ones if working on certain projects where space is limited, but this would still depend upon what type(s) were being made.

Q: What should I consider when choosing between cutting taps and thread-forming taps as threading processes?

A: The main factors that should come into play when deciding which process will work best for you include – the material being worked with, the desired finish on the thread(s), and also the application/end use intended for a part in question. Taps that remove material (cutting) can be used across many different materials, whereas those that displace it (forming) often provide stronger threads within ductile ones like aluminum, etc. Additionally, the choice may depend upon the level of detail needed, such as high-precision prototyping.

Q: Are there any pros or cons associated with clearance holes?

A: There are definitely some advantages and disadvantages associated with their usage, too. For example, they allow faster alignment during assembly because bolts just slide right through without catching on anything, but once again, this means there needs to be a nut present on the opposite side, so if access isn’t available from both sides, then one more step must be performed, which is putting on the nut. This can cause problems when working within tight spaces or where it is hard to reach, etc.

Q: When might 3D printing be beneficial for creating tapped holes?

A: In certain cases, such as during prototype development, 3D printing could prove useful in making threaded openings. It enables quick iterations and tests without having to use traditional machining methods that take longer time periods. Nevertheless, the strength of threads produced by additive manufacturing might not always match up against those created via cutting tools depending upon the chosen material type and print resolution used, hence making them more suitable for nonload bearing applications or just concept testing in general.

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Mr.Ting.Liang - CEO

Greetings, readers! I’m Liang Ting, the author of this blog. Specializing in CNC machining services for twenty years now, I am more than capable of meeting your needs when it comes to machining parts. If you need any help at all, don’t hesitate to get in touch with me. Whatever kind of solutions you’re looking for, I’m confident that we can find them together!

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