CNC Mill Tutorials - 5 - Drilling, Reaming, Tapping and Boring

Summary

In this instructional video, viewers learn the process of drilling, tapping, and reaming in metalworking. The tutorial covers drilling five distinct holes, including a half-inch through hole, a reamed hole, a tapped hole for a 1/2-13 threaded bolt, a counterbored hole, and a countersunk hole. Key techniques such as center drilling, using cutting oil, and proper RPM settings are emphasized for precision and accuracy in machining.

Takeaways

• 🛠️ The video demonstrates how to drill, tap, and ream holes for various purposes.
• 🔩 It covers the process of drilling five different types of holes: a half-inch through hole, a reamed hole, a tapped hole for a threaded bolt, a counterbored hole, and a countersunk hole.
• 📏 The first hole is drilled using a half-inch drill bit, run at low range RPM with cutting oil for lubrication.
• 🔧 A reamed hole is prepared by initially drilling with a 31/64 inch bit, then reaming to achieve the exact size.
• 🗜️ The third hole is drilled to a depth of 3/4 inch and tapped for a 1/2-13 threaded bolt, using a 27/64 inch drill bit as per the tap reference chart.
• 🔩 Tapping is performed using a gun tap for starting threads and a bottoming tap to complete the threads to the bottom of the hole.
• 🔩 The process of tapping involves applying constant pressure, using cutting oil, and alternating between screwing in and backing out to clear chips.
• 🔩 A counterbored hole is drilled by first drilling a half-inch through hole and then raising the knee to achieve the desired counterbore depth.
• 🔩 A countersink is added to a 3/8-inch through hole using an 82-degree countersink bit, ensuring proper alignment with a bottom guide pin.
• 🛠️ The process emphasizes the importance of using cutting oil, maintaining proper pressure, and checking the accuracy of the work with the actual bolt or screw.

Q & A

How many holes are planned to be drilled in the video?

Five holes are planned to be drilled.

What is the size of the first hole to be drilled?

The first hole is a half-inch through hole.

What is the purpose of reaming a hole?

Reaming is used to bring a hole to an exact size, which is why a 31/64 drill bit is used before reaming the second hole.

What is the depth of the hole that is tapped for a 1/2-13 threaded bolt?

The depth of the hole for the 1/2-13 threaded bolt is 3/4 inch.

What size drill bit is used for the hole that will be tapped for a 1/2-13 threaded bolt?

A 27/64 drill bit is used for the hole that will be tapped for a 1/2-13 threaded bolt.

Why is a counterbore performed on the half-inch through hole?

A counterbore is performed to create a flat surface around the hole to allow a bolt head to sit flush.

What is the purpose of using a center drill before drilling the actual holes?

Center drilling acts as a pilot to prevent larger drill bits from wobbling or walking on the surface.

What is the significance of the scratch marks being inconsistent on the forward hole?

Inconsistent scratch marks on the forward hole indicate that the hole may not be as accurate as the reamed hole, which appears shiny and more accurate.

What are the two types of taps used in the video?

The two types of taps used are the gun tap, which is more aggressive for starting threads, and the bottoming tap, which allows threads to reach the bottom of the hole.

How is cutting oil applied during the tapping process?

Cutting oil is applied before the tapping process begins and is used throughout to ensure smooth operation and reduce friction.

What is the purpose of the bottom guide pin on the counterbore bit?

The bottom guide pin on the counterbore bit ensures proper alignment during the counterboring process.

How is the depth checked during the countersinking process?

The depth during the countersinking process is checked by going down a certain depth, checking it with the bolt, and then iterating until it is fine and within tolerance.

Outlines

00:00

🔧 Drilling, Tapping, and Reaming Overview

This section introduces the tasks that will be covered in the video, which include drilling, tapping, and reaming. It details the five holes to be drilled: a half-inch through hole, a reamed half-inch hole (using a 31/64 drill bit), a tapped hole (for a 1/2-13 threaded bolt), a counterbored hole, and a 3/8-inch hole with a 82-degree countersink. The importance of centerdrilling to avoid wobbling or walking is emphasized, as well as using cutting oil for lubrication and coolant. The process begins with drilling the half-inch through hole at the specified RPM.

05:03

🛠️ Reaming and Tapping Techniques

Here, the reaming process for the half-inch hole is explained. A 31/64 drill bit is used to prepare the hole, which is then reamed to the exact size using a reamer. Emphasis is placed on applying constant pressure during reaming and maintaining proper lubrication. The section also covers the process of tapping a 1/2-13 threaded hole using a 27/64 drill bit and cutting oil. Both the gun tap and bottoming tap are used to create the threads. Key techniques, such as keeping constant pressure on the tap and backing off to cut chips, are highlighted.

Keywords

💡drilling

Drilling refers to the process of creating a round hole in a solid material by using a rotating cutting tool, known as a drill bit. In the video, drilling is the first step in creating holes for various purposes. For instance, a half-inch through hole is drilled using a half-inch drill bit, and a 27/64 drill bit is used to prepare a hole for tapping.

💡reaming

Reaming is the process of smoothing and enlarging a previously drilled hole to a precise size using a tool called a reamer. In the script, after drilling a hole with a 31/64 drill bit, a reamer is used to achieve the exact half-inch size, which is crucial for fitting a bolt or other components accurately.

💡tapping

Tapping is the process of cutting internal screw threads into a hole. The video describes tapping a hole for a 1/2-13 threaded bolt, which involves using a 27/64 drill bit to prepare the hole, followed by threading it with a tap. This process is essential for creating threads that can accept screws or bolts.

💡counterboring

Counterboring is a machining process where a flat-bottomed hole is created to allow the head of a bolt or screw to sit flush with the surface. In the video, after drilling a half-inch through hole, a counterbore is made to a depth of half an inch, ensuring that the bolt head sits flush when assembled.

💡countersinking

Countersinking is a process similar to counterboring but with a conical shape, which allows for the head of a screw or bolt to sit below the surface. The video mentions using an 82-degree countersink bit to create a conical recess for a 3/8-inch through hole, which is useful for a flush finish.

💡centerdrilling

Centerdrilling is the initial step in drilling where a small pilot hole is made at the exact center of the desired final hole. This prevents the larger drill bits from wandering or wobbling. The script mentions centerdrilling each hole before proceeding with larger operations, which ensures accuracy and precision.

💡RPM

RPM stands for revolutions per minute and is a measure of the rotational speed of a drill bit or other rotating machinery. The video specifies that the mill should be run at a low range RPM as recommended by the machinist, which is crucial for controlling the drilling speed and preventing overheating or damage to the workpiece.

💡cutting oil

Cutting oil is a lubricant used to reduce friction and dissipate heat during machining processes like drilling, reaming, and tapping. The script emphasizes the use of plenty of cutting oil for lubrication and coolant, which is essential for prolonging tool life and ensuring a smooth operation.

💡tap reference chart

A tap reference chart is a guide that provides information on the correct size of the drill bit to use for a given tap size and thread type. In the video, the chart is consulted to determine that a 27/64 drill bit should be used for a 1/2-13 threaded hole in aluminum, demonstrating the importance of such charts in precision machining.

💡threaded bolt

A threaded bolt is a type of fastener with external screw threads, used to join parts together by passing through holes in the parts and tightening with a nut or by threading it into a pre-threaded hole. The video discusses tapping a hole for a 1/2-13 threaded bolt, which is a specific type of bolt with a diameter of 1/2 inch and 13 threads per inch.

💡machinist

A machinist is a skilled tradesperson who operates machine tools to create or modify parts. In the context of the video, the machinist provides specifications such as the correct RPM for drilling and tapping operations, highlighting the expertise required in machining processes.

Highlights

Introduction to drilling, tapping, and reaming processes.

Plan to drill five different holes with specific operations.

First hole is a half-inch through hole.

Second hole will be a half-inch reamed hole.

Third hole is a 3/4-inch deep hole tapped for a 1/2-13 threaded bolt.

Fourth hole is a half-inch through hole to be counterbored.

Fifth hole is a 3/8-inch through hole with an 82-degree countersink.

Centerdrilling each hole to prevent wobbling.

Programming the position of holes with the top left as the origin.

Using a half-inch drill bit for the first through hole.

Running the mill at low range with specified RPM and using cutting oil.

Using a 31/64 drill bit for the reamed hole.

Applying constant pressure while reaming without backing out.

Drilling and tapping the 3/4-inch hole using a 27/64 drill bit.

Using a gun tap for ease of starting threads.

Re-tapping with a bottoming tap to ensure threads reach the bottom of the hole.

Ensuring proper alignment and applying cutting oil during tapping.

Checking the fit of the bolt after tapping.

Finishing the counterbore half-inch hole with a bottom guide pin for alignment.

Drilling the counterbore in low range with cutting oil.

Finishing the 3/8-inch through hole with an 82-degree countersink.

Iterating the countersink depth to ensure a proper fit with the bolt.

Transcripts

Today we are going to learn how to drill, tap, and ream.

Lets talk about it.

*intro music*

Today we will be drilling five holes

The first hole will be a half inch through hole.

The second will be a half inch reamed hole, that will first be drilled with a 31/64 drill bit

Then a 3/4 inch deep hole, that will be tapped for a 1/2-13 threaded bolt.

This hole will first be drilled with a 27/64 bit.

This info was found on the tap reference chart.

Then we will drill a half inch through hole that will then be counterbored to the depth

of half an inch.

Lastly, we will drill a 3/8 inch through hole then add a 82 degree countersink.

We will first centerdrill each hole.

This acts as a pilot and prevents the larger drill bits from wobbling / walking on the

top of the surface.

We have additionally programmed the position of these holes the top left being the origin.

Now we are going to be drilling our half inch through hole, and you guessed it, we are going

to be using our half inch drill bit.

We are going to be running the mill in low range at the specified RPM given by the machinist

and going to be using plenty of cutting oil for lubrication and coolant.

Now we will be doing our reamed half inch through hole, we cannot directly use a half

inch drill bit, so we will instead use a 64th smaller.

That will allow us to use a reamer to bring it to the exact size.

So with our 31/64th drill bit in the chuck, we can now begin to drill in low range

using plenty of cutting oil.

We now have the 0.500 reamer in the chuck.

Note that when using a reamer, we need to apply constant pressure, and will not be backing

out at all, while still using plenty of cutting oil.

We have the RPM set to the specified value given by the machinist.

Note on the forward hole the scratch marks are inconstant, and the reamed hole on the back,

everything looks shiny.

AKA more accurate.

Next we are going to drill and tap our hole.

We have already set our desired depth and have moved up the knee 3/4 of an inch.

Using a tap chart we have found that for a 1/2-13 hole, we are going to use a 27/64 drill

bit through aluminum.

We have our drill bit setup and we will still use cutting oil.

Now we have the hole drill, we can begin to tap.

We will first use the gun tap, which is the gold one.

Notice it has a more aggressive tapper, which allows for the ease of starting threads.

We will re-tap using the bottoming tap, which

allows threads to get to the bottom of the hole

With the tap center in the chuck, we can now put the top of the tap center in the top of

the tap, and the tap in the hole.

Be sure that the tap center has constant pressure on the tap to align everything up.

And after applying cutting oil.

Use both hand during the tapping process, and after a few turns

you can then back off to cut chips.

Once we think we are getting to the end we need to apply constant pressure, not a lot

of pressure, but pulling up with both hands.

Because we do not want to cut the first thread twice.

There we go.

So our first tapping job is done.

Now we will tap with the bottoming tap.

We will put it in, just as before.

Top of the tap center in the top of the tap, and the tap in the hole.

Apply cutting oil.

And screw in a few more turns, and back out to cut any chips.

And there we go.

Hole is now tapped

Might need a slight cleaning.

We will see if our bolt fits.

Seems to be tapped well.

Now we are going to finish our counterbore half inch hole.

We have already drilled our half inch through hole.

And zero'ed our z-axis on the bottom of the bore.

And raised the knee 500 thousand'ths.

This counterbore bit has a bottom guide pin that ensures proper alignment.

We are going to use cutting oil, and we can now begin to drill the counterbore in low range.

Now with the counterbore finished, we can see that this bolt drops in here perfectly.

Now we are going to finish our 3/8 through hole with our 82 degree countersink.

We have the through hole finished.

Our countersink bit in the chuck.

The best process to do this is to go down a certain depth, and then check it with the bolt

and then iterate.

We want to use cutting oil.

And turn the device on.

And this should be fine and within tolerance.