The correct hole saw size for a 1 1/2 inch EMT connector is 1 9/16 inches. This size ensures a snug, secure fit for the conduit when passing through junction boxes, enclosures, or panels.
When working with electrical conduit, precision matters a great deal. Getting the hole size wrong can lead to loose connections, exposed wires, or difficulty in installation. This guide will help you choose the right tools and methods for cleanly cutting holes for 1 1/2 inch Electrical Metallic Tubing (EMT) connectors.
Image Source: shieldenstrut.com
Choosing the Right Tool: Hole Saw vs. Knockout Punch
Electricians often face a choice when making openings in metal enclosures: use a hole saw or a knockout punch. Both tools have their place, but for certain jobs, one is much better than the other.
Knockout Punch for EMT Fittings
A knockout punch is designed specifically for this job. It creates a precise hole that exactly matches the size needed for the fitting.
For a 1 1/2 inch EMT connector, the required knockout size is standardized. This ensures code compliance and a perfect fit.
- Pros of Knockout Punches: They create a very clean, burr-free hole. They are fast once set up.
- Cons of Knockout Punches: They require heavy-duty tools, often hydraulic ones for larger sizes. They can be expensive for occasional use.
Hole Saws for EMT Fitting
A hole saw is a more common and versatile tool found in many toolboxes. It uses a circular cutting blade mounted on an arbor.
When looking for the hole saw size for 1.5 inch EMT, remember that the trade size (1 1/2 inch) does not always match the actual hole diameter needed. Electrical standards dictate the necessary opening.
| Trade Size | Required Knockout Diameter (Inches) | Recommended Hole Saw Size (Inches) |
|---|---|---|
| 1/2″ EMT | 7/8″ | 7/8″ or 1″ |
| 3/4″ EMT | 1 1/8″ | 1 1/8″ |
| 1″ EMT | 1 3/8″ | 1 3/8″ |
| 1 1/2″ EMT | 1 11/16″ | 1 9/16″ or 1 5/8″ |
| 2″ EMT | 2 1/16″ | 2 1/16″ |
Note: Standards can vary slightly by enclosure manufacturer and local codes. Always verify the specific knockout size for 1 1/2 EMT connector if possible.
The EMT connector hole saw diameter should aim to be slightly smaller than the full hole required by a standard knockout die, especially for compression fittings, to ensure the connector grips the metal panel firmly. This is why 1 9/16″ is the common choice over a perfect 1 11/16″.
Deciphering the Correct Hole Saw Size for 1.5 Inch EMT
Why isn’t the hole saw exactly 1.5 inches? This is a common point of confusion in conduit work. Conduit trade sizes do not equal the hole size needed for installation.
Trade Size vs. Actual Diameter
EMT conduit is sized by its nominal trade size. A 1 1/2 inch EMT conduit has an actual outside diameter (OD) of about 1.900 inches. However, the connector is designed to fit the opening in the electrical box, not the conduit OD directly.
For the locking setscrew or compression type of 1 1/2 inch EMT connector:
- The hole must be large enough for the body of the connector to pass through.
- The hole must be small enough for the retaining ring or threads of the connector to grip the panel securely.
This balance dictates the 1.5 inch conduit hole saw specification. Most manufacturers specify a hole diameter of 1 11/16 inches (1.6875 inches) for a standard 1 1/2 inch trade size knockout.
When using a hole saw, slightly undercutting this dimension is often preferred to avoid excessive play. Therefore, a 1 9/16 inch hole saw is the practical answer for the hole saw size for 1.5 inch EMT. If the hole is too big, the fitting won’t seat properly, increasing the risk of pull-out or poor grounding continuity.
Impact of Connector Type
The best hole saw for EMT fitting can depend slightly on the type of connector you use:
- Compression Fittings: These rely on squeezing the conduit within the fitting body. A slightly smaller hole is acceptable, sometimes even preferred, as the compression action will hold it.
- Set Screw Fittings: These use a screw to lock onto the conduit. The panel hole size is more critical here for proper seating of the coupling body.
When cutting hole for 1 1/2 inch rigid connector (which shares similar sizing requirements to EMT fittings in this context), precision remains paramount.
Step-by-Step Guide: Drilling the Hole
Knowing the size is the first step. Executing a clean, safe cut is the next. This process applies whether you are working on a thin steel box or a thick enclosure door.
Safety First
Always prioritize safety when drilling metal.
- Wear safety glasses. Metal shards can fly off quickly.
- Use insulated gloves, especially if the enclosure might be energized (though this work should generally be done when power is off).
- Ensure the work piece is clamped down securely.
Preparing for Drilling
- Locate the Center: Mark the exact center point where the conduit needs to enter the enclosure.
- Center Punch: Use a sharp center punch to create a small divot. This stops the hole saw from “walking” across the smooth metal surface when you start drilling.
Selecting and Mounting the Hole Saw
You need a high-quality hole saw designed for metal cutting.
- Material: Look for bi-metal hole saws. They are durable and can handle the heat generated when cutting steel or thick metal. Carbide-tipped saws are even better for heavy-duty work on stainless steel or very thick conduit bodies but might be overkill for standard junction boxes.
- Arbor and Pilot Bit: Ensure your hole saw is mounted securely on the correct arbor. The pilot drill bit in the center of the saw guides the cut. Make sure it is sharp.
The Drilling Process
Drilling metal requires patience and lubrication, not brute force.
Applying Lubrication
Lubrication is essential to prolong the life of your hole saw and achieve a better cut.
- Use cutting oil or heavy-duty grease on the edge of the saw.
- Do not use water unless the saw is specifically designed for it, as water can promote rust on standard bi-metal saws.
Starting the Cut
- Start the drill at a slow to medium speed.
- Apply gentle, steady pressure. Let the teeth do the work. Forcing the saw will overheat it, dulling the teeth instantly.
- Once the pilot bit breaks through the other side, you can increase the speed slightly, but maintain light pressure.
If you are drilling through very thick material (like a heavy floor stand), consider using a knockout punch vs hole saw for EMT debate here: A hydraulic punch will be vastly faster and cleaner in very thick material over 1/8 inch.
Finishing the Cut
As the saw nears the end of the material, reduce pressure significantly. If you push too hard, the saw can suddenly break through, causing the saw to bind or the material to shift violently.
Finishing Touches
After the hole is cut, clean up the edges.
- Deburring: Use a file, a specialized deburring tool, or a rotary tool with a grinding bit to smooth the inside and outside edges of the hole. This is critical. Burrs can damage wire insulation as you pull the conductors through.
- Inspection: Check the hole size against your hole saw chart for electrical fittings one last time. The 1 1/2 inch EMT connector should slide in firmly with a slight push or tap.
Optimizing Tool Choice: The Best Hole Saw for EMT Fitting
Selecting the right equipment directly affects the speed and quality of your electrical installations. For routine work involving 1 1/2 inch EMT, investing in the right hole saw makes a difference.
Portable Drill vs. Magnetic Drill Press
The method of drilling greatly impacts the result.
- Handheld Corded/Cordless Drill: Excellent for quick jobs, small quantities, or when working high up on a ladder. Control is entirely up to the user. You must be very steady to maintain the correct angle and pressure.
- Magnetic Drill Press (Mag Drill): Ideal for production environments or when drilling into large panels or structural steel. The magnetic base locks the drill steady, ensuring a perfectly perpendicular hole and consistent pressure. This is the superior method for achieving the precise EMT connector hole saw diameter repeatedly.
Blade Longevity and Speed
When dealing with 1 1/2 inch conduit fittings, you will likely be cutting through galvanized steel enclosures.
| Blade Type | Best Use Case | Typical Life (Cuts on 16ga Steel) | Cost |
|---|---|---|---|
| High-Speed Steel (HSS) | Occasional, light gauge metal | 5 – 10 | Low |
| Bi-Metal | Standard professional use, varied thickness | 20 – 50 | Medium |
| Carbide Tipped | Heavy steel, production work | 100+ | High |
For most electricians, a good quality bi-metal saw marked clearly for metal use will provide the best balance of cost and performance when creating openings for securing EMT conduit.
Practical Application: Securing 1 1/2 Inch EMT Conduit
The reason we obsess over the exact hole saw size for securing EMT conduit is directly related to how these fittings work.
A 1 1/2 inch EMT connector is designed to connect the conduit to a junction box or enclosure. The main body of the connector passes through the hole you drill. A retaining nut (or sometimes a built-in lip or compression ring) tightens against the outside surface of the enclosure panel.
If the hole is too large:
- The connector cannot achieve proper torque on the retaining nut.
- The connector might pull back under tension, creating a gap.
- If it’s a compression fitting, the grip might not be tight enough, leading to vibration failure or poor electrical contact if grounding continuity relies on that connection.
If the hole is slightly too small (e.g., using a 1 1/2 inch hole saw when 1 11/16 inch is needed):
- The connector body will get stuck halfway through.
- You will waste time filing or grinding the opening larger. This defeats the purpose of using a precise tool like a hole saw in the first place.
This confirms why targeting the standard knockout size for 1 1/2 EMT connector (which is slightly less than 1 11/16 inches for the hole saw approach) is the best practice. The 1 9/16 inch saw provides the best compromise for a fast, clean cut that still allows the fitting to seat securely.
Comparison: Hole Saw vs. Knockout Punch for Larger Runs
While the hole saw is convenient, it’s important to contrast it with the professional standard for high-volume work.
When to Use a Knockout Punch
If you are installing conduit throughout a large commercial building or facility, using a knockout punch vs hole saw for EMT comparison heavily favors the punch.
A hydraulic knockout punch offers superior speed and precision for repetitive work on panel enclosures. It creates a smooth opening with virtually no burrs, which is ideal when installing dozens of 1 1/2 inch conduit runs.
When a Hole Saw Excels
The hole saw shines in retrofit situations or low-volume tasks:
- When you need to add a single box or access point to an existing wall or structure.
- When working with junction boxes that are already mounted and cannot easily support the pressure of a knockout punch being driven through them.
- When the material is too thick or too irregularly shaped for a standard punch setup.
For anyone needing the definitive hole saw size for 1.5 inch EMT, sticking to 1 9/16″ will cover the vast majority of standard installations using compression or set-screw fittings designed for 1 1/2″ trade size EMT.
Further Considerations for Metal Drilling
Drilling Through Multiple Layers
If you are drilling hole for 1 1/2 EMT conduit through stacked metal sheets (like double-walled enclosures or framing), you must adjust your technique.
- Pilot Hole Check: Drill the pilot bit through all layers first to ensure alignment.
- Lubrication Intervals: Pause frequently during the cut, backing the saw out slightly to clear chips and reapply cutting oil.
- Support: Ensure the material behind the initial cut is firmly supported so it doesn’t collapse inward when the saw breaks through.
Interpreting the Hole Saw Chart for Electrical Fittings
Electrical codes and fitting guides provide charts to standardize these openings. Always reference the chart for the specific fitting brand if possible, but the industry standard approximations listed earlier generally hold true.
For example, a general hole saw chart for electrical fittings confirms that for a 1 1/2″ fitting, the required hole diameter centers around 1.56 to 1.69 inches. Choosing 1 9/16 inches (1.5625 inches) sits perfectly within that acceptable range for most common compression fittings.
Maintaining Your Tools
Proper tool care ensures you can always rely on your equipment for accurate cuts.
- Cleaning: After every use, clean the hole saw teeth of all metal shavings and old cutting oil residue.
- Storage: Store saws flat or in a dedicated case to protect the teeth and the pilot bit. Never store them loose where they can knock against other metal tools.
- Sharpening: If the saw begins to struggle, you can sharpen the teeth using a fine-grit metal file or a specialized grinding bit on a rotary tool. Only sharpen the cutting edge of each tooth.
By paying attention to these details—especially selecting the appropriate EMT connector hole saw diameter—you ensure a professional, code-compliant, and safe electrical installation every time you are drilling hole for 1 1/2 EMT conduit.
Frequently Asked Questions (FAQ)
Q: Can I use a 1 5/8 inch hole saw for 1 1/2 inch EMT connector?
A: Yes, a 1 5/8 inch hole saw (1.625 inches) is often acceptable. Since the standard knockout dimension is 1 11/16 inches (1.6875 inches), 1 5/8 inches is slightly smaller but generally still allows the fitting to seat securely. Many professionals opt for this size if 1 9/16 inches is unavailable, as it reduces the risk of filing later.
Q: Is a 1 1/2 inch hole saw too small for 1 1/2 inch EMT connector?
A: Yes, a 1 1/2 inch hole saw (1.500 inches) is definitely too small. A 1 1/2 inch EMT connector body is slightly larger than 1.5 inches in diameter, and the fitting needs clearance to pass through the panel surface completely before the retaining mechanism tightens. This hole will likely bind the connector or prevent it from seating fully.
Q: Do I need a special hole saw size for 1 1/2 inch Rigid Connector instead of EMT?
A: For the 1 1/2 inch trade size, the required hole size for Rigid conduit connectors is often identical to EMT fittings because they must fit the same standard knockout size in the enclosure panel. Therefore, the hole saw size for securing EMT conduit (1 9/16″) generally applies to rigid connectors as well.
Q: Should I use a knockout punch or a hole saw for 1 1/2 inch fittings?
A: For multiple, clean holes in new panels, a hydraulic knockout punch is faster and creates a superior, burr-free edge. For occasional use, repairs, or tight spots, a hole saw is more convenient and portable.