When installing or replacing door hinges, having the right router bit is crucial for getting clean and accurate mortises to fit the hinge leaves. With so many different types of router bits available, it can be confusing to know which one is the best choice for hinge mortises. This article will examine the most suitable router bits for cutting hinge mortises and provide recommendations on which ones work best.
Page Contents
- 1 Forstner Bits
- 2 Straight Router Bits
- 3 Upcut Spiral Router Bits
- 4 Bottom-Cleaning Router Bits
- 5 Dovetail Router Bits
- 6 Conclusion
- 7 Comparison Table of Router Bit Features
- 8 Installing Hinges in New Construction
- 8.1 Allow Proper Fitting Clearances
- 8.2 Use Appropriate Jigs
- 8.3 Cut Precisely Matched Mortises Mark and cut the matching mortise pairs in the exact same position relative to door edges. Consistent alignment is critical to proper door hanging and smooth swing clearance. Check Fit Prior to Final Hanging Test fit each hinge in its mortise without fasteners prior to hanging the door. This allows verification that the mortise openings are accurately cut before final installation. Replacing Hinges in Existing Construction When replacing hinges, the existing mortises can be reused but may require some adjustments or patching for proper fit and appearance, including: Enlarge Undersized Mortises
- 8.4 Build Up Oversize Mortises
- 8.5 Fill Old Screw Holes Fill any enlarged or misplaced screw holes from previous hinges with fitted wood plugs or toothpicks and wood glue prior to drilling pilot holes. Ensure Proper Alignment Even with existing mortises, use a marking gage to lay out and align new hinge locations to match previous operation. Tips for Accurate Router Cutting Here are some helpful tips when using a router for cutting hinge mortises: Make multiple light passes rather than one heavy pass for cleaner cuts Use a smooth, controlled feed rate for less burning Secure template or guide bushings firmly to prevent shifting Plunge router gradually to prevent bit grabbing and jumping Clear chips frequently to reduce clogging and binding Back workpiece with scrap to minimize tear-out Use sharp carbide-tipped bits for easiest cutting Troubleshooting Hinge Mortises Some common challenges and solutions when routing hinge mortises include: Hinge Binding
- 8.6 Gaps at Hinge Edges
- 8.7 Loose Fit in Jamb
- 8.8 Uneven Gaps
- 8.9 Door Slipping Off Hinges
- 9 Conclusion
Forstner Bits
One of the most common types of bits used for hinge mortises are Forstner bits. Forstner bits have a flat bottom with a beveled rim and two spurs to score the material. The flat bottom is ideal for cutting an accurate, clean mortise for the hinge leaf to sit flush in. Unlike other boring bits, Forstner bits don’t have a point at the tip so they will not penetrate further into the stock than set by the user.
Forstner bits come in a variety of sizes to match most common door hinge sizes. They are available in 1-3/8″, 1-3/4″, 2″, and 2-1/2″ diameters to accommodate 4″ and 5″ butt hinges. Matching the Forstner bit size to the hinge leaf width results in a mortise with the proper clearance.
The flat-bottomed design is the key advantage of Forstner bits for hinge mortises. They produce flat-bottom holes which allow the hinge leaf base to sit flush with the surface, rather than leaving a center point at the bottom. The clean edges also provide an excellent surface for the hinge to mate to.
Advantages of Forstner Bits
- Produce flat-bottomed mortises ideal for butt hinge leaves
- Clean sidewalls for smooth hinge function
- Precisely match common hinge sizes
- Spur scoring reduces splintering
Disadvantages of Forstner Bits
- Clean-out of waste can be difficult with deep mortises
- Bits are prone to binding in dense or wet wood
- Large size requires stable setup and handling
Straight Router Bits
Straight router bits with a bottom bearing are another excellent option for cutting hinge mortises. These are essentially elongated straight bits with a roller bearing on the bottom tip. They utilize the bearing to ride along a template pattern to guide the bit in creating a matching shape in the stock.
To create a hinge mortise, a template is made with the outline of the desired mortise size and shape. This template is clamped or secured to the workpiece. The straight bit is then adjusted to the correct depth and plunged through the template to form the mortise. The bit bearing follows the template edges to cut the proper size.
Straight bits are available with 1/4″, 3/8”, 1/2″ and wider cutting diameters to accommodate most hinge mortise widths. They typically have 1/2″ or longer cutting lengths. Carbide-tipped models provide extended edge life and clean cuts.
Advantages of Straight Bits
- Bearing rides template for highly accurate shape
- Clean sidewalls and edges
- Available in sizes to match most hinges
- Versatile for other shaping tasks
Disadvantages of Straight Bits
- Require making template for each mortise size
- Not as efficient as dedicated mortise machines
- Template must be securely attached to workpiece
Upcut Spiral Router Bits
Upcut spiral router bits are also useful for cutting hinge mortises. The upward spiraling flutes evacuate chips and sawdust up and out of deep cavities. This makes them preferred for mortises 1/2″ deep or more where chip clearance can be an issue.
Spiral upcut bits need to match the hinge width, so are available in sizes from 1/4″ to over 1/2″ diameter. Carbide-tipped models provide longevity when routing abrasive woods. The deep flutes allow these bits to plunge into the stock and create an accurate mortise in one pass.
When using a handheld router, spiral bits often produce smoother results than straight bits. The spiraling action reduces chatter for a clean finish. Their efficient chip ejection is also good for mortises cut freehand.
Advantages of Spiral Upcut Bits
- Flutes clear chips from deep cavities
- Reduce chatter for smooth sidewalls
- Plunge ability simplifies mortising
- Carrbide-tipped lasts longer in abrasive woods
Disadvantages of Spiral Upcut Bits
- Not as precise as bearing-guided straight bits
- Require light passes to reduce burning
- Can leave furry edge without template backer
Bottom-Cleaning Router Bits
Bottom-cleaning router bits are designed specifically for the task of mortise and tenon joinery. They utilize deflectors above the cutting edges to redirect chips upwards. This leaves a clean, flat bottom like a Forstner bit.
The bottom-cleaning design greatly aids hinge mortising. It evacuates waste so the base of the mortise ends up clean and ready for hinge installation. This allows the hinge leaf to fit flush without any obstruction or uneven spots.
These bits come in 1/4″, 3/8” , 1/2″ and wider diameters to suit most hinge sizes. Their cutting length ranges from 1/2″ to 1″ for typical mortise depths. Carbide-tipped models provide exceptional edge life indense woods.
Advantages of Bottom-Cleaning Bits
- Leaves flat, clean bottom surface
- Redirects chips upward and out
- Ideal for mortise and tenon joints
- Flush hinge leaf fit without adjustment
Disadvantages of Bottom-Cleaning Bits
- Relies on user skill for straight, square mortise walls
- No bearing guide like template-guided bits
- Requires steady feed rate and depth control
Dovetail Router Bits
Dovetail router bits can also be used to cut hinge mortises although they are not ideal. These bits have angled cutting edges that create dovetail-shaped cavities. For hinges, a straight bit would provide edges that allow tighter closure of the joint.
However, in a pinch a dovetail bit with the appropriate diameter for the hinge size can be used to cut a mortise. The angled shape will still allow the hinge leaf base to seat adequately in the cavity. Multiple light passes are needed to gradually clear the waste and create smooth sidewalls.
A dovetail bit’s lack of chip deflectors or bearing guide means the user must employ careful feed control. Slower passes with a dovetail bit reduce burning while allowing time to clear waste. Backing the workpiece with a template helps minimize tearout.
Advantages of Dovetail Bits
- Readily available from most bit manufacturers
- Various sizes match common hinge widths
- Allows mortising without specialized hinge bit
Disadvantages of Dovetail Bits
- Angled walls not ideal for square-cornered mortise
- No chip deflectors or bearing guide
- Prone to hinge leaf fit issues without precision
Conclusion
When selecting a router bit for cutting door hinge mortises, the proper bit for the task will result in a clean, accurate mortise installation. While various router bits can remove the waste, bits designed specifically for hinge mortising have features that simplify the process.
Forstner, bottom-cleaning, and straight router bits with bearings are best suited for producing precise mortises for flush hinge placement. Their chip clearing designs, matched sizing, and/or bearing guidance result in a quality mortise cavity.
Spiral upcut and dovetail bits can also work in a pinch but may require more skill and precision when cutting the mortise. Ultimately, by using the right router bit, you can ensure an easier mortising process and end up with perfectly fitting mortises for trouble-free door hinges.
Comparison Table of Router Bit Features
| Router Bit Type | Best Feature(s) for Hinge Mortises | Key Limitations |
|---|---|---|
| Forstner | Flat-bottom, clean sidewalls, common sizes | Waste removal, binding |
| Straight | Bearing guide, versatile sizes | Requires template |
| Upcut Spiral | Chip clearing, smooth cuts | Imprecise walls |
| Bottom-Cleaning | Flat mortise base | User skill dependent |
| Dovetail | Common availability | Angled walls |
As shown in the table, bits designed specifically for mortises offer the best performance and easier procedure for installing door hinges. While some general purpose bits can work, for clean hinge mortises, dedicated features like flat bottoms, bearings, and chip clearing make the difference.
Installing Hinges in New Construction
When installing hinges in new door construction, there are some best practices to follow with your router-cut mortises:
Allow Proper Fitting Clearances
The mortise width should exceed the hinge leaf width by 1/16″ to 1/8″ for smooth operation without binding. The mortise length should extend 1/8″ to 1/4″ past the hinge leaf to prevent the barrel from bottoming out.
Use Appropriate Jigs
For accurate alignment, use a mortising jig or hinge marking gage to lay out and center locations on doors and jambs. This ensures proper hinge placement for ideal door function.
Cut Precisely Matched Mortises
Mark and cut the matching mortise pairs in the exact same position relative to door edges. Consistent alignment is critical to proper door hanging and smooth swing clearance.
Check Fit Prior to Final Hanging
Test fit each hinge in its mortise without fasteners prior to hanging the door. This allows verification that the mortise openings are accurately cut before final installation.
Replacing Hinges in Existing Construction
When replacing hinges, the existing mortises can be reused but may require some adjustments or patching for proper fit and appearance, including:
Enlarge Undersized Mortises
If the previous hinge was slightly undersized, gently enlarge the mortise using a chisel or file until the new hinge slides in without binding.
Build Up Oversize Mortises
For loose hinge fit from oversized mortises, gluing in wood shims or applying wood filler can reduce the gap prior to installing the new hinge.
Fill Old Screw Holes
Fill any enlarged or misplaced screw holes from previous hinges with fitted wood plugs or toothpicks and wood glue prior to drilling pilot holes.
Ensure Proper Alignment
Even with existing mortises, use a marking gage to lay out and align new hinge locations to match previous operation.
Tips for Accurate Router Cutting
Here are some helpful tips when using a router for cutting hinge mortises:
- Make multiple light passes rather than one heavy pass for cleaner cuts
- Use a smooth, controlled feed rate for less burning
- Secure template or guide bushings firmly to prevent shifting
- Plunge router gradually to prevent bit grabbing and jumping
- Clear chips frequently to reduce clogging and binding
- Back workpiece with scrap to minimize tear-out
- Use sharp carbide-tipped bits for easiest cutting
Troubleshooting Hinge Mortises
Some common challenges and solutions when routing hinge mortises include:
Hinge Binding
Double check mortise width, verify bit size used, and file/sand mortise walls slightly for clearance as needed.
Gaps at Hinge Edges
Mortise may be misaligned from door edge or too wide, recut using proper template alignment.
Loose Fit in Jamb
Shim gaps in oversized mortise with wood filler, or fill and redrill screw holes as needed.
Uneven Gaps
Indicates hinge leaf not sitting flush. Check for high spots in mortise bottom, re-cut as flat as possible.
Door Slipping Off Hinges
Mortises cut too deep, allowing hinge barrel to bottom out. Maintain 1/8″ to 1/4″ gap between barrel end and mortise inner edge.
Conclusion
Cutting clean, accurate mortises is one of the most important aspects of successful hinge installation. With the right router bit, proper technique, and careful alignment, you can easily cut mortises that allow the hinges to fit flush and operate smoothly. Matching the bit size to the hinge, creating flat walls and base, and allowing just a hair of clearance will result in mortises that support the door properly on its hinges.
Test fit each hinge in its mortise without fasteners prior to hanging the door. This allows verification that the mortise openings are accurately cut before final installation.
Replacing Hinges in Existing Construction
When replacing hinges, the existing mortises can be reused but may require some adjustments or patching for proper fit and appearance, including:
Enlarge Undersized Mortises
If the previous hinge was slightly undersized, gently enlarge the mortise using a chisel or file until the new hinge slides in without binding.
Build Up Oversize Mortises
For loose hinge fit from oversized mortises, gluing in wood shims or applying wood filler can reduce the gap prior to installing the new hinge.
Fill Old Screw Holes
Fill any enlarged or misplaced screw holes from previous hinges with fitted wood plugs or toothpicks and wood glue prior to drilling pilot holes.
Ensure Proper Alignment
Even with existing mortises, use a marking gage to lay out and align new hinge locations to match previous operation.
Tips for Accurate Router Cutting
Here are some helpful tips when using a router for cutting hinge mortises:
- Make multiple light passes rather than one heavy pass for cleaner cuts
- Use a smooth, controlled feed rate for less burning
- Secure template or guide bushings firmly to prevent shifting
- Plunge router gradually to prevent bit grabbing and jumping
- Clear chips frequently to reduce clogging and binding
- Back workpiece with scrap to minimize tear-out
- Use sharp carbide-tipped bits for easiest cutting
Troubleshooting Hinge Mortises
Some common challenges and solutions when routing hinge mortises include:
Hinge Binding
Double check mortise width, verify bit size used, and file/sand mortise walls slightly for clearance as needed.
Gaps at Hinge Edges
Mortise may be misaligned from door edge or too wide, recut using proper template alignment.
Loose Fit in Jamb
Shim gaps in oversized mortise with wood filler, or fill and redrill screw holes as needed.
Uneven Gaps
Indicates hinge leaf not sitting flush. Check for high spots in mortise bottom, re-cut as flat as possible.
Door Slipping Off Hinges
Mortises cut too deep, allowing hinge barrel to bottom out. Maintain 1/8″ to 1/4″ gap between barrel end and mortise inner edge.
Conclusion
Cutting clean, accurate mortises is one of the most important aspects of successful hinge installation. With the right router bit, proper technique, and careful alignment, you can easily cut mortises that allow the hinges to fit flush and operate smoothly. Matching the bit size to the hinge, creating flat walls and base, and allowing just a hair of clearance will result in mortises that support the door properly on its hinges.
Even with existing mortises, use a marking gage to lay out and align new hinge locations to match previous operation.
Tips for Accurate Router Cutting
Here are some helpful tips when using a router for cutting hinge mortises:
- Make multiple light passes rather than one heavy pass for cleaner cuts
- Use a smooth, controlled feed rate for less burning
- Secure template or guide bushings firmly to prevent shifting
- Plunge router gradually to prevent bit grabbing and jumping
- Clear chips frequently to reduce clogging and binding
- Back workpiece with scrap to minimize tear-out
- Use sharp carbide-tipped bits for easiest cutting
Troubleshooting Hinge Mortises
Some common challenges and solutions when routing hinge mortises include:
Hinge Binding
Double check mortise width, verify bit size used, and file/sand mortise walls slightly for clearance as needed.
Gaps at Hinge Edges
Mortise may be misaligned from door edge or too wide, recut using proper template alignment.
Loose Fit in Jamb
Shim gaps in oversized mortise with wood filler, or fill and redrill screw holes as needed.
Uneven Gaps
Indicates hinge leaf not sitting flush. Check for high spots in mortise bottom, re-cut as flat as possible.
Door Slipping Off Hinges
Mortises cut too deep, allowing hinge barrel to bottom out. Maintain 1/8″ to 1/4″ gap between barrel end and mortise inner edge.
Conclusion
Cutting clean, accurate mortises is one of the most important aspects of successful hinge installation. With the right router bit, proper technique, and careful alignment, you can easily cut mortises that allow the hinges to fit flush and operate smoothly. Matching the bit size to the hinge, creating flat walls and base, and allowing just a hair of clearance will result in mortises that support the door properly on its hinges.