What’s actually slowing this PC down?
Pick the symptom - the matching free tool is one click away.
Bird’s-mouth router bits cut interlocking profiles in the edges of staves for polygonal projects such as hollow columns, planters, bowls, and boxes. Choose a cutter made for the number of sides and stock thickness you plan to use, verify its shank fits your router, and follow the exact model’s router-table instructions. These bits are not for cutting the birdsmouth notch used where a roof rafter bears on a wall.
What a bird’s-mouth router bit does
A bird’s-mouth bit machines a profiled edge on one side of each stave. When the pieces are brought together, their edges nest to form a multi-sided assembly. Lee Valley describes the joint’s historical use in wooden boat masts and booms, as well as its use for six-, eight-, twelve-, or sixteen-sided hollow forms. Trend describes similar cutters for round boxes, planters, barrels, and other multi-sided components.
As an Amazon Associate I earn from qualifying purchases.
The assembled piece can remain faceted or be planed or sanded round after the glue has dried. Lee Valley says the nesting edges make glue-up easier by helping the pieces resist shifting; Trend says the notch creates a larger gluing area. These are the manufacturers’ descriptions, not independent comparative tests of joint strength.
PC Slower Than It Used to Be?
A free scan shows the junk files, broken settings and background clutter dragging Windows down - then fixes them in one click.Free scan · Windows 10 & 11Outdated Drivers Are Slowing You Down
One free scan finds every outdated or missing driver and matches the right update for your exact hardware.Free scan · exact hardware matchChoose a cutter for the project
Match the number of sides
Start with the finished shape and its side count. Lee Valley lists cutters for 6/12-sided, 8-sided, and 16-sided work. Trend lists a 6/12-sided cutter and a separate 8-sided cutter. A cutter intended for one configuration should not be assumed to work for another: use the maker’s chart and instructions for the exact model.
#1 Best Overall
- This Birdsmouth Router bit will cut stock up to 1-1/8" thick to make 12 sided objects and up to 3/4" to make 6 sided objects. The shank is 1/2".
- Create multi-sided polygon objects such as barrels and planters with precise angles and lots of gluing surface
- Premium C3 micro-grain tungsten carbide blades for a sharper & longer lasting edge
- For use on table mount router only
- Silver induction brazing for maximum strength and durability
Check stock thickness and setup orientation
Maximum stock thickness and workpiece orientation vary by model. The specifications below are for the cited products only; they are not general limits for all bird’s-mouth bits.
| Product or configuration | Published stock specification | Published orientation |
|---|---|---|
| Lee Valley bird’s-mouth joinery bits | Up to 7/8 inch material for flush joints; thicker stock may need dressing after glue-up. | Check the instructions for the selected cutter. |
| Trend 6/12-sided cutter, 6-sided setup | 20 mm maximum. | Cut face side up. |
| Trend 6/12-sided cutter, 12-sided setup | 12 mm maximum. | Cut face side down. |
| Trend 8-sided cutter | 20 mm maximum. | Cut face side up. |
Do not transfer a thickness limit or orientation from one cutter to another. Also compare the selected model’s diameter, cutting length, and setup dimensions with your project; the figures are specific to each product.
Rank #2
- This Birdsmouth Router bit will cut stock up to 1" thick to make 8 sided objects. The shank is 1/2".
- Create multi-sided polygon objects such as barrels and planters with precise angles and lots of gluing surface
- Premium C3 micro-grain tungsten carbide blades for a sharper & longer lasting edge
- For use on table mount router only
- Silver induction brazing for maximum strength and durability
Confirm shank and router compatibility
The cited Lee Valley and Trend cutters specify a 1/2-inch shank. Check the shank size on the exact bit and confirm that your router’s collet accepts it. A matching shank alone does not establish that a cutter is suitable for a particular router or setup; follow the cutter maker’s instructions.
Set up and use the bit safely
Use the specified router-table arrangement
Lee Valley says its bits should be used only in a router table equipped with a fence, not freehand. Follow that restriction for those cutters. For other models, consult their instructions rather than assuming that a different setup is acceptable.
Rank #3
- EASY MULTI-SIDED PROJECTS: Our multi-sided woodworking router bits the process of joining up multi-sided projects, making it incredibly easy. Say goodbye to complicated angles and hello to seamless assembly
- VERSATILE APPLICATION: Suitable for use with solid wood, hardwood, chipboard, and more, our glue joint bits are versatile and adaptable to various materials. From simple DIY projects to professional woodworking tasks, these bits are the companion for all your joining needs
- STRONG AND EFFICIENT DESIGN: Designed to cut at the correct angle, our router bits provide additional gluing area and create a sturdy mechanical joint. Enjoy peace of mind knowing your projects are securely joined with strength and
- ROBUST CARBIDE BLADE: With a carbide blade that offers increased strength and minimal resistance, our trimming router bits ensure efficient and cutting. Experience smooth and hasslefree handlings every time
- CUSTOMIZED CUTS FOR YOUR PROJECT: Choose the desired bit and cut according to the number of sides needed for your project. Enjoy the flexibility of customizing your cuts to meet the requirements of each project you undertake
Make a test cut before machining project stock
- Read the instructions for the exact cutter and configure the router table, fence, and workpiece orientation as specified.
- Use scrap that matches the project stock in thickness and material. The Yonico 15138 instructions for its 8-sided cutter recommend a test cut to check the fit; its setup calculations are specific to that model.
- Check how the test pieces meet before routing the full set of staves. If the fit or setup is wrong, adjust according to the cutter’s instructions and test again.
- Feed the workpiece in a controlled manner and use the safety devices specified by the maker. Yonico’s instructions describe using a push stick to keep hands away from the cutter; follow the safety guidance for your own model and router-table setup.
Do not confuse router-bit joinery with a rafter birdsmouth
“Bird’s-mouth bit” can refer to a router cutter for joining staves in a polygonal object. A rafter birdsmouth is a notch cut in framing lumber where a roof rafter bears on a wall. The router cutter described here is for edge profiling in multi-sided assemblies; it is not a rafter-cutting tool, and this article does not provide roof-framing dimensions or structural guidance.
Quick Recap
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
