Carbitool
TBN4B Bull Nose Radius Router Bit with Ball Bearing Guide Carbitool
Part No: TBN4B | Barcode: 9314350007192 | Product Group: R650
The Carbitool TBN4B is a 2-flute carbide-tipped bull nose radius bit with ball bearing guide. Rounds over both edges of a board in a single pass, producing a full radiused (bull nose) profile. 4mm radius. 1/4" shank.
2 Flute
Carbide Tipped
4mm Radius
1/4" Shank
Ball Bearing Guide
Both Edges in One Pass
Compatible Materials
Hardwood
Softwood
MDF
Plywood
Laminates
Handrail Timber
Key Features & Benefits
- Full bull nose profile in one pass — rounds both the top and bottom edges of the board simultaneously, saving a second router setup.
- Ball bearing guide — tracks against the workpiece for consistent depth without a fence; suited to straight and curved work.
- Adjustable height for partial profiles — raise or lower the bit height to produce a partial radius (quarter-round) on one edge rather than the full bull nose on both.
- Drawing line bit conversion — can be modified to produce a drawing line profile; see the callout below for guidance.
- 2-flute carbide-tipped construction — long tool life and clean finish across hardwoods, softwoods and laminates.
When to Use This Bit
Choose the TBN4B for table tops, bench edges, handrails and any application needing a fully rounded (bull nose) edge profile. Adjust the machine height to use only the top half of the profile as a standard rounding over cut, or run the full depth for the classic bull nose. For a matching drawing line profile on the opposite face, pair with the Carbitool Canoe Slat Bit (TCO1B series). Radii in the R650 series run from 2 mm (TBN2B) through to 32 mm (TBN32MB 1/2).
Pro Tip: To convert the TBN4B into a drawing line bit, adjust the router height so only a portion of the cutter contacts the workpiece edge. Combined with the matching Canoe Slat Bit (TCO1B), you can produce the classic lap-join slat wall profile.
| Part No. | A (Cutting Dia.) inch | A mm | B (Cut Length) inch | B mm | B2 (Bottom) inch | B2 mm | C (Overall Length) inch | C mm | Shank inch | Shank mm | Barcode |
|---|---|---|---|---|---|---|---|---|---|---|---|
| TBN2B | 25/32 | 19.84 | 1/2 | 12.70 | 5/32 | 3.97 | 2 | 50.80 | 1/4 | 6.35 | 9314350007154 |
| TBN2B 1/2 | 25/32 | 19.84 | 1/2 | 12.70 | 5/32 | 3.97 | 2-1/2 | 63.50 | 1/2 | 12.70 | 9314350007161 |
| TBN4.5MB 1/2 | — | 20.40 | 1/2 | 12.70 | 11/64 | 4.37 | 2-1/2 | 63.50 | 1/2 | 12.70 | 9314350014329 |
| TBN5MB 1/2 | — | 20.90 | 1/2 | 12.70 | 13/64 | 5.16 | 2-1/2 | 63.50 | 1/2 | 12.70 | 9314350014961 |
| TBN3B | 27/32 | 21.43 | 1/2 | 12.70 | 7/32 | 5.56 | 2 | 50.80 | 1/4 | 6.35 | 9314350007178 |
| TBN3B 1/2 | 27/32 | 21.43 | 1/2 | 12.70 | 7/32 | 5.56 | 2-1/2 | 63.50 | 1/2 | 12.70 | 9314350007185 |
| TBN4B ★ | 29/32 | 23.01 | 3/4 | 19.05 | 9/32 | 7.14 | 2-3/8 | 60.33 | 1/4 | 6.35 | 9314350007192 |
| TBN4B 1/2 | 29/32 | 23.01 | 3/4 | 19.05 | 9/32 | 7.14 | 2-3/4 | 69.85 | 1/2 | 12.70 | 9314350007208 |
| TBN6B | 1-1/32 | 26.19 | 3/4 | 19.05 | 13/32 | 10.32 | 2-3/8 | 60.33 | 1/4 | 6.35 | 9314350007215 |
| TBN6B 1/2 | 1-1/32 | 26.19 | 3/4 | 19.05 | 13/32 | 10.32 | 2-3/4 | 69.85 | 1/2 | 12.70 | 9314350007222 |
| TBN8B 1/2 | 1-5/32 | 29.37 | 1 | 25.40 | 17/32 | 13.49 | 3 | 76.20 | 1/2 | 12.70 | 9314350007239 |
| TBN10B 1/2 | 1-9/32 | 32.54 | 1-3/32 | 27.78 | 21/32 | 18.26 | 3-1/4 | 82.55 | 1/2 | 12.70 | 9314350007246 |
| TBN12B 1/2 | 1-13/32 | 35.72 | 1-1/4 | 31.75 | 25/32 | 19.84 | 3-1/4 | 82.55 | 1/2 | 12.70 | 9314350007253 |
| TBN15B 1/2 | 1-21/32 | 42.07 | 1-1/2 | 38.10 | 1-1/32 | 26.19 | 3-5/8 | 92.08 | 1/2 | 12.70 | 9314350007260 |
| TBN32MB 1/2 | 1-57/64 | 48.02 | 1-39/64 | 40.88 | 1-17/64 | 32.15 | 3-7/8 | 98.43 | 1/2 | 12.70 | 9314350014954 |
★ You are viewing the highlighted variant. Other sizes in this series are also available.
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