Product Description
The CMT 799.164.00 Reduction Bushing (1/4" - 3/8") is a precision-ground steel adapter designed to reduce bearing and collet bore sizes, giving router users a reliable way to match tooling to the correct shaft or bearing diameter. Built from solid steel and machined to tight tolerances, this compact bushing eliminates wobble during operation and ensures accurate, repeatable tool positioning - whether you are fitting a bearing onto a router bit or adapting a collet to a smaller shank size.
Key Features
- Reduction bushing for bearings - adapts CMT router bit bearings and collet bores to smaller shaft diameters, expanding the range of tooling configurations you can run without purchasing separate bit sets.
- Precision-ground steel construction - tight machining tolerances mean the bushing seats firmly with no play or wobble, protecting both the bearing and the workpiece from inaccurate cuts.
- 3/8" outer diameter with 6.35mm (1/4") bore - the specific sizing bridges a common gap between 3/8" bearing IDs and 1/4" shank diameters, making this a practical everyday adapter for router tables and handheld routers alike.
- 25mm total length - provides sufficient contact area between the bushing and the bearing or collet bore, distributing load evenly and reducing wear over repeated use.
Why This Product
- When a router bit bearing has a 3/8" bore but your shank or pilot measures 1/4" (6.35mm), this bushing fills that gap exactly - no shimming, no improvising, and no risk of a loose-fitting bearing damaging the workpiece or bit.
- Precision-ground steel holds its shape under the rotational stress of router operation, so the bushing remains a snug, concentric fit through repeated tool changes and extended production runs.
- At 25mm in total length, the bushing offers stable, full-contact engagement inside the bearing bore - a longer contact surface compared to thin shim-style adapters that can tilt or shift under load.
- Because this is a dedicated reduction bushing rather than a workaround, it keeps your router bit assembly properly aligned, which translates directly to cleaner profiles, consistent edge quality, and reduced tearout on the workpiece.
Specifications
- Manufacturer Part Number: 799.164.00
- Brand: CMT Orange Tools
- Product Type: Reduction Bushing
- Diameter: 3/8"
- Bore Diameter: 6.35mm
- Total Length: 25mm
- Material: Steel
Approved Applications
- Adapting bearing and collet bore sizes on router bits and router tooling
- Compatible with CMT router bits and related tooling systems
- Suitable for use with handheld routers and router tables
Frequently Asked Questions
What does this bushing actually do - and when do I need it?
This is a reduction bushing that fits inside a 3/8" bearing bore and reduces the opening to accept a 1/4" (6.35mm) shaft or pilot. You need it when a router bit bearing has a 3/8" inner diameter but the shank or pilot it needs to ride on measures 1/4" - without the bushing, the bearing would have too much play and could shift during the cut.
Will this bushing fit bearings from other manufacturers, or is it CMT-specific?
The bushing is sized to standard dimensions - 3/8" outer diameter and 6.35mm bore - so it can physically fit any bearing with a matching 3/8" inner diameter. However, the product data identifies it as a reduction bushing for CMT bearing and collet applications, so compatibility with non-CMT tooling should be verified against your specific bearing dimensions.
Is the 6.35mm bore the same as a standard 1/4" shank?
Yes. 6.35mm is the metric equivalent of exactly 1/4", which is one of the most common router bit shank sizes. This bushing is designed to bridge that 1/4"-to-3/8" size difference precisely, which is why it is labeled as a 1/4" - 3/8" bushing.
Why is the 25mm length significant for a bushing this small?
A longer bushing provides more contact surface between the bushing and the bearing bore, which keeps the assembly centered and resistant to tilting under load. The 25mm total length ensures stable, wobble-free engagement rather than the point-contact you would get from a much shorter or thinner adapter.
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