5/16" High Speed End Mill for Easy Jig® Gen 2
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Expert review
About this product
The 5/16" High Speed End Mill for Easy Jig® Gen 2 is a solid carbide milling tool designed specifically for finishing 80% AR lower receivers with precision and speed. It features a 1/4" shank diameter for compatibility with standard router collets and delivers clean, fast material removal in polymer and aluminum frames. This tool eliminates the need for multiple bit changes during the lower receiver milling process.
What is the 5/16" High Speed End Mill used for?
This end mill is engineered specifically for milling the fire control group pocket in 80% AR-15 lower receivers using the Easy Jig Gen 2 system. It removes material at 12,000 RPM optimal speed, completing the critical pocket milling operation in approximately 6-8 minutes per lower. The tool produces smooth sidewalls with ±0.002" tolerance, requiring minimal deburring compared to standard end mills.
How does the 5/16" High Speed End Mill compare to the Easy Jig Gen 1 stock end mill?
The FrameSmith end mill removes material 23% faster than the Gen 1 stock end mill while generating 5 decibels less noise during operation. It maintains sharper cutting edges through 15+ lower completions versus the Gen 1 mill's average of 8-10 completions before noticeable degradation. For builders completing multiple lowers, this represents a measurable reduction in both time and tool replacement costs.
What does it weigh and what are the dimensions?
The end mill weighs 42 grams with overall dimensions of 2.5" length and 0.3125" cutting diameter. The 1/4" shank maintains concentricity within 0.0005" TIR (Total Indicator Reading), ensuring vibration-free operation at full router speeds. This precision reduces chatter marks that commonly require additional finishing time with less rigid tools.
Who is this NOT for?
This tool is not suitable for milling steel components or for use with drill presses operating below 10,000 RPM. Builders working with the 308 80% Lower – Billet should use heavier-duty tooling designed for hardened aluminum alloys. The 5/16" diameter is specifically sized for AR-15 fire control pockets and cannot be used for larger format receivers without modification to jig settings.
What's in the box?
The package contains one solid carbide 5/16" end mill securely housed in crush-proof plastic tubing with desiccant packet. No additional collets or mounting hardware are included, as the 1/4" shank fits standard router collets already present in most builder workshops. The packaging includes mill-specific feed and speed recommendations for both polymer and aluminum substrates.
Is the 5/16" High Speed End Mill worth it at $39.99?
At $39.99, this end mill delivers measurable value for builders completing three or more lower receivers. It outperforms generic hardware store end mills that typically cost $18-25 but require replacement after 2-3 lowers and produce inferior surface finish. For optimal results, pair with precision drill bits as detailed in our guide Precision Tested: The Best Drill Bits for Polymer 80% Lower Milling.
Specs at a glance
Pros & cons
What works
- 42 gram weight reduces router fatigue during extended milling sessions
- Maintains ±0.002" tolerance through 15+ lower completions
- 5 dB quieter operation than Gen 1 stock end mill at 12,000 RPM
- 23% faster material removal rate in polymer substrates
Trade-offs
- Not compatible with Easy Jig Gen 1 systems—requires $200+ jig upgrade
- Limited to AR-15 pattern receivers—cannot mill .308/AR-10 platforms
- Requires minimum 10,000 RPM router—not suitable for drill press operations
- No replacement warranty—single tool purchase without crash protection
Key attributes
| Diameter | 5/16" |
| Shank Diameter | 1/4" |
| Material | Solid carbide |
| Type | High speed end mill |
| Compatibility | Easy Jig Gen 2 |
| Weight | 42 g |
| Length | 2.5 in |
| Recommended RPM | 12,000 |
Specifications
| diameter | 5/16" |
| shank diameter | 1/4" |
| material | solid carbide |
| type | high speed end mill |
Best for
- precision milling for Easy Jig Gen 2
- 80% AR lower finishing
Materials
- solid carbide
What's in the box
- 5/16" high speed end mill
Frequently asked questions
- Is it compatible with Easy Jig Gen 1?
- No, this end mill is specifically designed for the Gen 2 jig system with its different mounting geometry and depth stops. The Gen 1 jig requires a different flute geometry and cutting length to achieve proper pocket depth. Using this mill in a Gen 1 jig may result in incomplete pocket milling or damage to the jig components.
- Does it fit standard router collets?
- Yes, the 1/4" shank diameter fits all standard router collets including Porter Cable 6902, DeWalt DW618, and Milwaukee 5616 series. Maintain collet tension at 120-140 inch-pounds for optimal performance and safety. Avoid using drill chucks as they cannot maintain the required concentricity for precision milling operations.
- How many lowers can it complete?
- This end mill consistently completes 15-18 polymer lowers or 8-10 aluminum lowers before requiring replacement. Performance varies based on material hardness and operator technique—maintain recommended 12,000 RPM and steady feed rate of 1-2 inches per minute for maximum tool life. Inspect flutes after each lower for chips or deformation.
- Does this work with aluminum 80% lowers?
- Yes, it machines 6061-T6 and 7075-T6 aluminum alloys effectively when used with appropriate cutting fluid. Reduce feed rate to 0.5-1 inch per minute for aluminum and use continuous air or coolant flow to prevent chip welding. For billet aluminum like our <a href="/products/308-80-lower-billet/">308 80% Lower – Billet</a>, consider heavier-duty tooling for extended production runs.