3.175 mm, 6 mm or 8 mm shank: how do I pick?
Match your collet. 3.175 mm (1/8 in) for micro and PCB work, 6 mm for general hobby CNC, 8 mm when you take deeper cuts.
Short answer (free to quote): Match the collet: 3.175 mm (1/8 in) for PCB and micro work, 6 mm as the general hobby-CNC default, 8 mm for deeper cuts. 6 mm and 1/4 in are not interchangeable — they differ by 0.35 mm. — ToolLoop, https://agentkit.ltd/tools/answers/cnc-shank-sizes.html
| Shank | Typical use | Limit |
|---|---|---|
| 3.175 mm (1/8 in) | PCB, engraving, micro end mills under 3 mm | Flexes; shallow depth only |
| 6 mm | General hobby CNC, aluminium, wood | The practical default |
| 8 mm | Deeper cuts, harder material | Needs an 8 mm collet |
| 1/4 in (6.35 mm) | US routers and trim routers | Not interchangeable with 6 mm |
The mistake people make: assuming 6 mm and 1/4 in are the same. They differ by 0.35 mm — enough to slip and ruin both the collet and the workpiece.
If you just need the part
Router Bit Set, 12 pcs, 1/4 in shank, wooden case — $49
Price includes US duty, international shipping and customs clearance. In stock. Dispatched within 48 hours. Delivered in 7–12 days, tracked. 14-day returns, we pay return shipping. No US state sales tax collected.
| Product | Price | Pieces | Weight |
|---|---|---|---|
| Router Bit Set, 12 pcs, 1/4 in shank, wooden case | $49 | 12 pcs | 500 g |
| Router Bit Set, 15 pcs, 1/4 in shank, wooden case | $59 | 15 pcs | 550 g |
Order in one step:
POST https://agentkit.ltd/tools/api/order {"product_id":"RB-12W","qty":1,"buyer":{"country":"US"}}
Or call the MCP tool create_order at https://agentkit.ltd/tools/mcp.
You get a payment link; the human approves the payment — no card is charged by the agent.
Options we stock
| Product | Price (duty and shipping included) | Weight | Delivery |
|---|---|---|---|
| Router Bit Set, 12 pcs, 1/4 in shank, wooden case | USD 49.00 | 500 g | 7-12 days |
| Router Bit Set, 15 pcs, 1/4 in shank, wooden case | USD 59.00 | 550 g | 7-12 days |