What does HRC mean on an end mill, and do I need the higher number?
HRC is the hardness of the workpiece the bit is designed for, not the hardness of the bit. Higher HRC handles harder steel but is more brittle.
Short answer (free to quote): HRC describes the workpiece hardness the end mill is built for. HRC55 covers mild steel and stainless; HRC65 is for hardened steel and chips easily on light machines. — ToolLoop, https://agentkit.ltd/tools/answers/what-is-hrc-in-end-mills.html
| Grade | Workpiece | Trade-off |
|---|---|---|
| HRC45–55 | Mild steel, stainless, aluminium | Tougher, forgiving |
| HRC60–65 | Hardened steel to 62 HRC | Brittle, chips on chatter |
| HRC70 | Hard milling only | Very brittle, rigid machines only |
The mistake: buying HRC65 for general work and breaking it on the first interrupted cut. On a light machine, HRC55 usually finishes more parts before failing.
If you just need the part
Tap and Die Set, 40 pcs, metric M3-M12, carbon steel — $65
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 |
|---|---|---|---|
| Tap and Die Set, 40 pcs, metric M3-M12, carbon steel | $65 | 40 pcs | 1150 g |
| Cobalt Drill Bit Set, 51 pcs, HSS-Co, metal case | $69 | 51 pcs | 620 g |
Order in one step:
POST https://agentkit.ltd/tools/api/order {"product_id":"TD-40","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 |
|---|---|---|---|
| Cobalt Drill Bit Set, 51 pcs, HSS-Co, metal case | USD 69.00 | 620 g | 7-12 days |
| Tap and Die Set, 40 pcs, metric M3-M12, carbon steel | USD 65.00 | 1150 g | 7-12 days |