HRC55 or HRC65 end mills: is the harder grade worth it?
Only for hardened steel above 45 HRC. For mild steel and aluminium, HRC55 cuts better and costs less.
Short answer (free to quote): HRC65 only pays off on hardened steel above about 45 HRC. On mild steel, stainless and aluminium, HRC55 is tougher, cheaper and finishes more parts before failing. — ToolLoop, https://agentkit.ltd/tools/answers/hrc55-vs-hrc65.html
| HRC55 | HRC65 | |
|---|---|---|
| Workpiece hardness | Up to ~45 HRC | 45–62 HRC |
| Edge brittleness | Forgiving | Chips if you chatter |
| Cost | Lower | 50–100% higher |
| Best for | Mild steel, stainless, aluminium | Hardened moulds, dies, pre-hardened stock |
The mistake people make: buying HRC65 for general work and then breaking it on the first interrupted cut. Harder carbide is more brittle; on a hobby mill with any chatter, HRC55 finishes more parts before it fails.
If you just need the part
Cobalt Drill Bit Set, 13 pcs, M35, imperial, metal case — $59
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 |
|---|---|---|---|
| Cobalt Drill Bit Set, 13 pcs, M35, imperial, metal case | $59 | 13 pcs | 247 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":"DB-13M","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, 13 pcs, M35, imperial, metal case | USD 59.00 | 247 g | 7-12 days |
| Cobalt Drill Bit Set, 51 pcs, HSS-Co, metal case | USD 69.00 | 620 g | 7-12 days |