How to Evaluate Carbide Grades for Your Machining: A Buyer's 5-Step Checklist

Who This Checklist Is For

If you're a manufacturing engineer or procurement professional evaluating cutting tool materials—specifically Kennametal carbide grades—this is for you. You're likely comparing options for a new part program, trying to reduce tooling spend, or standardizing across multiple machines. The goal here isn't theory. It's a repeatable process you can use next time you're sitting down with a catalog or a supplier quote.

I'm a procurement manager at a mid-sized aerospace components manufacturer. I've managed our cutting tools budget (roughly $180,000 annually) for six years, negotiated with 12+ vendors, and documented every order in our cost tracking system. This checklist comes from what I've learned the hard way.

The 5-Step Checklist for Evaluating Carbide Grades

Step 1: Start with the Material Group and ISO Code

Before you even look at a specific grade, you need to know what you're cutting. Sounds obvious, right? But I've seen engineers skip this step and jump straight to 'I need the hardest grade you've got.' That's how you end up with chipping or premature wear.

Kennametal's grades are designed around the ISO material groups:

• P class – steel (most common in automotive and general machining)
• M class – stainless steel (aerospace, medical)
• K class – cast iron (heavy equipment, mining)
• N class – non-ferrous (aluminum, titanium)
• S class – superalloys (jet engines, high-temp applications)
• H class – hardened steel (molds, dies)

Checkpoint: Write down the specific material and its hardness (Rc or HB). Without this, you're guessing. I keep a spreadsheet with our common jobs—AISI 4140 at 28-32 Rc, 304 stainless at 200 HB—so I can cross-reference immediately.

Step 2: Match the Application Type—Continuous vs. Interrupted Cut

This is where most people miss the mark. A grade that performs flawlessly in a continuous turning operation (like a shaft) might fail instantly in an interrupted cut (like a keyway or roughing with scale). I learned this the hard way when I recommended a high-hardness grade for a roughing operation. Chipped within 10 parts. Total cost: new insert, downtime, rework—easily $400.

Kennametal's catalog usually categorizes grades by application:

• Continuous – smooth surfaces, stable conditions → look for higher hardness/wear resistance (e.g., KC5010 coating on a P20-P30 grade)
• Interrupted – uneven surfaces, variable load → look for higher toughness (e.g., KC5025 or a grade with more cobalt binder)
• General purpose – moderate conditions → a balance (e.g., KC9110)

Checkpoint: On your job card, mark 'continuous,' 'interrupted,' or 'mixed.' Then filter grades that match. A common mistake is using a single grade for everything. That's where the hidden costs pile up.

Step 3: Check the Coating—It's Not Just a 'Nice to Have'

When I compared KC5010 and KC5025 side by side on the same P20 steel job (same parameters, same operation), I finally understood why coating matters so much. The KC5010—a CVD-coated grade with high aluminum content—gave me 40% more tool life. That's not a typo. The coating directly affects thermal stability and wear resistance.

Kennametal uses several coating families:

• CVD (chemical vapor deposition) – thick, good for wear resistance at high speeds. Examples: KC5010, KC5025.
• PVD (physical vapor deposition) – thinner, sharper edge, good for finishing. Examples: KC5510, KC5525.
• Advanced coatings – multi-layer, designed for specific alloys. Examples: TMC (toughness)+, DuraTec.

Checkpoint: Ask your supplier for the coating type and its intended application. If you're running high-speed finishing on steel, don't use a PVD coating meant for interrupted cuts. Sounds simple, but I've received wrong recommendations twice in the past year—each time costing us a week of trial-and-error.

Step 4: Calculate Total Cost of Ownership (TCO) Using Performance Data

Here's where the cost controller in me kicks in. The purchase price of an insert is only the tip of the iceberg. The real cost includes:

• Tool life – how many parts per edge
• Cycle time – feeds and speeds you can achieve
• Changeover time – downtime to replace inserts
• Scrap/rework rate – parts with poor finish due to wear

Template I use (honestly): 'Cost per part = (insert price / total edges) + (labor rate × changeover time / parts per changeover) + scrap cost.'

I've seen a grade that cost $12 per insert but gave 800 parts per edge, vs. a $8 grade that gave 200 parts. The $12 grade saved me $0.02 per part—and over 10,000 parts, that's $200 plus reduced downtime. The 'cheap' option resulted in a $1,200 redo when quality failed.

Checkpoint: Ask the supplier for documented performance data (speed, feed, tool life) for your specific material. If they can't provide it, that's a red flag. Kennametal's application engineers usually have this data from their mills—I've used it to justify switching grades to my CFO.

Step 5: Test, Then Standardize (The Step Most People Skip)

I knew I should run a test before standardizing a new grade across all our CNC cells. But I thought, 'We've been doing this for years—what are the odds it'll fail?' The odds caught up with me when a 'universal' grade chipped on a keyway operation. That was the one time it mattered.

My protocol:

1. Select one job with moderate material and average parameters.
2. Compare the new grade side-by-side with your current one (same tool path, same operator).
3. Measure edge wear after defined number of parts (e.g., 100 for steel).
4. Run at least 3 repeats to account for material variation.
5. Document results—don't rely on memory. I track this in our ERP system.

Checkpoint: Only standardize after you have 3 consistent tests. Anything less is a gamble. The lean guy in me says: 'One good test beats ten supplier specs.'

Common Mistakes to Avoid

Mistake 1: Ignoring the Binder Content

A higher cobalt binder percentage means more toughness but lower wear resistance. This was true 20 years ago when carbide technology was simpler. Today, advanced coating technologies like KC5010 have largely closed that gap in many applications—but 'largely' isn't 'completely.' For heavy roughing, a high-toughness grade (like KC5025 with ~10% cobalt) still beats a high-wear grade with 6% cobalt.

Mistake 2: Buying on Price Alone

The 'savings' from a cheaper insert disappear fast if you change inserts twice as often. Seen it happen. A $2 difference per insert can cost you $5 in labor and downtime per change. Over a year, that adds up.

Mistake 3: Forgetting About Chip Control

I compared our rush orders (non-standard chipbreaker designs) vs. standard grades over a full year. We were spending 40% more on artificial emergencies because we didn't stock the right chipbreaker for a new job. The cost wasn't just the tool—it was the logistic chaos. The standard grade's chipbreaker (like the M5 or TF for steel) should be your baseline before you customize.

That checklist has saved me from two major cost overruns in the past 18 months and helped me justify a switch to Kennametal's KC5010 for our steel jobs—a move that cut our per-part cost by 17% when we accounted for tool life and reduced rework. It's not flashy. It works.