Kennametal Insert Grades Chart: How to Read It When Your Machine, Customer, or Plant Changes the Answer

For the past seven years, I have handled cutting tool orders for a shop that does both job-shop machining and energy-industry repair work. I have personally made and documented eleven significant insert-ordering mistakes. Maybe ten, since I might be double-counting one chipbreaker issue. The total waste was roughly $4,300 in tooling, scrap parts, and emergency freight. Now I maintain our team's insert-selection checklist so we don't repeat those errors.

The lesson was not that I was lazy. The lesson was that I treated the Kennametal insert grades chart as one universal ranking table. It isn't. The chart only becomes useful after you answer one question: which scenario are you in?

There Is No Universal 'Best' Row on the Chart

For years I searched for the one grade that would cover every job in our shop. There isn't one. A Kennametal insert may be excellent in finishing steel but too brittle for an interrupted cast iron cut. Another grade may work great in rigid equipment but fail on an older machine with chatter and low coolant pressure.

The same logic applies to the search phrase 'Kennametal inserts grades chart.' If you ask that question from a clean engineering office, you probably need one type of answer. If you ask it from a tool crib next to a 2001 CNC, you need another. That is not an excuse. It is the reason the chart is organized by conditions, not by a simple score.

Scenario A: You Are Starting From Scratch for a New Job

If you are picking a grade for a new part and there is no previous tooling history, start by narrowing the chart using four things:

• Work material group. Steel, stainless, cast iron, non-ferrous, high-temp alloy, or hardened material?
• Operation type. Are you turning, milling, boring, or drilling? Some charts blend grades across operations, but your edge geometry and coolant delivery are not the same.
• Surface condition. Is the cut continuous or interrupted? Is there scale, a weld, or a forged skin?
• Rigidity. Are you on a stiff machining center or a lighter manual machine? The same grade can look brilliant in one situation and terrible in another.

I remember comparing two Kennametal insert grades side by side on the same material. On paper, the harder CVD-coated grade promised better wear life. In our shop, it chipped within minutes because the cut had a slight interruption and our setup was not as rigid as the test lab's setup. The tougher grade lasted longer and left a better finish. That contrast is what finally made me understand the chart: I was not looking for the best grade; I was looking for the row that matched our conditions.

Scenario B: The Drawing Already Specifies Kennametal Orwell Ohio

Sometimes the question is not about grade performance at all. You might be working from a customer print that names a specific qualified source: Kennametal, Orwell, Ohio, or a Kennametal source code. In that case, the general insert grade chart is not the controlling document. The approved source is.

I have made this mistake. I saw an equivalent coating type in the chart, assumed it would be fine, and replaced a specified insert with a similar grade from a different source. It machined okay, but that was not the point. The customer had approved that source after testing and repair history. By changing it without approval, I created a quality-record problem and delayed the order.

If a drawing calls out 'Kennametal Orwell Ohio,' treat the grade name, coating, edge prep, and plant source as one complete item. Do not substitute based on the chart alone. In my experience, this is especially important in aerospace, energy, and defense work where traceability matters as much as tool life.

Scenario C: You Are Running a Millennium-Era Machine

I often talk to shops that still run a well-maintained CNC made around 2000. I call these 'Millennium-era' machines. They are not old in the sense of being useless, but they are old in terms of spindle speed, rigidity, and coolant capability.

Here is something vendors do not always tell you: the recommended cutting data on a modern grade chart usually comes from stiff, modern equipment. If you run the chart's preferred speed on an older machine, you may end up with chatter and edge breakage before the coating ever shows its value.

What should you do? Instead of choosing the hardest and most wear-resistant grade at the top of the chart, choose a tougher grade with more impact resistance. You lose a little speed and may even lose a bit of tool life. But you gain process stability, which is worth more than a theoretical productivity number on a chart.

I can only speak to our low-volume and repair work. If you are running a high-production operation with brand new equipment, a harder grade and aggressive speeds may be exactly right. The context is different.

Scenario D: You Are Standardizing Across Multiple Shops or Locations

I have also seen the opposite mistake: a company decides to standardize on one Kennametal insert grade across every plant and every job to simplify inventory. On the surface, that seems responsible. In practice, it can be expensive.

Suppose your main plant machines large steel components on rigid horizontal machining centers, and a smaller shop in Victoria runs mixed batches of thinner parts. If both locations use the same grade from the chart, one of them is probably compromising. The main plant may need a heat-resistant finishing grade. The Victoria shop may need a tougher general-purpose grade because its setups are less rigid.

Standardizing on tool holders and common insert shapes is reasonable. Standardizing on one grade for all applications is not. Use the chart to find the best match for each actual condition, not to force one answer across every machine.

How To Tell Which Scenario You Are In

If you are still unsure, these five questions usually expose the right path:

1. Does the customer drawing name a specific approved source or Kennametal plant? If yes, the answer is traceability, not the chart.
2. Is this a new operation or a repeat job with documented tool life? If it is a repeat job, start with your own records, not the chart.
3. What is the machine condition and age? If you are on a Millennium-era machine or a light-duty setup, choose toughness before maximum speed.
4. How many inserts do you need and how fast do you need them? Availability from your local distributor can matter more than the theoretical best grade for one part.
5. Who carries the risk if the test fails? If you are experimenting with a customer's material, choose a conservative grade and prove it before pushing the limits.

This need for context is not unusual. Someone searching 'why did the first Congress meet' may be asking about the Continental Congress in 1774 or the first federal Congress under the Constitution in 1789. The correct answer depends on context. The same is true with a Kennametal insert grade chart: the right grade depends on what you are actually trying to solve.

A Final Word About Quality and Brand

In my opinion, output quality is brand. When a wrong insert leaves a poor finish, the customer does not ask whether I read the chart. They see a shop that does not control its process. That impression lasts longer than any tooling cost.

The chart is a starting point. The machine, the material, the customer specification, and your own experience decide the final answer. As of January 2025, the current Kennametal grade documentation is still best checked through their official site because printed charts can miss updated grades and edge preparations.

I still keep a printed chart in the tool crib. But above it, I have a note that says: first know the job, then pick the grade. That note has saved us more money than any single insert ever did.