Router Bit Carbide Grading

[Jason Hanko]

Just curious,
What does it mean when a router bit manufacturer lists two different grades of carbide for their bit?
For Example: Rockler lists K10 and K20 carbide for this bit which appears to have one continuous cutting surface (albeit two of them).
Is one of the cutting surfaces made of K10 for finishing and the other side K20 for greater wear resistance?
Or are different parts of the cutting surface made of different grades?
Or are some lots made with K10 and others K20 depending on what deal Rockler got that week?
Confused......

[Ken Garlock]

Hi Jason.

I did a quick 'google' for "K10 carbide" and found a boatload of hits. Basically, the difference between K10 and K20 is shock resistance versus longevity. It is an inverse relationship. The K10 will last longer, but is more susceptible breakage. The K20 gives you more shock resistance, but gives up some longevity.

Do the google exercise, and you will find more than you want.

[Greg Sznajdruk]

Last months FWW had an article on this very subject.

Greg

[Jason Hanko]

Yeah Ive read the FWW article, and have a pretty good idea what the different grades mean. My question was more about what it means if there is a K10 and K20 grade given to the carbide on the same router bit.
How/why does the bit have two grades?

[Rick Fisher]

Are you sure those bits arent between K-10 and K-20. Put up a link.

K-10 Carbide is much more expensive than K-20.

CNC bits are usually between K-0 and K-5. They cost.... a lot more.

You can get K-15, K-8, whatever you order (as a mfg.)

[Cliff Rohrabacher]

Back in the bad old days when carbide was only found in Machine shops the carbide one saw most commonly was a more coarse grade than is now available.
You couldn't get a fine edge on it and if you did it wouldn't stay. The way one cut with carbide was by applying pressure. If you took it to the Diamond wheel to grind it and then to the microscope (We had a 500 to 1 J&L Comparater) you could see the edge was just a long run of chips. The smaller the better but still chips no matter how careful you were at the grinder. Carbide was made from much more coarse grains than it is today.

Now carbide has more properties that range from the coarseness of the grain to it's ability to tolerate shock.

I read the FWW article and wondered at two things. (a) did they not know that man made diamond is harder? and (b) who came up with that bit about pitch and resin pulling the carbide apart? It's not that weak a material. Chips that were going to come off will get caught in any sticky stuff on the teeth but I won't be sold on that myth.

[Tom Walz]

Dear Cliff Rohrabacher

I was privileged helped with the research on the FWW article. I think maybe those two points are better looked at as editorial decisions to keep the article pertinent to the readership than out and out mistakes.

You are correct, of course. Diamond is harder than tungsten carbide. There are a couple materials that are currently laboratory only that may also be harder than tungsten carbide. (I believe one is a rearrangement of the structure of CBN.) However none of those are all that relevant to the FWW reader.

I agree with you about pitch on the saw blade. That my have been my fault because I didn’t make it completely clear to the editor. One of the ways carbide ‘wears’ is through adhesion. As I am sure you are aware, this can be a real problem in metal working. It is not so much a problem as a contributing factor in wood working. The saw tip gets very hot and the saw body gets hot. They cool when out of the cut. A layer of pitch serves as a good insulator and doesn’t allow the blade and the tip to cool as much as it might otherwise.

I think it is a pretty minor contributing factor on the carbide and more important on the saw body.

There are other opinions and some consider it very valid. Personally I seem to consider carbide much tougher than most folks do but we are in that part of the market.

We specialize in high performance carbide which means very tough, long wearing and chemically resistant. See www.carbideprocessors.com under materials for articles on carbide including our shotgun test and our oven cleaner test. These are a lot more demonstrations than actual tests but they help make the concepts more familiar.

Tom

[Tom Walz]

Dear Jason Hanko,

They are working on carbide that is very different on one side than the other. Also grinding carbide changes the structure in a very positive manner. However K10 – K20 generally means that it can be used in both applications but it is horribly vague. There is a good article on this at http://www.ctemag.com/dynamic.articles.php?id=114

There is more on our web site at www.carbideprocessors.com.

In my opinion the most important designation is the name Rockler.

Tom