Cleaned Saw Blade Too Well?

[jackellis]

I've been using Simple Green to clean my saw blades. Until today, I used an old toothbrush to scrub the gunk of the tooth face with no problems.

Tonight I cleaned a Freud TK306 using Simple Green and a brass brush, thinking the job would go faster and take less effort.

I'm not sure whether it's the cleaner or the brush but I noticed that the faces of a number of blade teeth have what appears to be damage to a coating on the surface of the tooth face. It's as if the tooth face had a thin powder coating or some other protective surface that appears to have been damaged by cleaning.

This photo is about the best I could to to illustrate the problem:



Any thoughts on what happened? I doubt the blade is trashed but I'd like to get to the bottom of this before I clean any more.

[LCHIEN]

there is no coating I know of used on carbide.
It would have to be harder than the carbide to be of any use.
What you could be looking at is the difference in color/texture between the carbide and the brazing used to attach it to the saw blade body.

[scmhogg]

Simple Green has recommended against soaking carbide in their regular product. A recent magazine article said to use Simple Green for airplanes instead.

This is the quote from the SG site--

BLADES, CARBIDE & SAW BLADES
Simple Green has been successfully used by many woodworkers over many years as a good "spray - wipe - rinse" cleaner for saw blades. When pitch is fairly fresh (typically within a 12-hr period since deposit) it is fairly easily removed with Simple Green. Older, dried-out pitch is much more difficult to remove. We do not recommend long-term soaking of Carbide blades in Simple Green. Long-term exposure like this can possibly cause cobalt leaching that will, in turn, affect the integrity or carbide. Shorter term "spray/wipe/rinse" applications do not create that kind of problem.

[Slik Geek]

The cobalt leaching that Simple Green cautions about can be better understood if you know how the carbide tips on your saw blade are manufactured:

Tungsten carbide powder is sintered at high temperatures with cobalt power. The cobalt works as a binder for the carbide. The two materials don't react, the cobalt simply acts like a glue with carbide particles suspended throughout. By adjusting the ratio of cobalt to carbide, as well as the size of the carbide particles, the manufacturer can control the characteristics of the final product - hence the differing grades of carbide (and varying brittleness).

Other compounds are also used as binders for carbide, but cobalt is the most common, I believe.

Damage due to cleaning occurs when the binding material is corroded. (Tungsten carbide is tough stuff so it usually is unaffected). Hence, one must consider if the cleaner is compatible with the binder. If the binder is corroded, the surface of the tips become weakened because the carbide particles are left with minimal structural support.

One sign of severe corrosion is a dull appearance in the carbide. (Do you have another blade that you can compare to?) Another sign is when, after use, the carbide chips away, resulting in a pitted surface.

[Knottscott]

Jack - A soft brass brush shouldn't damage carbide....I use them often to clean my blades.

[Pappy]

Cheap brass brushes, like the ones from HF, can leave a deposit on the blades. Maybe that is all you are seeing.

[jackellis]

I don't soak the blades because the pitch comes off easily enough without it. Others had mentioned the potential for blade damage from soaking when I first started reading up on this years ago. I don't use oven cleaner for the same reason. Simple Green stays on for no longer than about 10 minutes, which is just enough time to scrub.

The brass brushes are from HF. Thanks for the tip, Pappy.

The faces of the teeth on this blade are dulled in places compared with the sides, and that's what shows up in the (poor) photo. That's what has me so mystified. I'm going to put the blade back in and do some cutting today, then pull the blade and reinspect.

I've cleaned the stock blade and some Irwin blades this way. Never seen anything like it.

[JimD]

I use CMT's blade cleaner and can remove pitch even after I've burnt it a bit with just a paper towel as long as I do not let it build up too much. Even then, I repeat squirt and wipe is all that is necessary - no scrubbing. I am also prettys sure it doesn't hurt the blade.

Jim

[Andrew Benedetto]

Freud says to use kerosene. I use diesel fuel. Any hi alkaline solvent is harmful. Simple green is not a neutral pH and not good on the metal structure.
I also have used hand cleaner;"GOOP ORANGE" , no issues there.
I have read where some use a potato to rub the blade and tips with a cleaner too, I use an old CreditCard but a soak is all that is usu. needed in the solvent.