Burning Desire (Not!)

Thanks for the tips...I use a honing stone. That's how I learned back in high school. Have a grinding wheel but scared to use it to sharpen tools. Guess I need more practice.

The coarse seeded gel wheels certainly run cooler and are less prone to clogging than std alox of #60 or #80 - on those I find it easy to blue the steel, so when getting close to a full bevel grind I do just one pass at a time and allow the blade to cool.

I've spent more time in front of a grinding wheel than most; in the late 1970s I became enamored of the wood molding business and ended up grinding molding knives for about ten years. The high carbon high chrome steels used for molding and shaper knives are about as hard as any steel on earth, and most of the grinding I did was freehand; at the same time it was production work and had to be fast and accurate.

Here's what makes the difference: The right abrasive and a soft bond. The harder the steel, the softer the bond you want in your grinding wheel. The bond is named by a letter, and the further on in the alphabet it is the harder the wheel is. Most home-shop grinding wheels are an M or N bond, very hard. What you want is an H, I, or J bond, 46 or at finest 60 grit, and you want a vitrified bond (VB or VBE).

Next thing, you want a "white" aluminum oxide wheel, not a dark carborundum wheel. The white may actually be pink or even brown, but it needs to be aluminum oxide.

Norton's best cool running fast cutting wheels for hard steel are the 32A and 38A Alox (that's the type of abrasive, not the grit. Grinding wheel catalogs explain the code. My favorite all-time Norton wheel was the 38A46 H8VBE.

You can't lean into the work with a soft-bonded wheel or the wheel will wear away too quickly. Just let the wheel do the work and quench frequently.

One more tip: Always grind the profile or shape of the cutting edge with the cutter held at 90* to the wheel, straight on. Then grind the bevel.

"
Norton's best cool running fast cutting wheels for hard steel are the 32A and 38A Alox (that's the type of abrasive, not the grit."

Not anymore. Our 3X grinding wheels by Norton are a consumer version of Norton's Seeded Gel abrasives (SG) They run considerably cooler than any white Alox wheel. It's night and day. And you are correct about the right binder and hardness. The I grade 3X wheels (the usual kind) are soft, and the combination of softness and the SG abrasive make for an amazingly cool grind. I can't imagine why anyone would use anything else these days.

Thanks for the reminder of the significance of the type of bonding and grit type. This was taught to me by my brother in law years ago. The general public's ignorance evolves from the fact that all grinders are sold with conventional wheels and most of our initial training came from a required shop class where they rarely taught the intricacies of wheels.

I'm by no means an expert at the grinder - having only recently made friends with the tool after reading the article on grinding you wrote for FWW - and the above photo is in line with the worst burn damage I've ever accidentally done to a tool. I'm still using a 60grit Norton white wheel, not a 3X. Since learning to use the high speed grinder my woodworking experience has greatly improved because I no longer put off edge maintenance since a five minute trip the grinder to touch up the hollow on the bevel is much less disruptive than half hour with sandpaper and honing jigs fixing up a flat primary bevel and micro bevel. Freehand grinding + freehand honing = more time woodworking :-)

At this point my only real issue with the grinder is how messy it is, lots of grit particles all over my sharpening bench after running it, especially from dressing the wheels. How do you keep the mess under control? If I'm doing a big batch of grinding (fixing up new to me old tools) in good weather I'll drag it outside but that's not always practical.

Cheers,

Josh