Radius platen - hybrid rotary platen?

[Brock Cutlery]

Forgive the quote out of place, but this question just didn't seem to belong in the for sale arena.

Radius platens simulate large wheels. They're called a "radius platen" because they're machined with a radius. The size number references the size wheel they simulate. So a 36" radius platen actualy has an 18" radius. It simulates a 36" diameter wheel.

In using the radius platens I have found the effect is subtle, but noticeable. It isn't a flat grind, but it isn't really a hollow grind. I believe this is a historically accurate grind for blades ground in yesteryear on really big stones. I see this being a cool grind for blades made in an older style, and blades like kitchen knives where you would want a full height grind on a tall thin blade.

The A2 is quality steel from Latrobe, heat treated at Peter's Heat Treat with cryo and is harder than a woodpecker's lips. But it can still wear out quickly if exposed to certain grinding conditions that cause grinding grit to accumulate on the inside of your belt and cut the platen. Some belts have dry lubricants, coolant and other "aids" that work great on a contact wheel but can cause black gunk buildup on the inside of the belt that can then cut the platen, particularly when they get hot or damp. If you're getting black buildup on your platen beware of cutting grooves.

Unlike a flat platen that you can re flatten, a worn out radius platen is toast. You can extend the life of your platen by not using it to rough or profile. If you establish your grind on a regular flat platen or wheel and if you'll avoid cutting it with grinding grit your radius platen will develop a mirror finish and can grind hundreds of knives over its life before developing troublesome wear.
You will probably want a platen chiller if you're using a radius platen, particularly the 36" and 48".

Nathan, or anyone really,
I wanted to ask if you've ever considered running a rubber belt under the grit belt, but over the radius platen. Something like Beaumont's rotary platen attachment:



I'm not sure how it would affect cooling or platen wear, but as far as grinding, it seems it would act more like a true wheel. Thoughts?

 

[mike-E]

im pretty sure it would just eat the rubber belt up.

 

[Brock Cutlery]

im pretty sure it would just eat the rubber belt up.

You could be right. I hadn't considered that. I think the platen could be much shorter.
On a radius platen it isn't like you would be using 8 inches of it. But I'm not sure that would help the heat or wear too much.

 

[StuNY]

Not sure if it is worth the trouble? Have you tried using a radius platen as is? I made one a few weeks ago at 36" diam and it works very well. I have been making Urasaki grinds on the backs of my traditional Japanese knives and it is easy and accurate to use. Haven't found it heating up much for my limited use and the belt rides the arc perfectly even under a bit of pressure.
Stuart

 

[Brock Cutlery]

Not sure if it is worth the trouble? Have you tried using a radius platen as is? I made one a few weeks ago at 36" diam and it works very well. I have been making Urasaki grinds on the backs of my traditional Japanese knives and it is easy and accurate to use. Haven't found it heating up much for my limited use and the belt rides the arc perfectly even under a bit of pressure.
Stuart

I'm glad you posted that info. I keep thinking about getting one of these but I have had no idea what I might expect from it. I have a 14 inch wheel, but long for a bigger arc.

 

[javand]

I'm glad you posted that info. I keep thinking about getting one of these but I have had no idea what I might expect from it. I have a 14 inch wheel, but long for a bigger arc.

You can glue a piece of rubber to this or a flat platen, and use a piece of the 3m micron polishing belts (mylar) turned grit side to the rubber, glued on top of the rubber, and a belt will ride this reasonably well, at low/medium speeds with low pressure.


The polishing belt piece will wear out and have to be replaced regularly, and if you run too fast with too much pressure you'll gouge the rubber and/or send it flying, and potentially break belts, however, with care, this can be effective.


Obviously not for rough grinding. I wouldn't consider doing this before 120 grit.

 

[Brock Cutlery]

You can glue a piece of rubber to this or a flat platen, and use a piece of the 3m micron polishing belts (mylar) turned grit side to the rubber, glued on top of the rubber, and a belt will ride this reasonably well, at low/medium speeds with low pressure.


The polishing belt piece will wear out and have to be replaced regularly, and if you run too fast with too much pressure you'll gouge the rubber and/or send it flying, and potentially break belts, however, with care, this can be effective.


Obviously not for rough grinding. I wouldn't consider doing this before 120 grit.

Another cool trick. Thanks Javand.

 

[elementfe]

Just a little plug for Nathan's platens- I use mine on hunting knives, instead of a plain flat grind, and it makes a very nice looking bevel, catches the light just so....looks like it's going to last forever, even without a cooler.