- Joined
- Nov 25, 2003
- Messages
- 1,017
I recently picked up a 36" radius platen from Nathan the Machinist. I used it for the first time yesterday and thought I'd give a little review for those of you who may be interested.
I'm still a relatively new knifemaker (10 months) and have flat ground the vast majority of my knives. I hollow ground my first two knives, then used the platen exclusively until recently when I began using my 10" wheel again.
Here is the set-up. 2HP variable KMG with Nathan's radius platen and chiller.
The knife I'm grinding is a prototype drop point/utility made of .135" thick CPM154. The knife was heat/cryo treated by Peters to 60 RC, so this is a post-HT bevel grind.
Grinding with the radius platen took some getting used to. I treated it as if it were a wheel, but the concave "groove" it establishes is very shallow, which makes it challenging to make consistent passes. When flat grinding, I normally pull the handle of the knife toward me as I approach the tip. When using a wheel (and thus, this radius platen), I pull the tang down as I approach the tip, which results in significantly more movement than what is needed when I'm flat grinding. If you want a nice and clean grind line, you have to follow the exact same trajectory with each pass. With a smaller wheel, this is facilitated by the deep concave groove that gets established as you grind. With the radius platen this groove is very hard to feel.
I started off using blue 60-grit zirconia belts (either Klingspor or Pop's "economy" belts) before switching to 3M 60-grit ceramic belts (I like 977's and 984's). I drift belts off the side of the platen/wheel and ride the edge, usually only using the outer 1/3 of the belt. It wasn't long before my hands became more familiar with the radius platen and my lines started looking somewhat better.
This is what I had when I was almost ready to switch to a 120-grit belt. My favorite 120 belt is 3M's 977, but this belt use to give me fits until I started using a diamond file to remove the abrasive on top of the splice. I don't remember who told me that trick, but it's great advice!!
I stay with the 120-grit until I get to my desired edge thickness, then move to a Trizact A100 before finishing with a Trizact A65.
The resulting bevels are very interesting. They look like a flat grind at first glance, but when you look down at the spine towards the tip you see this.
There's an obvious concave shape there! This knife is going to be a Christmas present for a family member who is an avid outdoorsman, so I'm anxious to hear how this knife performs in the field. If any of you have any experience with such grinds, I'd love to hear your feedback and experience. As it is, I'm planning to use Nathan's radius platen often.
This morning I knocked out the top grind with the 2" wheel . . .
. . . and started working on scales. Who here doesn't like desert ironwood and cocobolo burl?!?
I'm still a relatively new knifemaker (10 months) and have flat ground the vast majority of my knives. I hollow ground my first two knives, then used the platen exclusively until recently when I began using my 10" wheel again.
Here is the set-up. 2HP variable KMG with Nathan's radius platen and chiller.
The knife I'm grinding is a prototype drop point/utility made of .135" thick CPM154. The knife was heat/cryo treated by Peters to 60 RC, so this is a post-HT bevel grind.
Grinding with the radius platen took some getting used to. I treated it as if it were a wheel, but the concave "groove" it establishes is very shallow, which makes it challenging to make consistent passes. When flat grinding, I normally pull the handle of the knife toward me as I approach the tip. When using a wheel (and thus, this radius platen), I pull the tang down as I approach the tip, which results in significantly more movement than what is needed when I'm flat grinding. If you want a nice and clean grind line, you have to follow the exact same trajectory with each pass. With a smaller wheel, this is facilitated by the deep concave groove that gets established as you grind. With the radius platen this groove is very hard to feel.
I started off using blue 60-grit zirconia belts (either Klingspor or Pop's "economy" belts) before switching to 3M 60-grit ceramic belts (I like 977's and 984's). I drift belts off the side of the platen/wheel and ride the edge, usually only using the outer 1/3 of the belt. It wasn't long before my hands became more familiar with the radius platen and my lines started looking somewhat better.
This is what I had when I was almost ready to switch to a 120-grit belt. My favorite 120 belt is 3M's 977, but this belt use to give me fits until I started using a diamond file to remove the abrasive on top of the splice. I don't remember who told me that trick, but it's great advice!!
I stay with the 120-grit until I get to my desired edge thickness, then move to a Trizact A100 before finishing with a Trizact A65.
The resulting bevels are very interesting. They look like a flat grind at first glance, but when you look down at the spine towards the tip you see this.
There's an obvious concave shape there! This knife is going to be a Christmas present for a family member who is an avid outdoorsman, so I'm anxious to hear how this knife performs in the field. If any of you have any experience with such grinds, I'd love to hear your feedback and experience. As it is, I'm planning to use Nathan's radius platen often.
This morning I knocked out the top grind with the 2" wheel . . .
. . . and started working on scales. Who here doesn't like desert ironwood and cocobolo burl?!?
