Phil Thien
02-18-2012, 6:42 PM
I know jointer/planer knife sharpening methods/jigs have been done to death. And there is probably nothing new to this technique.
But I'm going to share anyhow...
I have an Inca 410 jointer/thicknesser. It uses 8-5/8" knifes that are 2.5mm (I think) thick. They're difficult to come by.
I found that 3mm thick knives would fit, and found that Amana offered 3mm knife stock in 36" long pieces.
I was going to try cutting it myself using a wet tile saw, but found a shop just a couple miles from my house that makes/sharpens BIG knives for industry. They offered to cut them for beer money. When I arrived, the gent that helped me was honing some knives that must have been about 12-feet long. There is a large paperboard industry in this area and this outfit services the knives for those manufacturers.
I wish I had taken pictures. Imagine 12-foot long jointer knives (like an inch thick and a few inches high). Kind of amazing. When I was explaining that I needed the lengths the same so the weights would match (for balance) the guy helping me kind of rolled his eyes. When I went to pick them up the next day, he showed me that both the lengths and weights were all perfectly matched, and I handed him money for beer. I can't remember how much.
That was a complete tangent. Sorry.
Anyway, due to the rarity of these knives, I was happy to fall into a couple of real Inca 410 knives. They were poorly sharpened at some point. It sort of looked like they had been free-handed on a grinder by the previous owner. They were out of straight by almost 1/16" (in a wavy sort of way).
I have a Woodcraft wet sharpener I've used (http://www.cgallery.com/jpthien/ws.htm), but these knives were so wonky I needed a method to grind 'em straight. And this is what I came up with.
I basically cut a board with two 38-degree slots to hold the knives bevel OUT. The knives are a friction fit. I glued a small sliver of wood into the ends of the slots to keep the knives from sliding sideways.
I clamped a straight board to my drill press table to act as a fence, chucked a 1" diameter by 1" long diamond drum in the chuck, and started grinding away. The edge of the board that holds the knives registers against the fence board I clamped to the the drill press table, and results in a nice straight grind (with one caveat, and I'll go into that later). I ocassionally adjusted the fence backwards by tapping it on one side or the other with a little wooden mallet.
ANYWAY, once that is done I put the knives into another board with two 45-degree bevel cuts, this time with knife bevels UP. I hone the knives so the scratch patterns are headed in the right direction. This gives me a sort of micro-bevel (it isn't that micro, but...).
The result is nice, straight knives that are extremely sharp. And the process goes quite fast. That diamond drum makes quick work of the process.
While the knives don't tend to get very warm, the diamond drum can. I noticed this after a lot of grinding. I can keep my hand on the drum, but I think caution is in order. For touching-up the knives, I don't think this will be a concern. I was removing a ton of material.
Anyway, that is one more method for sharpening knives.
But I'm going to share anyhow...
I have an Inca 410 jointer/thicknesser. It uses 8-5/8" knifes that are 2.5mm (I think) thick. They're difficult to come by.
I found that 3mm thick knives would fit, and found that Amana offered 3mm knife stock in 36" long pieces.
I was going to try cutting it myself using a wet tile saw, but found a shop just a couple miles from my house that makes/sharpens BIG knives for industry. They offered to cut them for beer money. When I arrived, the gent that helped me was honing some knives that must have been about 12-feet long. There is a large paperboard industry in this area and this outfit services the knives for those manufacturers.
I wish I had taken pictures. Imagine 12-foot long jointer knives (like an inch thick and a few inches high). Kind of amazing. When I was explaining that I needed the lengths the same so the weights would match (for balance) the guy helping me kind of rolled his eyes. When I went to pick them up the next day, he showed me that both the lengths and weights were all perfectly matched, and I handed him money for beer. I can't remember how much.
That was a complete tangent. Sorry.
Anyway, due to the rarity of these knives, I was happy to fall into a couple of real Inca 410 knives. They were poorly sharpened at some point. It sort of looked like they had been free-handed on a grinder by the previous owner. They were out of straight by almost 1/16" (in a wavy sort of way).
I have a Woodcraft wet sharpener I've used (http://www.cgallery.com/jpthien/ws.htm), but these knives were so wonky I needed a method to grind 'em straight. And this is what I came up with.
I basically cut a board with two 38-degree slots to hold the knives bevel OUT. The knives are a friction fit. I glued a small sliver of wood into the ends of the slots to keep the knives from sliding sideways.
I clamped a straight board to my drill press table to act as a fence, chucked a 1" diameter by 1" long diamond drum in the chuck, and started grinding away. The edge of the board that holds the knives registers against the fence board I clamped to the the drill press table, and results in a nice straight grind (with one caveat, and I'll go into that later). I ocassionally adjusted the fence backwards by tapping it on one side or the other with a little wooden mallet.
ANYWAY, once that is done I put the knives into another board with two 45-degree bevel cuts, this time with knife bevels UP. I hone the knives so the scratch patterns are headed in the right direction. This gives me a sort of micro-bevel (it isn't that micro, but...).
The result is nice, straight knives that are extremely sharp. And the process goes quite fast. That diamond drum makes quick work of the process.
While the knives don't tend to get very warm, the diamond drum can. I noticed this after a lot of grinding. I can keep my hand on the drum, but I think caution is in order. For touching-up the knives, I don't think this will be a concern. I was removing a ton of material.
Anyway, that is one more method for sharpening knives.