Help with sharpening a drawknife

[Claus]

I got a good deal on this from a local guy on Craigslist but it needs some work. My sharpening experience has evolved as far as “get a good edge/bevel and then frequently touch that up with high grit and honing before the tool gets too dull”. Grinding to straighten a wavy edge before sharpening is beyond my experience level. I would appreciate any and all suggestions and your preferred method.


Thanks,
Claus

 

[bob vaughan]

Two methods I've used with the bench grinder. I like the latter better. It uses a platform I screwed to the tool rest and a wood holding jig.

 

[Claus]

Wow. That’s an amazing amount of detail and something I think I can set up. Thank you. A few of questions-
— what’s a good bevel angle? Do you suggest a primary and secondary like that of a hand plane blade?
— In my mind I feel like the blade will follow the wheel in its current shape, as in a curved blade will grind an edge along the same curve. Is that true? Will this remove that “low spot” in the middle? Does that make sense?

 

[Mike Davis]

I use a 2x72” belt grinder like a lot of knife makers use. I grind by hand and eye. After many years of practice it seems easier for me that way. I’d be happy to clean that edge up for you and show you how to keep it sharp.

 

[bob vaughan]

I just tilt the tool rest until the wheel touches in the middle of the existing grind profile.
As to a numerical designation to the angle, I use the method I learned from a friend that does aircraft maintenance: TLAR (That Looks About Right).
Sharp is a whole lot more important than the angle with a drawknife.
Once ground to shape, I'll sharpen like I do other edged tools. Never a secondary bevel. With the sharpening stone riding on the two edges, that isn't necessary.
Crappy drawing below.

 

[SabertoothBunny]

I just tilt the tool rest until the wheel touches in the middle of the existing grind profile.
As to a numerical designation to the angle, I use the method I learned from a friend that does aircraft maintenance: TLAR (That Looks About Right).
Sharp is a whole lot more important than the angle with a drawknife.
Once ground to shape, I'll sharpen like I do other edged tools. Never a secondary bevel. With the sharpening stone riding on the two edges, that isn't necessary.
Crappy drawing below.

View attachment 225184

So do you leave one side of the draw knife flat and only shape the one side of the edge fro drawing? I assume that is to allow the flat side to "ride" on the wood to reduce cutting into the wood when removing bark?

 

[bob vaughan]

I've always left one side flat and bevel the other side. That's the way I've found most drawknives that were in good condition so I just imitated what I found. I don't see why grinding both sides wouldn't work, its just that I've never tried it. Holding the handles would be of a little different angle but I don't see why that wouldn't work. A drawknife is not a precision cutting instrument anyway.

 

[Graywolf]

I’ve never seen a knife edge ground on a draw knife. To me that would take away from your ability to control the cut. Much the way Bob has illustrated this gives you the ability to use the tool on the flat or on the bevel. That gives you much more control of the cutting and slicing action of the tool.

 

[old and in the way]

I'm no expert on drawknives, but yes, I think that you would leave one side flat so that you have a reference point for how much material you might try to remove with one pass. Sort of like a wide chisel, better to shave than to gouge.

I will also agree with both the hand and eye grinding method, as well as the TLAR methodology, which applies to almost everything wherby experience teaches that a range of different approaches will produce similar results.

FWIW
Tone

 

[Mike Davis]

I use a draw knife quite a lot for both large debarking work and delicate precision shaping.
I always have one flat side. Every draw knife I have ever seen has one flat side.
Where I differ is the beveled side. I use a convex bevel similar to a carving ax.
The convex bevel allows you to ease out of a cut as slowly or abruptly as needed.
And it should be as sharp as a knife, scalpel even. Highly polished is also desirable.

 

[bob vaughan]

I've spent way more time sharpening drawknives than I have using them. For years our Boy Scout troop had three shaving horses that we would take to camp plus the camp had many knives for their outdoors programs. I ended up being the go-to guy for drawknife sharpening for them all for many years. I had to come up with a way to get the job done as quickly and easily as possible. What I posted above is what I came up with. I found it easier and faster than using my 2x48 belt grinder except in cases where the drawknife was an abused wreck that had been donated to the cause.