Using a Marking Knife for Dovetails

[Mark Roderick]

I just started using a marking knife rather than a pencil and it's much better in terms of both accuracy and ease of use.

In my first tries, however, I've noticed a tendency of the knife to slice away a tiny sliver of the tail as I'm marking. Any simple recommendation to avoid doing this?

[David Keller NC]

Mark - Whether this is an issue or not sensitively depends on what you're using as a marking knife. I started out using a penknife ground with a bevel on only one side. As you noted, the long sharp blade has a tendency to cut into the tail rather than ride against it. Same issue with some really nice (but in my opinion, incorrectly designed) ebony marking knives from Garrett-Wade. What finally fixed the problem was a marking knife from Blue Spruce toolworks - the tip is ground to a point, and the sides of the knife are short, so it's possible to hold it so that the entire bevel of one side of the knife is completely down on the end-grain of the tail piece.

[Mark Roderick]

Well, you've just answered my question because the knife I just bought is the Blue Spruce knife!

So the answer is to not just use the tip of the knife to mark the pins on the end grain (I cut tails first), but instead to put the entire cutting edge on the end grain, so that you can't slice into the tails.

By the way, how do you hone the Blue Spruce knife? The blade is so thin (as it should be) that I have trouble "feeling" the bevel when I try to hone it freehand.

[Wiley Horne]

Mark,

Here's what I do with the Blue Spruce large and small knife, as well as Dave Anderson's similar knife, and yet another spearpoint from Derek.....I read the black track that the blade bevel is leaving on the water stone. Hold the knife in one hand: on one bevel, the knife is pulled toward me with my thumb on the blade back; for the other bevel, it's pushed away with forefinger on the blade back. The key for me is to read the track the bevel is leaving. Knife is canted so that the blade bevel is at right angles to the direction of travel. I want to see a black swarf track that is the same width as the bevel is long, and the track should make a smudge that shows it is registering. Once I get the visual cue, I can lock my wrist and hold the orientation.

Read the feedback from the swarf track.

Wiley

[Kevin Groenke]

I've tried a few marking knifes (expensive and more expensive) but have decided that I prefer and get better results with an Xacto knife.

The X2000 with the contoured, no roll, rubberized grip is now my marking knife of choice. The blade is honed by replacing with a new, razor sharp one for $.10 in 10 seconds. The sharp point has no problem getting into the tiniest dovetails. There is also a retractable version with an even smaller blade in my apron pocket.


http://img.thefind.com/images/UQATOzHr1TSGaQxbN7IwJBclppXEF5cWFORkphYzZJSUFFjp65 eXl-sVlyQW5KQW6yXn5-oXJ6XoZ-am6ycnlugXl6Tom1uYm5iZxgOZelkF6QwA?m=1&g=2http://www.staples.com/sbd/img/cat/std/s0200181_std.jpg

[Derek Cohen]

I've noticed a tendency of the knife to slice away a tiny sliver of the tail as I'm marking. Any simple recommendation to avoid doing this?

Hi Mark

My impression is that this occurs because the back of the blade is not flat against the sidewall. It cuts because it is canted.

I like to have a little flex in the blade of my marking knives so that that can be pressed firmly against the sidewall.

The ideal marking knife blade has a combination of length (about 1"), slimness (to get into a skinny tail), stiffness (to retain shape), and flex (for side pressure). Then there is the handle to consider - ergonomics, looks, comfort, control (hold it like a pencil, but recognise that a traditional pencil is not comfortable for long) ...

http://i13.photobucket.com/albums/a262/Derek50/Marking%20and%20Measuring/Markingknife-OliveandJarrah3.jpg

Rob Lee wrote a great (tongue in cheek) review of these. I will get it onto my website in the next few days.

Regards from Perth

Derek

[David Keller NC]

"So the answer is to not just use the tip of the knife to mark the pins on the end grain (I cut tails first), but instead to put the entire cutting edge on the end grain, so that you can't slice into the tails.

By the way, how do you hone the Blue Spruce knife? The blade is so thin (as it should be) that I have trouble "feeling" the bevel when I try to hone it freehand."

Mark - That's pretty much what I concluded. Theoretically, the knife should not take a slice of any of the tail if the flat back is parallel with the plane of the side of the tail regardless of the orientation of the tip, as Derek noted. However, I find that my tails are never so uniform and neat that getting the back perfectly parallel with the plane of the tail is possible - there's always a saw kerf or two that stands a bit proud of the rest of the surface of the side of the tail, so I just opted to put the blade bevel all the way down on the wood for the pins. Seems to work fairly well, though I switch the the large BS marking knife when the wood is thicker than 1", as it's hard to hold this orientation and get the blade all the way to the back.

Regarding sharpening - I polished the back of the BS knives in the usual way (holding it flat on a 4000 grit and then an 8000 grit stone), but I sharpened the bevels in the way that I do with carving tools - with the flat side of a slipstone (also a 4000 grit and an 8000 grit waterstone). You do have to hold the tool and the slip carefully to avoid rounding over the bevel, but the advantage is that you can see the bevel and stone quite well.

[Steve Hamlin]

I find thin bladed spearpoints dashed awkward to sharpen. I rely on the visual cue of the oil/surface water bulging up in front of the edge as I raise the angle to tell me when I'm close, then lock up and pull back a 1/8", raise a smidgeon - if no second small fluid bulge at the edge, I'd probably gone too far, so slower and start again.
Then I use tactile feedback and the black smear as previously mentioned to see if I need to adjust. I'm improving, but not there yet with these.
(OTOH a nice thick Chris Vesper joinery knife or router smoother cutter is a breeze - just click into place and your away)
Cheers
Steve

[Dave Jeske]

I happen to need to hone a lot of marking knife blades and I agree with most all of what has been said :). For stock knives I will lightly hone the back of the blade on my yellow shapton stone (whatever grit that is) and then carefully hold the knife bevel at the correct angle with my right hand and use the index finger of my left hand right on the edge of the blade as it touches the stone. I try to have a 3-point contact with my right hand with one of the contact points being the bevel, one being my small fingers off the side of the stone and the other either my thumb on the stone. (yes, I do not have any feeling there anymore) I carefully feel and watch and take a few light strokes. Without changing my grip at all I look at the bevel and see if I need to make any slight adjustments. (a video would be good here!) Usually honing only takes about 4 or 5 strokes. The marking knife does not need to be super sharp but it needs to be smooth. All this is for a stock knife. If you still find that you tend to shave the wood, there is something you may want to try. Using a fine stone, (mine is the wine colored shapton) give the flat side of each bevel a very slight back bevel. Only a couple of degrees and only a few strokes. This naturally happens over time anyway and I find it can actually be beneficial.