Marking Knife Technique - Help!

[Jeff Cord]

I just purchased a marking knife (from Lee Valley) and am having problems using it.
I'm just messing around trying some dovetails (I'm learning to do them as well).
I do the tails first, no problem.
When I try to scribe the lines for the pins with the knife I wind up carving some of the tails off with the edge of the knife.
Is there something I'm missing?
thanks,
Jeff

[Don C Peterson]

It's practice that's needed... I had the same problem, I was either slicing into the tails or wandering off of the tails. With practice you get to know the knife and at what angle you need to hold it in relation to the tails.

I'm gonna take a guess that you might be pressing too hard, you don't need to cut the pins with the marking knife... Pressing too hard will have you off following the grain instead of the pattern.

HTH

[Carl Maeda-San Diego]

Exactly what I was going to say... don't press so hard and it should be ok.
If the knife is sharp, light pressure is all you need.
I had the same problem too.

[Rick Erickson]

Jeff, that is a common problem with most marking knives. They aren't really designed to trace dovetails. Try filing a very slight chamfer on leading edge. That will lessen the likelihood that it grabs. I know that Rob Cosman is working on a marking knife specifically designed for dovetail work. I got to see a prototype a few days ago. It is designed to solve this problem.

[george wilson]

When you saw the first of the mating pair of dovetails,take a piece of sawblade steel the same thickness as your saw,or use the saw itself. Lay the one set of sawn dovetails uopn the other,so they don't shift,and scribe through the dovetail cuts with the scraper,or draw the saw backwards to mark the other dovetail. Then,saw the next dovetail pair on the exact outside of the scribe marks you made. Hope this makes sense. This is not the way I do it,because I always do everything the hard way.Roy Underhill did it this way on one of his shows. I won't even get into how I do it. Everyone is different. I rely upon skill long practiced,but the scribed lines would help someone newer.

[Stephen Shepherd]

Jeff,

The problem is probably from holding the knife at too low an angle, making it more of a knife than to just strike the line.

Try using the marking knife in a more upright orientation so just the point of the knife marks the pin without cutting into the tail. It also may be too sharp.

Stephen

[Sean Hughto]

Is this what you got from LV?:
http://www.leevalley.com/wood/page.aspx?c=2&p=60044&cat=1,42936

If so, you are correct that it is your technique that is the problem. The flat back should be the part contacting the tail "cheek." It should be be at like 80 degrees not 45 as you mark. If you are at a low angle relative to the plane fo the endgrain you are marking the blade tip will have a tendency to slide under the edge of the tail cheek because the tip is looking for something to register on. Let as much of the back of the blade register as possible so the tip can't get under the edge being marked.

[Pam Niedermayer]

Here's a tip from Jeff Gorman: hold the marking knife bevel flat against the straight edge while marking. This is nonobvious but it really works. However, it won't work for dovetails since you don't have the space.

Pam

[Jeff Cord]

Stephen and Sean, you seem to be giving contradictory advice.
Holding the knife more upright versus holding the knife at a lower angle (I believe that's what you're saying).
I try to keep the back of the knife flat against the "cheek" of the dovetail but that doesn't seem to be helping.
I'll keep practicing with different angles to see what helps.
thanks,
Jeff

[Derek Cohen]

Stephen is correct that the dovetail marking knife must be held fairly vertical.

One of the characteristics I like in a dovetail marking knife is a thin blade (thin enough to fit inside a .020" kerf) and has a little flex that will hold it flat against the fence.

I suspect that the ones made by Dave Anderson (Chester Toolworks) and Dave Jeske (Blue Spruce) will work like that. The ones I make are stiffish HSS with a little flex.

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

One of the crazier dovetail knives I made, some years ago, was one that was fashioned out of a steel garden trowel. The idea came from Tage Frid. The idea was to hammer a flat piece of steel (he used a bandsaw blade) into the kerf ..

http://i13.photobucket.com/albums/a262/Derek50/Chisels/Dovetailkerfer.jpg

http://i13.photobucket.com/albums/a262/Derek50/Tools%20that%20I%20have%20made/Chiselmarkingknifedemo1a.jpg

:)

Regards from Perth

Derek

[Dave Jeske]

Derek,
We should trade some marking knives some day. I like the lacewood handles on yours. I make my smaller knives with two thickness of blades. The standard is 1/32" or .032". I also make an "ultra-thin" version for doing single entry dovetails that has a blade thickness of .020. This seems to work well with even my thinnest blade Western style saw. The blade is a bit flexible so you need to be extra careful to make sure you are marking accurately.
Dave

[Derek Cohen]

Hi Dave

Thank you for the compliment. Sounds a great trade to me! :)

I am shortly off to Cape Town for 2 weeks (anyone know of anything going on there?), and will contact you on my return.

Regards from Perth

Derek