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I have gone deeper into manual woodworking and marking gauges and, in this case, marking knifes are essential in accuracy, especially for joinery.

I do have a problem though, I keep running my marking knife into the square.

Here's how the marking knife looks like (exact product / photo) :

enter image description here

The square looks so:

enter image description here

The ruler part of the square is a bit thin (I suspect this could be part of the cause), around 0.7mm (a bit less than 2/64").

When I trace the line I press the marking knife against the square (the ruler side) and draw. But as I draw I find out the marking knife grinds against the steel of the square or even jumps on it and rides it.

I try to press less but either this repeats or I'm drifting the knife line away from the ruler.

I try to keep the angle between the knife and the ruler as close to zero as possible while the angle between the knife and the wood piece, close to the angle of the cutting edge, a bit raised as to engage the tip of the knife into the wood.

I also tried some combination square which has a thicker ruler (around 2.1 mm, which is approx 5/64") and it helps only a little. I also get small shavings of metal coming from the ruler and feel the edge of the knife blunting away.

What seems to have some minimal success is to lower the marking knife (in respect to the wood) as to not engage the tip but the less acute / obtuse angle between the cutting edge and the length of the knife. This gets me more registering surface between the back of the knife and the ruler but feel awkward and leaves a strange mark (it's decently deep but feels weird to the hand).

I also have some aluminum speed squares but I am afraid to use the marking knife (hardened steel) with them since I fear I will screw them up...

I have the feeling that I'm doing something really and obviously wrong here as I can see a lot of youtubers successfully using one.

What am I doing wrong? What should change?

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  • This is partly a matter of technique and simply practice — I can assure you we've all had difficulty in keeping a knife (of many different kinds) against a steel straightedge or square as we were marking wood. Wood is just a grabby, difficult material sometimes which doesn't make this easier, but you get some of the same thing with card and hardboard which of course are completely uniform and have no grain structure.
    – Graphus
    Jan 16 '20 at 9:40
  • Are you trying to mark your line with a single cut? This can be done but if you press hard first time (as you tend to if you want to make a single pass) it's said to be the main cause of slips, with the potential for injury. I haven't cut myself using a knife and steel rule in decades but I did early on, and I saw a friend cut themselves really badly (ER visit + stitches) which made me even more resolved to never have it happen again!
    – Graphus
    Jan 16 '20 at 9:45
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    Is this "cross-cut" or "rip" marking? I find the latter encourages wandering, and I have to adjust my technique accordingly: lower angle, slower, lighter especially with the grain.
    – jdv
    Jan 17 '20 at 17:59
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The ruler part of the square is a bit thin (I suspect this could be part of the cause), around 0.7mm (a bit less than 2/64").

I doubt this is directly the cause. The main reason being that many users of these types of knives are using thin steel rules and squares and not having issues.

Also, over my lifetime cutting, scoring and marking with various knife types against a steel edge I've had many instances of the knife riding up on to the steel and I 100% attribute it to me, due to:

  • inattention, basically going on autopilot;

  • trying to work too quickly (a big issue in a production environment) by trying to use a single stroke or,

  • actually moving the knife too fast.

Doing something unthinkingly, obvious risk there!

WRT trying to mark in one go, this can be fine particularly where you need only a very light line. But for anything deeper one light starter stroke followed by 1-2 further strokes pressing a little more firmly (safer now that the knife has a groove to follow) is always superior according to many sources going way back, and continuing to advice given today by many woodworking teachers.

Outright speed is always going to make control and accuracy suffer, here as in anything1.

also have some aluminum speed squares but I am afraid to use the marking knife (hardened steel) with them since I fear I will screw them up...

Yeah I can virtually guarantee you'll pare some metal off an aluminium square and risk ruining that edge. DAMHIK!

What am I doing wrong?

Possibly a bunch of subtle things which together cause the problem, at least that's my guess. Without seeing someone do something it's really impossible to give better feedback...... and even if you can watch them do it you might be no more confident of diagnosing the issue! I've seen this many times over the years, even with pros giving feedback (in various contexts, including sports and various craft tasks).

What should change?

I have some suggestions, and don't know if any of them but the last will prove useful.

Start again from scratch and try to pay attention to everything you do, including your stance (where you are relative to the knife and the edge you're marking against), then change any of them one at a time and see if you notice an improvement. You've already tried lowering the knife angle, I feel this could certainly form part of the solution for you.

Try knifing a line with your off hand and see if you get the same issue. If you don't, then try to notice what you're doing differently there so you can adopt it with your dominant hand. I've done the opposite when working towards being able to do certain tasks left-handed, not sure if it might work the other way around though.

Watch some YouTube vids of people using marking knives with this edge profile (shouldn't be hard to find them!) and see if you can identify what they're doing differently to you. But don't be surprised if you can't spot anything with at least some of them — the technique that works could be very subtly different to the one that doesn't, and at normal working speed it could be impossible to see that difference.

Last suggestion is the knife itself. If you find you just can't use it for this then don't feel any pressure to continue to struggle with it2. I no longer use a single-bevel marking knife at all for this very reason, having made two I found I just couldn't get along with them. I've defaulted back to a basic Stanley knife or a folding utility knife (these use the same blades) at the urging of a friend who rightly pointed out that they're easier to use, safer to have lying on the bench (blade retracts or folds away), and, most importantly, there's no difference in terms of the marks made in basic knife marking.


1 Going more slowly the instances went down to almost zero, and like I say in my Comment above I haven't cut myself doing this in decades.

2 You might be reluctant to choose this option because the knife is then going to waste. But not at all, you're sure sure to find other uses for it. If you think of it as a double-bevel skew chisel you should immediately see how you might use it to help clean up corners in dovetailing (a common use for spear-point marking knives). And generally it will make an excellent joint-cleanup tool. You could also push it dead flat against the working surface to do some paring tasks, could make a superior choice for paring dowels flush in some circumstances.

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  • I did try to use a cheap utility knife (exactly this: ebay.co.uk/itm/… ) and I find it much more comfortable than the expensive japanese one. This is the first advice that I put in practice and it definitely helps! Will try the others too! Thanks! Jan 16 '20 at 17:40
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    Oh yeah those! There's a Japanese woodworking channel on YT and I think the guy uses one of those (sometimes, always?) rather surprisingly, but he does a lot of things untraditionally. Anyway, you probably know there's a widespread thought that the reason you 'should' use a single-bevel knife is that the flat side rides against the straightedge so you get the line exactly where the point is, not offset slightly as it would be with a double-bevel knife (by half the blade thickness). Well maybe that's so, but my Stanley blades are ~0.7mm thick...... [contd]
    – Graphus
    Jan 17 '20 at 7:28
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    For a lot of people +/- 0.35mm (1/100") would be perfectly acceptable! But in reality you can adjust technique so that it's not off even by this small amount. The main recommendation is simply to tilt the knife slightly away from the rule/square (the idea being that the bevel on the side of the rule becomes vertical, taking the error to zero) but another is simply to place the knife tip first. Then you run the steel rule or square up to it until it is stopped by the blade, and then cut your mark. This is a technique that e.g. Paul Sellers has shown many times.
    – Graphus
    Jan 17 '20 at 7:33
  • Yes, indeed I've seen Paul (Sellers) do that all the time. I am a huge fan of his, I always watch his youtube videos. What would be the name (or any hints/clues to find it) Japanese YT channel that you mentioned? Jan 17 '20 at 13:32
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    Yeah Mitch does a lot of stuff influenced by Japanese woodworking, it doesn't surprise me that he'd have one :-)
    – Graphus
    Jan 23 '20 at 7:11
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Keep the flat side of the knife against the rule. Your mark will not be as accurate if you are trying to press the beveled edge against the rule.

Reduce the angle of the knife relative to the board. This will give you more area of contact between the knife and the rule as well as allowing the knife to more gradually sever the wood fibers.

I personally prefer the single bevel blades, but then you need to have two of them (one for each side).

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  • Yes, I always used the flat side against the ruler. That's the point of the marking knife as opposed to a typical knife. :-) I would try a single bevel blade too since I need a dual one only for convenience when doing dovetails. You could probably get by with a single bevel coming from the other side... Funny thing, I tried a simple utility knife with the same square and it acted much better... only that it does not have a flat side unless you tilt it against the ruler, which, even then, worked better.. Jan 16 '20 at 14:03
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You don't actually have to put that much pressure against your square as you make your cut. The bevel of the marking knife will keep it moving against the rule. Try making several light cuts focusing on keeping the knife vertical in the cut and not leaning over the ruler. Then go back for another pass to get a well defined line.

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