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What are Kerf Marks?

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  • Written By: Mary McMahon
  • Edited By: Bronwyn Harris
  • Last Modified Date: 23 October 2014
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Kerf marks are marks left behind by a bladed instrument like an axe, saw, or knife. Often, kerf marks form a very distinct pattern, which can be useful from a number of perspectives. In home design, kerf marks are sometimes used to create a feeling of hand-hewn planking, and they may be left intact on antique furniture to emphasize that the furniture was made by hand. In criminology, kerf marks are used to learn more about the weapons used to commit a crime, and sometimes kerf marks are so unique that they are almost like fingerprints, becoming a key aspect of a case.

Any bladed instrument is going to leave some sort of mark as it cuts through material. The type of kerf mark created varies, depending on factors like the material the instrument is made from, the type of blade, the weight behind the blade, and how the blade is used. For someone who is familiar with studying kerf marks, these small marks can tell a fascinating story about a series of events, and they can be used to reconstruct a scene.

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In criminology, for example, kerf marks can be used to narrow down the type of weapon used to commit a crime. Knives, axes, saws, and other weapons all leave unique signatures behind. Hand-held saws and power saws behave differently, while serrations of different widths leave markedly different signatures behind. Someone who hesitated might leave a false start, a partial cut next to the completed cut which can be used to generate even more information about the weapon used.

On television, it seems like criminal investigators are always uncovering kerf marks and miraculously tracking them to specific weapons. In fact, this doesn't happen very often, but sometimes it does, thanks to the efforts of researchers who have devoted their careers to the study of kerf marks. More frequently, forensic examiners generate a list of weapons which could have potentially been used, giving investigators more to work with.

While it helps to have years of experience to study kerfing, sometimes you can find examples around your home and garden which might be interesting. You may also have noticed that different types of saws behave differently when you use them, and if you examine the ends of cut wood after sawing them, you can see the kerf marks you left behind, often along with false starts, if you aren't familiar with using a saw.

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jmc88
Post 5

@cloudel - I really like your method of living with the imperfection to give your flower bed a more natural look.

For times when you do need an even look, does anyone know of ways to minimize the appearance of saw kerf on a piece of wood? I was cutting something with a band saw, and realize after I cut in an inch that I hadn't measured the distance right. Now I have the right size piece of wood I need, but there is an unfinished cut. I don't have any more scrap wood that would be big enough to make another piece.

Could you just use wood filler or something else to fill in the crack? Would that hold?

cardsfan27
Post 4

I have always heard of kerf used when referring to the section of wood that was taken out by a saw blade, but I had no idea the same term was used to refer to weapons used in a crime. I thought that was really interesting.

I have used a bunch of different saws, and like the article mentions, you really can start to tell saw kerfs by the marks they make. You can see the round marks caused by a table saw. Scroll saws always leave a slightly wavy edge.

The saw kerf is what causes pieces of lumber not to be the exact size they are sold as. A 2x4 for example, is actually a little smaller because of the kerf of the saw that cut it.

cloudel
Post 3

I used a saw for the first time to cut boards to form a frame for my flower bed. I had never used one before, and I left evidence of a few false starts. I started to cut the wood, but the angle wasn’t right, so I had to reposition the saw and start again. Anyone who looked closely at the wood could tell that I was inexperienced by the kerf marks.

I think it lent a more natural look to the flower bed. If I had cut the boards evenly and perfectly, then they would have seemed out of place in an outdoor environment.

StarJo
Post 2

I often got in trouble for leaving kerf marks on the kitchen counter. I hated using the cutting board, and my mother could always tell when I didn’t.

The cutting board smells like onions. We really should have a separate one just for onions and garlic, but we don’t. If I want to cut up an apple, I don’t want the onion taste to taint it, so I try to cut it gently on the counter.

I always have to apply more force than I’d hoped I would need, and the knife usually slips on through, causing kerf marks. Since I am the only one with the aversion to the cutting board, she always knows I am the perpetrator.

kylee07drg
Post 1

One of my favorite television programs often shows a forensic scientist finding kerf marks on the bones of a murder victim. For the purpose of the show and to make the plot more believable, the weapon used is often something with a very unique blade. This makes it easier for the FBI to trace it back to the source.

Tremendous force would have to be used to make marks on bone. For one thing, you’ve got skin and muscle to provide resistance to the blade. Also, bone is super tough. You would really have to be stabbing with a lot of anger, both to reach and permeate it.

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