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My master's thesis is based on tactile detection of surface defects in wood surfaces. I am using standardized 20cm disks made from different wood species as samples for my system.

The control samples are trivial to make by just sanding a defect-free piece of wood properly. The defect samples are where I'm facing issues:

Given that tools are (hopefully) designed to minimize defects as much as possible, it's not exactly easy to produce defects in a controlled and intentional way. Some types are easy (Scratches, dents caused by impacts, over-agressive sanding, etc.), but others like torn/fuzzy/raised grain, chip marks, knife burn, saw marks, aren't.

How can I intentionally produce surface defects (without neglecting safety)?

Intentionally damaging (inexpensive) cutting tools like saw blades is an option.

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    Do a YouTube search for "how to distress wood" Here is one, youtube.com/watch?v=vmPK3VLO_Ks There are both mechanical and finish techniques so weed through to find the mechanical. Bonus, It is fun.
    – Alaska Man
    Sep 23 '20 at 17:59
  • FWIW I don't believe most people will be able to detect (much less differentiate) minor surface defects. Even surprisingly coarse sanding scratches may not be felt, despite how grossly obvious they are to the eye. You have to get down to ridiculously coarse grits like 36 before scratches might be easily detectable by anyone, but even then they're hard to differentiate from the natural features in an open-pored (AKA coarse-grained) wood like the oaks, or for that matter from raised grain caused by post-smoothing wetting of the wood.
    – Graphus
    Sep 24 '20 at 7:24
  • The usual term in English for the tearing of fibres from the surface during planing is tearout. This refers to the occurrence no matter the cause, covering manual planing with a hand plane and machine planing of all types — with a planer/thicknesser or jointer or hand-held power planer. As for the sawing, not sure if you're referring to power sawing or hand sawing, in which case burning would cover the first. In hand sawing there may be burnishing in localised areas, depending on the cut being made and the 'set' of the saw (wider set tending to eliminate it since the saw plate will rub less)
    – Graphus
    Sep 24 '20 at 7:32
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    @Graphus don't rain on the man's parade! He's doing research, some times research proves your hypothesis wrong and that's just as valuable as proving it right - after all, Edison found about 10000 ways a light bulb would not work before he found one that did. Plus, many people can differentiate the bumps that make up letters in Braille - while to me, it's a barely noticeable bump on the paper. Some are more sensitive than others.
    – FreeMan
    Sep 24 '20 at 10:53
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    Just drop the disks off at my shop and tell me: They're important, keep them safe, and do not inflict any surface defects or other damage to them. Return in a week and you should have all the defects you need and then some. Seriously though, @FreeMan's comment is spot on for the scientific method and his answer sounds spot on to me (+1). Start with what he gave you and then pretend you're a new, serious, and careful woodworker and just "work on them." You will be surprised at how easy you can meet most of your requirements.
    – Jim
    Sep 25 '20 at 10:59
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Raised grain is easy - get the wood wet.

Torn can be pretty easy, too - plane or chisel it in the wrong direction or with a dull tool.

I'm not sure what "chip marks" are, exactly, but if you plane into the end-grain (start the plane with the blade off the wood, then dig into it) of the wood, you're likely to tear out a chunk, which may be what you're after.

Saw marks can be fairly easy - assuming you're slicing your "disks" off of a long rod, cut part of the way through, then move the piece slightly while continuing the cut. This is potentially dangerous as you can cause the blade to bind which could grab your wood and throw it. Be extremely careful doing this.

I'm not exactly sure what "knife burn" is, either, but if you use a dull saw or router bit you're likely to burn the wood. I'm not sure that you'd be able to feel the difference (though you can see it), I guess that's part of the research, eh?

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  • I'm not sure if there's a specific name for both, but I'm referring to small chunks being ripped out during planing and the burn marks that occur if the saw rubs against the wood instead of cutting, respectively.
    – JS Lavertu
    Sep 23 '20 at 17:17
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    When I was younger I knew a lot of folks in the TV business in Toronto. They had carpenters whose job it was to make period-looking furniture that was slapped together as cheaply as possible and then thrown around the shop, hit with tools, used for messy lunches, etc. to age and distress it, before and after finishing. It helped to use the knottiest, wormiest lumber as well.
    – jdv
    Sep 24 '20 at 13:21

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