sometime back i saw a video on the jenny and davis youtube channel about why he prefers to cut boards on the bandsaw as opposed to the table saw if you've never seen the jenny and davis channel it's a vlog that follows a young couple as they try to build a business their way it's not necessarily my way but it's interesting and they seem like nice people i'll link to it below in this particular video he noted how he sometimes finds it hard to rip boards quickly on the table saw because he gets these results because that's what's happened to me every single time that i've tried i mean is am i really overlooking something simple um i'd love to know a lot of viewers told him in the comments that he needed a more powerful saw or he needed a better saw blade in fact that's what he did in the follow-up video he got a different blade but as he found it didn't help much because the problem wasn't the tool he's using it was the wood itself and that's what i want to talk about in this video because this is something that a lot of woodworkers experience and it can actually ruin your project the problem is called case hardening case hardening can occur when wood has been kiln dried on an overly aggressive schedule basically they crank up the heat and they drop the humidity and they rush the process so they can get loads through the kiln into the market faster this can cause an imbalance in how the board dries the outside dries very quickly and as those fibers lose moisture they shrink but the inner core of the board hasn't dried enough to keep up those fibers remain swollen with moisture so the rapidly shrinking outer shell can't get smaller or constrict enough because it's being held back by the inner core instead a great deal of tension is created on the outside of the board and a great deal of compression on the inside eventually though that inner core begins to dry as well but the outer shell is already set now as the inside of the board tries to shrink it can't pull those outer fibers inward to accommodate its reduction in size so this reverses the stress now the outside surface is under compression as the shrinking inner fibers try to pull it inward while the inside of the board is under tension as the outer fibers resist its shrinkage this happens a lot with pine especially construction number if you ever ripped a two by four and the kerf closed and pinched the back of the blade you've experienced case hardening but it's one thing if your five dollar two by four is case hardened it's another thing if you've bought a pile of expensive hardwood and now it's useless because this flaw can literally ruin your wood case hardened wood doesn't just pinch the saw blade it's not just about bogging down your saw and leaving scorch marks a case hardened board will often warp or bow after you've tried to cut it straight if you're re-sawing it into thinner pieces it might cup immediately after it's cut in some cases you may even cross cut a piece and find cracks inside the board that you didn't even know were there all of this can ruin your day case hardening is a serious defect that sadly isn't that uncommon and understanding how to spot it and how to explain the problem to your hardwood supplier can make the difference between convincing them to give you your money back or having to swallow that big financial loss yourself fortunately there is an easy way to check your boards for case hardening before you start to cut them into your project parts just cut a small piece from the end of the board then cut a curve through the center of the end grain if you don't have a band saw you can do this with a hand saw what i'm doing is removing some of the core of the board so the outer shell can release its stress and do what it's going to do the remaining outer layers should remain straight but if it's case hardened they will bend either inward to close the curve or sometimes outward to widen the curve you might see results immediately but you should give it some time to see the full effect 24 hours of air drying should do it or some say you can speed up the process by microwaving the piece for 20 minute seconds now minutes 20 seconds and then giving it a few minutes to cool just because one board may be case hardened though doesn't mean the entire pile of lumber has been affected you might repeat the test on other boards as well then take any defective lumber along with your test samples back to the dealer and get your money back if he looks at you like you're an idiot don't tell him you learned about this on youtube that's not going to help your cause instead i'll put a link below this video to a document from the u.s forestry service that explains what case hardening is and how this test works and why it's a defect you shouldn't be forced to pay for print that out and take it in with you be nice though case hardening happens at the kiln not always at the dealer putting the blame on the kiln as you talk to the dealer will get you better results than marching in and saying you sold me bad wood of course if your dealer operates his kiln or if this is a persistent problem from where that dealer sources his lumber you might have to shop elsewhere in the future all of us experience case hardened lumber from time to time but few woodworkers understand what is actually happening and what to do about it so i hope this video helps you in the future see you next time mywoodcutters.com is the sort of small business i like to support stefan is a great guy and he can find you knives and cutters for almost any joiner planer shaper or molding machine and his are the best prices if you're planning to upgrade to a helical carbide cutter head please use the link below this video to check with him before you buy somewhere else some small businesses are just worth supporting
