Resawn QSWO cupping

[tperson]

Last night I was resawing 10” wide 5/4 QSWO on my Jet 18” bandsaw and had a couple of this unexpectedly happen: 1) the kerf pinched so tight it would (almost) stall the bandsaw unless I jammed a couple of screwdrivers in there to pry it open, 2) the (almost) perfectly quartersawn boards would cup terribly once finished (estimated ¼” in a ½” thick, 10” wide piece), and 3) due to the cupping, there was a loud POP as the last 1/4-3/8” of the cut broke from internal stress. The two pieces I cut last night were sequential from the same board so…internal stress? Odd that they cupped oppositely, the looked like this: (). Any suggestions from the group? Board stress? Somehow a bad setup? Sorry no pictures today, I'll try to snag some tonight. 

[Chestnut]

Oak can be very prone to poor drying as it is a difficult species to dry leading to bad internal stresses. Additionally there could have been a moisture gradient from the outside to the inside of the board. If the cuping from the 2 pieces were opposing each other it likely indicates the board wasn't dry or was too dry.

Did you acclimate the board to your shop environment and start the resaw after the shop sat at the same humidity level for a while? Does the humidity level in your shop sit at the same amount for a while? Also keep in mind relative humidity, what most hygrometers read is temperature based so if you aclimate the board at 50% RH and 45 degrees and heat your shop to 72 to work it's going to create some problems.

[phinds]

Generally, a pinched blade means case hardening which in turn usually implies tension wood

[tperson]

Thanks for the comments, both of you. The issue (potentially) seems to be a combination of you two’s explanation…tension caused by improper drying/moisture gradient. Last night’s escapade was better than previous. I resawed the third piece from the original board and was happy with the overall process. I still received the ceremonial POP as it broke the last 3/8-1/2”, but at least the panels were relatively flat. I’ve cut these three pieces sequentially (meaning the first piece came from the end, the second from the middle, and the third from the other end) and the result has gotten better each time. Less cupping, less popping, better overall. I’ve got one more full length board to cut into 3 pieces and resaw, it’ll be interesting to see how they react.

Below is a picture of last nights resawing, I can live with that. 

[Askland09]

On 2/2/2023 at 10:43 AM, tperson said:

I can live with that.

This quote right here is what helps me get projects done . As long as I can live with it, most people won't even notice. lol. 

[Coop]

Hopefully it won’t get worse as it acclimates. 

[B1rdhunter]

I have been hoping for some magic answer to this question myself but the only one I've found is leave plenty of room for milling after resawing and try to ignore the waste. Back in 2018 I purchased about 2500 bd. ft. of 8/4 from a fairly well respected mill near me but it's a total crap shoot as to which boards will be crazy. The 4/4 has been more reliable but still not perfect. Currently been resawing 8/4 to make 1/4 inch thick panels so I saw, glue and clamp fairly fast to stay ahead of the cupping.

[tperson]

On 2/2/2023 at 9:36 PM, Coop said:

Hopefully it won’t get worse as it acclimates. 

After each evening's activities (planing, running through the drum sander, dyeing, etc.), I've been clamping them flat...and they've been staying relatively flat. If I can get them captured in the headboard this weekend, I should be good-to-go. I hit them with some shellac this morning after dyeing them last night, today will be the longest they've been unclamped.