# Need some guidance for resawing



## MikeMD (Apr 13, 2011)

I am attempting to learn how to resaw and my first few efforts have been a mixed bag.

I have had horrible cupping problems while trying to saw 1/2" thick material out of 4/4 and 6/4 material. I measured the moisture content before sawing and it was below 10%. Were my measurements likely off or were there other factors contributing?

When trying to take 4/4 material to 1/2 or less I was hoping to just resaw but getting this cupping is making it impractical. I know I am doing something wrong, I just don't know what.


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## gfadvm (Jan 13, 2011)

By cupping, I assume you mean the blade is bowing inside the board. A dull blade, feeding the stock too fast, and/or insufficient blade tension are the most common causes of this. I assume you are not using a narrow blade or a high tooth count blade to try to resaw? A resaw blade should have only 2 to 3 teeth per inch and I would use the widest blade your saw will handle. Hope this helps as resawing can be very rewarding.


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## Danpaddles (Jan 26, 2012)

I have had a journey of continual improvement while re sawing. I have made just about every mistake possible I think! I still do not get great results, I always leave a little extra for the planer to clean up. There are many variables, I still often miss one small detail, and end up with a goofy board.

But every once in a while the stars align, and I have a nice board to show for it. When that happens, I am still frustrated, because I probably left extra thickness in anticipation of goofs. So I still end up running the planer far too long.

I'll keep trying if you will! In the meantime, I keep reading whatever advice I can see, even though I have heard it all at one time or another.


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## JAAune (Jan 22, 2012)

Sharp blades are the first step to successful resawing. I use 1/2" 3tpi skip tooth blades for general purpose cutting and resawing with success. Don't use more than 3tpi. I've gotten good cuts with a 4tpi blade before but the feed rate was unacceptably slow.


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## MikeMD (Apr 13, 2011)

My problem is not the initial cutting. After letting the cut boards rest for a bit they end up with a lot of cupping. Too much to joint and plane out. So, I have several very cupped boards now. I'm trying to figure out how to minimize/predict this.

Outside of moisture content, I'm not sure what I should be looking for or what I can do to minimize this.


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## gfadvm (Jan 13, 2011)

Sorry I misunderstood MikeMD. I would suspect inadequately dried lumber OR it is absorbing moisture on the convex side after it's resawn. Flatsawed lumber has a greater tendency to cup than quartersawn.


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## JAAune (Jan 22, 2012)

Hmm okay. I've seen some cupping like that but it's usually not too bad. As Gfadvm says, improperly dried wood can cause problems like this. Make sure that the wood has actually reached equilibrium moisture content in your shop before resawing it. Otherwise, the thinner boards dry faster and will cup depending upon how they are sawn from the log.

Even properly dried wood will likely have some internal stresses if the growth rings aren't evenly distributed in the board. That's why quartersawn is the most stable.




























Out of the above three example boards, the first and the last would be less likely to have internal stresses than the middle one. As wood dries, boards tend to move in such a way that the growth rings tend to flatten out. I'd expect to see some noticable cupping if I were to slice through the middle of the board in picture number two.


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## HerbC (Jul 28, 2010)

Mike,

Cupping of wider boards after resawing is quite common. It is due to moisture imbalances between the original outside side of the resawn board and the newly exposed side. Letting the board acclimatize (sp?) longer before resawing may help. The other thing that can help is to stack the resawn boards up in your shop with stickers to provide for airflow between the boards. Put weight on top of the stack and let it rest and continue the drying process. Make sure the stacking surface is flat and that the stickers are uniform thickness and are straight. Place the stickers about twelve inches or less apart horizontally and in line with each other vertically.

Good Luck!

Be Careful!

Herb


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## fussy (Jan 18, 2010)

What kind of wood are you trying to resaw? If it is properly dried hardwood, it shouldn't be doing this. Therefore it isn't properly dried or hasn't acclimated to your shop. It should sit in your shop for at least a week or two for 4/4 material. Longer is better. If it's lumber yard softwood, it's too wet from the store, was probably cut from too small a tree with stress or pith. Use better and better dried stock. As Danpaddles said, it's a journey.

Steve


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## Kelby (Oct 19, 2011)

Some cupping is inevitable. You will always need to face joint and plane after resawing. However, keep in mind that the moisture content of the wood is not the only critical variable-you also need to pay careful attention to the humidity level in your shop. If your shop humidity is lower than 40% or higher than 60%, then you will see significant cupping even if your wood was properly dried. Remember that when you resaw, the fresh face tries to reach equilibrium with the air in your shop. It's not the wood moisture that kills you, it's the magnitude of the delta between wood moisture and shop humidity.

If the wood is under 10% and the shop is between 45-55% humidity, that's ideal, but I still would not expect to get 2 pieces of 1/2" out of 4/4 material unless it was on the thick side to start with and I got very lucky. There's just not enough meat there to account for blade kerf and a small amount of jointing/planing after resawing. I would generally use 6/4 to get 1/2" slices.


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## renners (Apr 9, 2010)

What width are these 1/2" boards when you have finished? Are you able to save them by ripping them down and turning the growth rings to alternate and gluing?
I have had bad cupping problems on 5" wide 4/4 walnut on the same day as having perfect resawing on 5" wide 8/4 walnut, so I'd most likely say it's the wood.


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## MikeMD (Apr 13, 2011)

It's the wood. Thank you all for the insight. I need to be more careful acclimatizing and measuring the moisture content.


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## Loren (May 30, 2008)

If the boards are not quartersawn, cupping in wide stock is
inevitable. All the hullaboo about big resaw capacity is nonsense
unless you are working with quartersawn lumber as instrument
makers do, or need the capacity for stuff like turning.

You will only get flat, consistent veneer or guitar plates from
quartersawn wood in widths over 8" or so. I recommend
ripping boards down to 4" to 5", resawing and jointing. You
will lose far less wood this way than if you try to resaw flatsawn
boards.


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## MikeMD (Apr 13, 2011)

That's very good insight Loren. I'll have to do some experimentation. Resawing and bookmatching was really what drove my bandsaw purchase. I'm trying to work out what I can and can not do.

My worst experiences have been on some 8-10" wide 4/4 walnut. Now I'm trying to figure out what to do with 3' lengths of 10" wide 1/2" cupped walnut. Expensive firewood I suspect.


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## Loren (May 30, 2008)

Rip and joint it.


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## Finn (May 26, 2010)

I solved this problem by keeping the wood to be resawed in my shop for a few days before cutting.


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