LumberJocks

All Replies on Walnut slab cupping after flattening?!

  • Advertise with us
View Tishman's profile

Walnut slab cupping after flattening?!

by Tishman
posted 08-30-2016 04:42 PM


20 replies so far

View RRBOU's profile

RRBOU

176 posts in 2652 days


#1 posted 08-30-2016 04:50 PM

I am guessing that you laid them on the bench, the under side did not get any air and this is why thy cupped. It is very important to after removing thickness to let air get to both sides.

-- If guns cause crime all of mine are defective Randy

View Aj2's profile

Aj2

2199 posts in 2158 days


#2 posted 08-30-2016 05:02 PM

It could be several reasons.like RRBOU mentions they didn’t acclimate evenly.
Or it could be the slab has tension in it.If you look at the sides can you see the way the grain runs.Does it match the cupping.
Or is there a oval cathedral grain on the surface that matches the cupping.
These are the most common one that I find.

Aj

-- Aj

View gargey's profile

gargey

1013 posts in 1136 days


#3 posted 08-30-2016 05:03 PM

Higher than usual neutrino shower last few days could have contributed.

View soob's profile

soob

270 posts in 1569 days


#4 posted 08-30-2016 05:53 PM

2” lumber that shows 7% on the outside might be 20% in the center. Thick slabs take a long time to dry.

View Robert's profile

Robert

3370 posts in 1841 days


#5 posted 08-30-2016 06:05 PM

Big checks and splits indicate internal stress.

or what he ^ said.

-- Everything is a prototype thats why its one of a kind!!

View Tishman's profile

Tishman

16 posts in 1170 days


#6 posted 08-30-2016 06:13 PM

Thanks, everyone!

@RRBOU you are correct. I flipped it and it seems to be flattening back out. If it flattens back out, can I continue working on it (belt sanding, finishing, etc.) and just leave it on its edge when not working it?

View WDHLT15's profile

WDHLT15

1816 posts in 2836 days


#7 posted 08-31-2016 12:51 AM

Yes, you need to let it get air on all sides. I suspect that the slab is not as dry as you think it is, as a dry slab would not cup.

-- Danny Located in Perry, GA. Forester. Wood-Mizer LT40HD35 Sawmill. Nyle L53 Dehumidification Kiln. hamsleyhardwood.com

View mahdee's profile

mahdee

4285 posts in 2128 days


#8 posted 08-31-2016 10:44 AM

Instead of putting it on its edge, put some 2×4s under it.

-- earthartandfoods.com

View dbray45's profile

dbray45

3320 posts in 3137 days


#9 posted 08-31-2016 12:43 PM

One of the problems with walnut is the stress. I have had blades stop from the stress locking on the blade and pieces fly off when cutting. Watch the grain carefully.

I had a local mill (he moved away) that kiln dried everything. For the big stuff, he would let it sit for 2 years – covered from the elements and stickered to dry before putting it in the kiln. Since he moved away, all wood that I get, I let it sit in my basement for 2 months with a dehumidifier running 24×7. This has worked well.

-- David in Damascus, MD

View dbray45's profile

dbray45

3320 posts in 3137 days


#10 posted 08-31-2016 12:49 PM

If it doesn’t flatten out, and you are not in AZ, lay it on the ground, cup side down for a few hours. It will pull moisture from the ground on that side.

If it is white oak the rules are different. This wood can take up to 4 times longer for slabs to dry.

-- David in Damascus, MD

View Tishman's profile

Tishman

16 posts in 1170 days


#11 posted 08-31-2016 03:02 PM

Thanks everyone! Slab has started to flatten back out. Will keep it on 2X4s on the bench while working on it, installing bowties, sanding, etc. Appreciate all the advice!!

View KelleyCrafts's profile

KelleyCrafts

3701 posts in 1099 days


#12 posted 08-31-2016 03:24 PM



If it doesn t flatten out, and you are not in AZ, lay it on the ground, cup side down for a few hours. It will pull moisture from the ground on that side.

If it is white oak the rules are different. This wood can take up to 4 times longer for slabs to dry.

- dbray45

Cause in AZ our wood is dry 10 minutes off the tree. Instant kiln dried wood here! ;)

-- Dave - http://kelleycrafts.com/ - pen blanks - knife scales - turning tools

View dbray45's profile

dbray45

3320 posts in 3137 days


#13 posted 08-31-2016 07:21 PM

Yep – setting it on the ground in the sun will scorch it.

-- David in Damascus, MD

View Tishman's profile

Tishman

16 posts in 1170 days


#14 posted 09-05-2016 07:11 PM

Thanks again, everyone. I reflattened both sides. It’s at about 13% moisture content. Should I put it on 2×4s and clamp it to the workbench so it won’t cup or what? Please advise!

View Logboy's profile

Logboy

75 posts in 3590 days


#15 posted 09-10-2016 03:54 AM

You need to stop working on it and wait until the dang thing is dry or you’ll just be chasing your tail. It will continue to just cup and warp until it finally reaches 6-8% moisture.

View newwoodbutcher's profile

newwoodbutcher

794 posts in 3210 days


#16 posted 09-10-2016 04:23 AM

What he said

-- Ken

View daddywoofdawg's profile

daddywoofdawg

1028 posts in 1935 days


#17 posted 09-10-2016 10:37 AM

sticker it and put it away for a couple months.it needs to dry,and relax after you flatten it.

View unbob's profile

unbob

810 posts in 2264 days


#18 posted 09-10-2016 03:12 PM


One of the problems with walnut is the stress. I have had blades stop from the stress locking on the blade and pieces fly off when cutting. Watch the grain carefully.

I had a local mill (he moved away) that kiln dried everything. For the big stuff, he would let it sit for 2 years – covered from the elements and stickered to dry before putting it in the kiln. Since he moved away, all wood that I get, I let it sit in my basement for 2 months with a dehumidifier running 24×7. This has worked well.- dbray45

This is worth repeating, I have been working some really nice local walnut. I have had some incidents where pieces have broken off, and kicked back out. Best not to stand in front of the blade!

View Gene Howe's profile

Gene Howe

11490 posts in 3789 days


#19 posted 09-10-2016 05:40 PM


Cause in AZ our wood is dry 10 minutes off the tree. Instant kiln dried wood here! ;)

- ki7hy

You said it. Where are you?

-- Gene 'The true soldier fights not because he hates what is in front of him, but because he loves what is behind him.' G. K. Chesterton

View Tishman's profile

Tishman

16 posts in 1170 days


#20 posted 09-14-2016 03:05 PM

Understood and thanks for the advice. It’s in the attic, where it’s about 20% lower humidity and 20° hotter than the rest of the house stickered and weighted. I’ll check in periodically. Thanks everybody!

Have your say...

You must be signed in to reply.

DISCLAIMER: Any posts on LJ are posted by individuals acting in their own right and do not necessarily reflect the views of LJ. LJ will not be held liable for the actions of any user.

Latest Projects | Latest Blog Entries | Latest Forum Topics

HomeRefurbers.com