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Forum topic by jmack77 posted 03-19-2012 09:12 PM 956 views 0 times favorited 11 replies Add to Favorites Watch
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jmack77

29 posts in 1821 days


03-19-2012 09:12 PM

Here’s what I’ve got. I’m trying to mill some 4/4 oak for a project for work. I rough cut the lumber to 3 3/4 inches by 48 inches. I ran all the pieces through the jointer until I had a nice flat face. There was a slight bow to the boards, so I made sure that I had the bow pointed down when I put it through the jointer. Then I ran the pieces through the planner. And that’s where I ran into a problem. I noticed that some of the boards got a bow to them. What has got me stumped is that the bow is now reversed. The face that I ran across the jointer had the bow pointed down, now it is pointing up. I’m pretty sure this is being caused by the stress being relieved by the planning.

So my questions are these:

1. Am I right in thinking that the bow is being cacused by the stress?
2. I got the wood planned down to 7/8”, so I’ve got 1/8” to work with. Any helpful hints on how get these boards flat?


11 replies so far

View map's profile

map

85 posts in 2262 days


#1 posted 03-19-2012 09:40 PM

Check the moisture in the boards. It sounds like you may have had a dry exterior with a wetter interior on the boards. I would likely leave them in the shop for a couple of weeks to let them settle before doing any more milling. I just got through replacing all of the drawer fronts on a 8-drawer file cabinet because of a similar problem.

-- measure once, cut once, swear, start over

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jmack77

29 posts in 1821 days


#2 posted 03-19-2012 09:53 PM

Thanks Map. Crap. I really wanted to build these doors tomorrow, and get this cabinet finished.

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pintodeluxe

3559 posts in 1562 days


#3 posted 03-19-2012 10:08 PM

I like Tommy Mac’s method of rough jointing and rough planing, then stack and sticker the stock for a day or two. Then come back and finish mill it. Make sure you are running the boards concave side down across the jointer, otherwise they will never flatten out. As far as the planer, if it goes in like a bananna, it will come out like a bananna.
Other causes include uneven moisture or temperature from one side of the board compared to the other side. Finally, you occasionally will run into reaction wood. This is wood that will spring into a curved shape when you mill it. This can be caused by kiln drying the lumber too hot, or just by releasing tension from the wood fibers. Crotch wood is prone to being reaction wood, as is wet or green wood.
Let it dry a bit, and re-mill it. Maybe it can be saved.

-- Willie, Washington "If You Choose Not To Decide, You Still Have Made a Choice" - Rush

View MoshupTrail's profile

MoshupTrail

299 posts in 1229 days


#4 posted 03-19-2012 10:19 PM

Definitely leave it sit for at least 2 weeks. In an attic if you can – it will act like a solar kiln. But, also look at the grain direction. If you’ve got flat sawn boards, they are much more likely to do this than quarter sawn or rift sawn.

-- Some problems are best solved with an optimistic approach. Optimism shines a light on alternatives that are otherwise not visible.

View WDHLT15's profile

WDHLT15

1213 posts in 1224 days


#5 posted 03-20-2012 02:25 AM

I also think that you have a moisture issue.

-- Danny Located in Perry, GA. Forester. Wood-Mizer LT15 Sawmill. Nyle L53 Dehumidification Kiln. hamsleyhardwood.com

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Trapshter

62 posts in 1142 days


#6 posted 03-20-2012 03:42 AM

I second pinto and map.

-- Smile and wave boys just smile and wave

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jmack77

29 posts in 1821 days


#7 posted 03-20-2012 11:57 PM

Thanks for the info guys. I guess I’ll stack in the garage for a few weeks and see how it is then.

View fussy's profile

fussy

980 posts in 1799 days


#8 posted 03-21-2012 06:22 AM

Jmack,

The lesson is never mill stock to the needed dimension in one fell swoop. Do mill part way (after having allowed it to acclimate in the shop for a couple weeks), then let it sit for a week or two (especially very hard woods that in my experience tenf to behave badly at first), then creep up on it in a couple more steps over a couple days. This is one place where it doesn’t paY TO be in a hurry. There are probably others—oh, heck, never get in a hurry period. Hope they settle down for you.

Steve

-- Steve in KY. 44 years so far with my lovely bride. Think I'll keep her.

View Loren's profile

Loren

7823 posts in 2396 days


#9 posted 03-21-2012 06:54 AM

Removing wood takes away stress in an unbalanced way and also
exposes a new surface to moisture and drying. The wood may
relax to straight or close to it. This is part of why hand planes
and a bench for using them are an asset – because you can make
minor corrections in the milling process that are impractical and/or
wasteful due to the geometry of the jointer and operator error
in both assessment of board geometry and feeding.

You’re getting a crash course in milling. Pay attention to the
wood at hand.

-- http://lawoodworking.com

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HalDougherty

1820 posts in 1985 days


#10 posted 03-21-2012 10:56 AM

jmack77,

Stacking your lumber in the garage is a good idea, but not the best. The best suggestion you have been given in the posts above is to stack it in your attic where it will heat up in the daytime and cool at night. Plus if you have a heat pump, you are removing moisture from the air as well. The gentle solar kiln style drying that’s taking place will dry your wood and at the same time condition it. You read a lot about drying lumber, but almost nobody talks about conditioning the wood to relieve stress and prevent honeycomb or case hardening. I dry wood for gunstocks and my wood must be both dry and stable. It was 80 degrees here today and if it stays this warm, my 1” thick rough stock will dry to 20% moisture content in 30 days outside, and to between 6 & 12% in 30 days in my attic. Plus after it’s dry, I can resaw the 1” thick lumber into thinner sections to use to laminate gunstocks and they won’t cup, twist or bow after I plane them and sand them. If they are dry, but dried too fast or not stress relieved by cooling cycles, they can bow, twist and cup like crazy. That’s why I stopped buying kiln dried hardwood a long time ago.

-- Hal, Tennessee http://www.first285.com

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jmack77

29 posts in 1821 days


#11 posted 03-21-2012 07:02 PM

Thanks again for all the info guys. One thing that I’ve been having a hard time trying to get a handle on is “letting the wood acclimate to the shop”. I live in the Eastern Panhandle of WV, so our climate goes from being dry in the winter, to really humid in the summer. My “shop” is our two car garage that had insulated walls but an un-insulated garage door. For climate control I have a window AC for the summer and a space heater for the winter. The way our house is, the garage has become the main entry point to our house for the wife and kids. So it would be really hard to have the AC unit or space heater running the whole time, especially when I’m not out there.

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