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Mahogany internal stress?

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Forum topic by JimYoung posted 07-07-2016 12:29 AM 527 views 0 times favorited 6 replies Add to Favorites Watch
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JimYoung

227 posts in 1050 days


07-07-2016 12:29 AM

Topic tags/keywords: question mahogany planer milling

Hi All,

Today I picked up some 5/4 African Mahogany at the local mill. I’m working on a small project and will be gluing up a panel 1/2” thick x 12” x 24” to cut some blanks for a small project. The board I picked up was pretty straight, has nice grain, and was quarter sawed.

I cut down the board to 24” lengths, and I used my planer sled and milled one face flat and then planed the other face. Next I ripped the boards to ~2 1/4” widths. I had some trouble with this and lucky I have a splitter on my table saw, since the board wanted to close in on the blade. I cleaned up the edges, and now I have a stack of 1 1/8”x 2 1/4” x 24” boards. Next I’m going to rip the boards down to 1/2” thickness. On the first board I tried to rip it in one pass, but it bound up the blade. So I lowered the blade and made one pass about 1 1/2” deep and then went to the band saw to separate the boards.

I finish planed the boards to clean up the saw marks and ended up with slightly less than 1/2” thick planks. The problem now is that all the boards have a 1/8” to 1/4” matching bow in them. Each book matched board bowed in the opposite direction.

Here’s the question, can I still glue up this panel if I alternate the boards with bow up and the bow down? I’ll need to use a few culls to clamp the boards flat during glue up. Should this straighten out the panel, or will I just be asking for trouble?

I’ve never seen this working with cherry, oak, or walnut. Is this something specific with Mahogany?

Thanks for your help,

-- -Jim, "Society is well governed when its people obey the magistrates, and the magistrates obey the law." -- Solon


6 replies so far

View Aj2's profile

Aj2

689 posts in 1261 days


#1 posted 07-07-2016 02:10 AM

You just never know till you start cutting how any wood will behave.Even quarter sawn can do weird stuff.
I think if you glue the panels up with a bow they probably are going to twist.But if you can get them in the frames quick enough make you can use them.
Can you use the wood for something else?If not then there’s nothing to lose other then money.
You probably didn’t do anything wrong milling.
Maybe next time let them sit in your shop longer.

View bobasaurus's profile

bobasaurus

2667 posts in 2647 days


#2 posted 07-07-2016 05:10 AM

I’ve had that same problem with African Mahogany. It just doesn’t want to stay straight after ripping. It is soft and flexible though, so you can fix a lot with clamping pressure. I would try to re-joint an edge and re-rip some of the bow out first, though.

-- Allen, Colorado

View JimYoung's profile

JimYoung

227 posts in 1050 days


#3 posted 07-07-2016 03:54 PM

Thanks for the help guys. Since I already have the wood milled down, I might as well see if clamping can straighten them out. I’ve got them glued up now with several culls. I’ll let you know what happens.

-- -Jim, "Society is well governed when its people obey the magistrates, and the magistrates obey the law." -- Solon

View rwe2156's profile

rwe2156

2192 posts in 943 days


#4 posted 07-07-2016 04:13 PM

Since is was 1/4 sawn, I would assume it was internal stresses, moisture, BUT, whenever you resaw you can expect a lot of movement because youre opening up the middle of the board.

I usually put the resawn boards in stickers and clamp them between two large cauls, like a 2×6, and leave for at least 3-4 days in a climate controlled area before milling.

Won’t prevent all movement, but I think it does help.

Then joint/plane/repeat not taking too much off each side equally (like 1/16”).

In your situtation, I would say try a spline and alternate bows. Good luck!

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

View JimYoung's profile

JimYoung

227 posts in 1050 days


#5 posted 07-16-2016 06:50 PM

Hi guys,

Thanks for the advise. I ended up gluing up the panel alternating the bowing up and down with 4 culls to align the boards. The resulting panel was flat and I cleaned it up in my planer. I stickered the panel and have 30 lbs holding it flat while I finish up some other projects. It looks like it will stay flat.

Thanks jocks

-- -Jim, "Society is well governed when its people obey the magistrates, and the magistrates obey the law." -- Solon

View jmos's profile

jmos

736 posts in 1832 days


#6 posted 07-17-2016 12:24 AM

I’m starting a project in cherry; had a nice 8” wide, 68” long, 5/4 board that was pretty flat (2s2 from the lumberyard, they don’t sell rough.) Since my jointer is 6” I had to rip the board in half. After going through the saw, ‘boing’, both boards have a 1/4” bow. Had to skip them for the part I was planning. I’ll try to mill them to 3/4” stock for another part, but if they keep moving, they may be relegated to really small parts. I’ve had similar experiences with poplar too.

Glad you were able to work around your issue.

-- John

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