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straighten warped pkywood-after you fix it does it stay like that when it gets dry again?

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Forum topic by MiniMe posted 01-26-2020 10:47 PM 746 views 0 times favorited 9 replies Add to Favorites Watch
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MiniMe

384 posts in 682 days


01-26-2020 10:47 PM

I am starting to build the workbench I have posted about a while ago
So I bought the 2×4s and a sheet of pine plywood (4×8) cut in half along the long side by the HD guy
I am now seeing better that the plywood is not perfectly straight and Google is telling me that it can be straighten by adding moisture to the concave part (not sure in inside or outside) They say it gets back to normal.
Now..since my design requires the top to be free standing (so I can lift it when I need) I am wondering what happens when the plywood gets dry again…
Is this the best method to straighten it ? If it goes back to warped again how can I stop that (please see the above pointed to topic for my design, have that in mind when you post your advice)

thank you
MM


9 replies so far

View controlfreak's profile

controlfreak

449 posts in 232 days


#1 posted 01-26-2020 11:00 PM

Plywood and water never mix well. I think you will need some sort of frame to attach the plywood to, to straighten it out. You may want to take two sheets and glue and screw them together to let each firm up the other but when you do it they will need to be flat.

View Madmark2's profile

Madmark2

829 posts in 1219 days


#2 posted 01-27-2020 01:38 AM

The moisture causes the glue between the plies to slip. Once it moves, you’re done. You might be able to screw it flat but the sheet will never be the same.

-- The hump with the stump and the pump!

View Robert's profile

Robert

3626 posts in 2111 days


#3 posted 01-27-2020 02:46 PM

You’ll never get it straight no matter what you do.

If you’re laminating the two pieces together, glue them with opposing bows to balance out the forces and it will be pretty flat.

This is a common problem buying plywood at HD. Next time you go, take a look at the racks and how the ply is supported and you’ll see why it is often bowed.

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

View Axis39's profile

Axis39

158 posts in 228 days


#4 posted 01-27-2020 03:48 PM

I usually move the first three to five pieces off a stack if I’m buying plywood at Home Depot or Lowes. I dig until I get the flattest pieces. I do the same with any wood I buy there… I dig and sight every piece.

But, since you already have the plywood, I agree that it’s time to build a frame for your top.

-- John F. SoCal transplant, chewer uppper of good wood

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Axis39

158 posts in 228 days


#5 posted 01-27-2020 03:49 PM

I usually move the first three to five pieces off a stack if I’m buying plywood at Home Depot or Lowes. I dig until I get the flattest pieces. I do the same with any wood I buy there… I dig and sight every piece.

But, since you already have the plywood, I agree that it’s time to build a frame for your top.

-- John F. SoCal transplant, chewer uppper of good wood

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controlfreak

449 posts in 232 days


#6 posted 01-27-2020 06:16 PM

I too have to move the first three pieces which is hard for me with my bad shoulders and general arm weakness that I am trying to figure out. I do a gym workout every other day so it’s not from sitting around.

They stack it like that every single time. Some stacks are placed on uneven supports so even a good stack can turn bad. When I store them I clamp several sheets together to limit the tendency to warp. I think my next shop project is going to be a scrap wood and sheet goods cart. That has me thinking something. Do any of you LJ halve your sheets right away or let them stay whole and nibble off what you need? I have a small shop and it is not easy to keep full sheets around.

View MiniMe's profile

MiniMe

384 posts in 682 days


#7 posted 01-27-2020 08:56 PM

Yes I could see the problems but there was not much I could do
The stack had just 3-4 of them stored higher and difficult to get so I had to ask an employee to help me but even so there where like 4 of them left …
There is lots if info showing it can be done
https://www.google.com/search?q=straighten+plywood
not sure why there is so much misleading info

View sansoo22's profile

sansoo22

625 posts in 285 days


#8 posted 01-27-2020 10:02 PM


not sure why there is so much misleading info

- MiniMe

Because its a statistical fact that half of the human population is dumber than the other half. The top half is usually too busy fixing the problems caused by the bottom half to have time to post in depth information on the internet.

Also blame advertising. That alone gives lots of run of the mill folks incentive to start a blog or a YouTube channel and get followers so they can increase exposure which in turn gets them more views and more ad dollar revenue.

So advertising ruined the internet.

I have had some luck with stickering smaller plywood pieces and tossing a floor fan on it overnight. The warping wasn’t completely gone but it made it good enough to use.

ControlFreak – I typically dont store full sheets. I bring home what I need for a project and even if i wont be getting to it right away break it down into rough stock, label it, and store it on my plywood cart.

View MiniMe's profile

MiniMe

384 posts in 682 days


#9 posted 01-28-2020 01:09 PM

I kind of stay away of this type of broad generalizations as I found myself dumb in many respects (just because I am not educated in that particular domain) No matter how intelligent you are you will not be able to grasp all the aspects of a situation requiring skills in a certain domain and, inevitably you will take dumb decisions which puts you in one of the halves you mentioned below. Think about it :-)

I have not extensively researched the sources for all that info saying it is possible because I decided to screw the top to the frame

not sure why there is so much misleading info

- MiniMe

Because its a statistical fact that half of the human population is dumber than the other half. The top half is usually too busy fixing the problems caused by the bottom half to have time to post in depth information on the internet.

Also blame advertising. That alone gives lots of run of the mill folks incentive to start a blog or a YouTube channel and get followers so they can increase exposure which in turn gets them more views and more ad dollar revenue.

So advertising ruined the internet.

I have had some luck with stickering smaller plywood pieces and tossing a floor fan on it overnight. The warping wasn t completely gone but it made it good enough to use.

ControlFreak – I typically dont store full sheets. I bring home what I need for a project and even if i wont be getting to it right away break it down into rough stock, label it, and store it on my plywood cart.

- sansoo22


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