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Can I straighten this out?

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Forum topic by splinterking posted 10-01-2014 03:00 PM 1292 views 0 times favorited 15 replies Add to Favorites Watch
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splinterking

67 posts in 1500 days


10-01-2014 03:00 PM

Hi I wondering if anybody has any suggestions on my latest workshop blunder. I’m not sure exactly why this happened ,but the built in cabinet I’m building has a flatness problem. See image below:

This is a front view of the carcass. The black lines represent were things should be and the red where they are. I’m using A1 grade ply from a good dealer in my area, so I don’t think thats whats causing the waviness in the shelves. My guess is that the bottom dado that joins the two shelves at the center divider was a little to tight and might caused kind of wedge effect when I “persuaded” it in place, pushing out on the walls of the dado and that got displace throughout the peice.

The warping isn’t that noticeable, but my concern is when I attach the face frame, I’d like it to be flush with the upper shelf and putting a straight edge to it shows that it will not be as it is. I am attaching a 4” base to this piece so I’m think that may help straighten it out.

My questions are 1. Will the face frame help straighten this any if attached properly and 2. Does anybody have any other ideas to straighten this out.

Also just FYI the cabinet is long about 72”. Thanks for any help!

-- "Clothes make the man. Naked people have little or no influence on society." ~Mark Twain


15 replies so far

View timbertailor's profile

timbertailor

1592 posts in 887 days


#1 posted 10-01-2014 03:08 PM

You can cut biscuit joints in the shelves and align them with the face frame to straighten them out.

Not really a big deal if you are going to install drawers. The face frame should provide enough clearance to overcome any bowing.

A torsion box would have been my recommendation to prevent bowing.

-- Brad, Texas, https://www.youtube.com/user/tonkatoytruck/feed

View Earlextech's profile

Earlextech

1159 posts in 2153 days


#2 posted 10-01-2014 03:40 PM

Put a square back and a front on it and call it a day.

-- Sam Hamory - The project is never finished until its "Finished"!

View MT_Stringer's profile

MT_Stringer

2853 posts in 2694 days


#3 posted 10-01-2014 03:41 PM

I ruined a cabinet similar to yours because i cut the middle support a little short, then once glued, persuaded to gaps in the dadoes to close up. No face frame correcting. The shelf wouldn’t line up. I finally took a circular saw and cut it in two pieces! Part of the cabinet is hanging on my wall in the shop. The other piece is in the guest bathroom, trimmed out. With dark stain and towels stacked on the shelves, the defects are not noticeable.

I know how you feel about expensive plywood. Mine was maple and it broke my heart to cut it up.

-- Handcrafted by Mike Henderson - Channelview, Texas

View pintodeluxe's profile

pintodeluxe

4854 posts in 2276 days


#4 posted 10-01-2014 03:48 PM

Is it already glued up? If not, widen the dado slightly with a sanding block. If it is already glued, then you will have to see if it can be corrected with a face frame and base lumber. Since both the upper and lower shelves have deflected upwards, I think you can fix it. 1+ Brad’s recommendation to use biscuits and a face frame.
I like the drawing. A picture of the actual project may help too.

Good luck.

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

View mudflap4869's profile

mudflap4869

1155 posts in 922 days


#5 posted 10-01-2014 04:03 PM

A relief kerf opposite the dado might allow it to return to level. You might have to cut completely through to the center piece to relieve the pressure. Since it will be attached to a base, it shouldn’t lose very much structural integrity.

-- Still trying to master kindling making

View splinterking's profile

splinterking

67 posts in 1500 days


#6 posted 10-01-2014 04:36 PM

Hey thank you everyone for your assistance! I had thought along the same lines as timbertailor using biscuits, but I wasn’t sure if it would work. Also mudflap I like the idea of the relief cut. I think I can get there now. I will put the base on tonight and see what happens, might make the base a pseudo torsion box to help maintain flatness.

Its nice to have this forum of friendly folks to share ideas with. I’ve asked my Australian Shepherd who tends to help out in the shop what he thought the solution was, but he didn’t have any ideas : )

-- "Clothes make the man. Naked people have little or no influence on society." ~Mark Twain

View JAAune's profile

JAAune

1642 posts in 1780 days


#7 posted 10-01-2014 05:31 PM

It is usually a lot easier to build a face frame then attack the carcass panels. That makes it easy to get everything straight. Plywood is never straight either and it flexes a lot during assembly.

To fix the problem, use biscuits or pocket holes to firmly attach the plywood to the face frame every few inches to keep it lined up where it needs to be.

-- See my work at http://remmertstudios.com and http://altaredesign.com

View BinghamtonEd's profile

BinghamtonEd

2281 posts in 1832 days


#8 posted 10-01-2014 05:52 PM



It is usually a lot easier to build a face frame then attack the carcass panels. That makes it easy to get everything straight. Plywood is never straight either and it flexes a lot during assembly.
- JAAune

I always used to think the opposite. Then I read a book from the publishers of FWW that detailed the process, from making the frame, cutting the grooves, installing the sides and then the top/bottom. It suddenly seemed to make sense. Next casework project I do, I’ll do this way, to see how I like it. Coincidentally, I just added a bookcase project, and I did the case first. I added the faceframe and ended up with a little warp in the plywood that made the case stick out past the frame about 1/32 at one point, I was able to pull it back in with pocket screws. But, if I had built the frame first, it would have been pulled flat at initial assembly. I read the chapter on frame-first casework maybe 3 days after that incident.

-- - The mightiest oak in the forest is just a little nut that held its ground.

View dhazelton's profile

dhazelton

2324 posts in 1759 days


#9 posted 10-01-2014 06:21 PM

Over a 6 foot span I’m sure your face frame or the plywood back will allow you to pull that center down.

View splinterking's profile

splinterking

67 posts in 1500 days


#10 posted 10-01-2014 06:42 PM

@BinghamtonEd, reading about how to do something better right after you do it wrong is usually how I do it too.

-- "Clothes make the man. Naked people have little or no influence on society." ~Mark Twain

View Rayne's profile

Rayne

470 posts in 1002 days


#11 posted 10-01-2014 07:00 PM

I just re-read this. If this is a Built-in cabinet, couldn’t you just screw the cabinet into the cavity and force it flat? I guess that would be dependent upon the kind of niche it’s going in.
Otherwise, make a back and nail/screw it in square. The face frame will help keep it straight.

View Loren's profile

Loren

8302 posts in 3111 days


#12 posted 10-01-2014 07:35 PM

I might do something like joint a 2×4 straight and screw
it to the bottom to straighten it out. If you want
the “deck” flush or ever-so-slightly proud of the
face frame edge the 2×4 trick may pull it in straight
enough to attach the face frame. It’s possible
a “sprung jointed” 2×4 may be needed. Once the
face frame is solidly attached, unscrew the 2×4.

View Nubsnstubs's profile

Nubsnstubs

826 posts in 1193 days


#13 posted 10-01-2014 08:54 PM

Is that 4” base a plinth, or a toe kick?

Are your ends finished or is this cabinet going between walls?

When you say top shelf, is that the box top you’re talking about? It’s just a fancy box.

Your picture shows a bow, but exactly how much bow is there.? Under 1/8” can be pulled into straight with both Face Frame and back.

I was self employed for 40 years building cabinets and furniture. Whenever I had a problem like what you are showing, it was usually in the dado depth and or the devider length. Sometimes when it bowed like that and all dimensions were correct, it would be the devider cut out of square.

I have always made my Face frames first because I always and still use dowels. Just the way I learned. After the FF is built, check to see it fits the opening or space availible, then cut up the other stuff to fit the face frame.
I think I used ‘affix” too many times…..... Jerry (in Tucson)

Assemble the carcass, glue the front edge of the carcass and then lay the face frame onto the glued edge. Start affixing the FF using whatever method of holding you intend to use to hold the face frame in place while adjusting the ff to be flush where it is intended to be flush. Repeat affixing until the FF is attached, then clamp it for 30 minutes. After 30+ minutes, remove all clamps, turn it over to affix the back. If the back is square and the same size as the carcass, when affixing it, it should take care of any descrepancies you might have.

-- Jerry (in Tucson)

View splinterking's profile

splinterking

67 posts in 1500 days


#14 posted 10-01-2014 09:14 PM

@Nubsnstubs, the base is a plinth, it is going between walls in to a recess. I’m not sure how much bow there is exactly, but I’d guess between a 1/8 and a 1/4” I’m actually putting a separate top on, above the lines you see in the picture. I have to scribe in the on three side to make it flush, so I’m attaching it after I get the FF scribed in.

-- "Clothes make the man. Naked people have little or no influence on society." ~Mark Twain

View firefighterontheside's profile

firefighterontheside

13466 posts in 1319 days


#15 posted 10-01-2014 09:26 PM

Not too surprising for plywood to have a little bow to it like that. If you used pieces that were both bowed the same way then the total piece will have a bow. You could have installed pieces so as to have one piece bowed one way and the other bowed opposite and then the total would have been more straight. Usually my stuff has back panels that straightens everything out for me. If I’m making something without a back panel and it mounts on a wall, I have a cleat for mounting and I can straighten it out as I’m mounting it. Attach both ends and then pull the middle down and screw it to the wall.

-- Bill M. "People change, walnut doesn't" by Gene.

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