Tuning Up A Century Old Dresser - With Roller Guides

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DerbyDad03 wrote:

Quite true if the construction was such that bending could occur. If you glue a 1/4 x 36 x 18 piece of ply across a couple of 2x4s then clamp down the 2x4s and stand on the ply, do you think the ply will bend? I don't.

Also true but it doesn't take years, just a few days. Maybe even less in the winter with the heated house resulting in much lower humidity.
I'm in the process of building an entry door. The glued up panels are 7/8" thick. They were built 3-4 weeks ago during a rather warm, humid spell. It turned cool again and I noticed a couple of days ago that the 26" wide panels had bowed, probably 1/4" - 3/8" belly. No big deal, if they haven't flattened themselves out when I get to assembling stuff I'll just dampen the concave side.
Note that the panels would not have warped if the edges had been constrained; split, maybe, but not warped.

Maybe so but whatever you do won't last unless you correct whatever caused them to warp in the first place. If it were me, I'd just do the best I could and forget it. A bit of belly in a dresser drawer isn't gong to hurt anything; maybe even help if one keeps one's marble collection in it :)
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On 04/11/2016 6:13 PM, dadiOH wrote: ...

Of _course_ it will; it doesn't have an infinite modulus of elasticity; if it were 1/4" steel plate it would still bend; just not quite so much...
Let's see...from FPL Wood Handbook, for plywood
E --> 1.10-1.24x10E5 lb/sq-in
and for a rectangular solid beam the moment of inertia is bh^3/12 where b=width, h=height so for the drawer that's
I*(1/4)^3/12 --> 18/(12*4*4*4) --> 3/(2*4*4*4) = 3/128 =0.02344 in^4
For a constrained beam at both ends, max deflection at midpoint is
ymax=Wl^3/192EI
For a 200 lb load that's
ymax 0*36^3/(192*1.1E6*0.023) = 1.88"
For comparison, E for steel ~27E6 so the deflection would be about 0.07" instead.
...

If you build a panel door that is fully and tightly constrained on all sides with no expansion room, it'll fail sooner rather than later. Door panels in exterior doors are _not_ fixed; they float.
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On Monday, April 11, 2016 at 7:51:10 PM UTC-4, dpb wrote:

I wasn't going to mention the fact that dadiOH wants me to secure the bottom on 3 sides. Aside from all the other reasons that fix won't work, securing the panel on 3 sides is probably a bad idea too.
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dpb wrote:

Gee, I learn something new every day.
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On 04/12/2016 5:55 AM, dadiOH wrote:

You're welcome... :)
OTOH, I don't know why you're now getting snippy; just responded to your comments implying trying to keep a panel flat by constricting the edges...
But, suit yourself.
--



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dpb wrote:

I wasn't trying to be snippy. If I was trying to be snippy, I would have asked, "Float in what?" or "So I can't glue in a plywood bottom?". :)
And I don't think restraining the edges keeps a panel flat. Restraining the top and bottom of the FACES at the edges, yes; edges themselves, no.
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On 04/11/2016 6:50 PM, dpb wrote: ...

BTW, just for comparison, if the ends were free instead of constrained from rotation as was postulated, the maximum deflection is
ymax=Wl^3/48EI
Same form, just the constant turns out different. The deflection would be 4X that of the constrained case (192/48-->4).
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So you're saying there's 1/8" of sag? Based on a prior post where I think you said the sides extend 1/2" below the groove.
I don't think I'd worry about 1/8" of sag.
John
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On 04/11/2016 7:53 AM, John McCoy wrote:

"...the gap between the straight edge and the bottom of the drawer at the center of the bottom."
That's pretty deeply bowed, indeed. Wonder what was in the drawers but 36" is a long unsupported span for what appears to be pretty thin material.
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On Monday, April 11, 2016 at 9:09:52 AM UTC-4, dpb wrote:

I haven't mic'ed the bottom, but it's probably 1/4". I'm not home right now, so that's just a guess.
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On 04/11/2016 8:15 AM, DerbyDad03 wrote:

"mic'ing" is a little overboard... :)
That's what I'd judged from the picture. Couldn't tell for certain if was ply or solid bottom.
I'd still go with the "dampen and weight/wait" ploy first, but was coming back to add that while I know you'd rather keep it original, with that large of a drawer if you really want it to be a functional piece again rather than just collector/display item, it may be that you should consider building new drawer bottoms. If there's some clearance below, in the aforementioned TN shop for SHMBO I replaced failed drawer bottoms with 3/8" solid soft maple stock (rabbeted edge, of course, to fit existing 1/4" groove). Soft maple because it's strong and neutral color/grain and not excessively obtrusively "modern" as a piece of current ply would be.
The alternative is, as also noted elsewhere and by others, use some external stiffener either on bottom or inside the drawer--another ploy in that regard that makes some more significant changes to the piece is to add a middle divider so that you have another support in the middle like the back. That, of course, changes the piece more but can be done without terrible damage so can be (mostly) reversed but would leave signs.
Note to the daughter -- if you do get these unbowed, _nothing_ heavier than the lightest of down pillows can be stored in those wide drawers... :)
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On 04/11/2016 8:59 AM, dpb wrote: ...

BTW, presuming the bottom is still solid but just bowed, you can do the divider trick w/o actually attaching it directly to the front so the modification evidence is minimal if taken out. The bottom is constrained by the groove at the edge and held in place by the brads at the rear plus you can go thru the rear side so when the bottom is brought up to the bottom of the divider it (the divider) can't go anywhere; the bottom has to come up to it. That's for front-to-back; side to side you've got grooves both ends.
For the one I recall specifically did for wife's shop I actually took the bottom out, used a hand router plane and cut a stopped dado for the divider in the front inside and pinned it to add some extra rigidity. It was even wider than yours, though, 42" iirc...was a buffet-like piece, not a dresser.
--




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On Monday, April 11, 2016 at 8:57:14 AM UTC-4, John McCoy wrote:

No, I'm saying there is 3/8" sag on one drawer and 1/2" sag on the other.

I wouldn't either, but that's not what I have.
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On 4/11/2016 9:22 AM, DerbyDad03 wrote:

with the operation of the drawers.
If it's not hurting anything, I'd leave it alone. It took many years to develop, it will take many years to flatten without using lots of force and risking cracking and placing other components under stress. If anybody else even notices it, call it "character" and explain to them how it proves originality and enhances value. It's OLD, it's supposed to be wrinkled.
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OK, think I mis-read your prior post to say you were measuring up from the underside of the drawer.
I am surprised, with 1/2" of sag, that the bottom hasn't pulled out of the grooves in the sides. If that bottom is solid wood, which way does the grain run? Is it possible the wood has expanded due to humidity, and can't fit without bowing?
John
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On Saturday, April 9, 2016 at 8:09:44 PM UTC-5, DerbyDad03 wrote:

Can you easily remove the drawer bottoms and flip them over? If so, then all you'll need to do is (sand smooth? and) apply a finish to the "new" surface.
Sonny
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On 04/09/2016 8:09 PM, DerbyDad03 wrote: ...

As J McCoy notes, they're nailed with brads; this is common construction so the bottom can be replaced if necessary; if all four sides are captured in groove then the only choice is to try to disassemble the drawer itself...anyway, that aside, I'd recommend to _not_ do major structural modifications; two suggestions.
1) use a _tiny_ drop of epoxy in _only_ the nail holes and sufficiently small it won't glob up and glue the bottom to the rear drawer bottom and re-nail. I've had success if the drawers aren't subsequently drastically overloaded in that the epoxy will hold the nail but you've not ruined any chance of removing them for repair/replacement of the bottom later by gluing the bottom itself...
2) there are only three (or maybe there's a fourth towards the left; unclear from picture for certain) brads shown; whether that's all there were or that's all there are left, having lost a couple of others, the obvious fix in the vein of the original is to add a couple new ones in fresh wood locations. I'd probably add a second near the existing and then insert new between present locations.
Btw, the knob kickers can usually be fixed by a strategic insert of a small patch inserted in the necessary location to provide a new "bite" surface. I didn't look at all the pictures but have had a number of these in the past when the SHMBO ran a small antiques booth in TN and worked over a lot of pieces for her...that was a "trick" taught me by Lonnie Bird in one of his seminars many, many years ago, now... :)
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On 04/10/2016 9:57 AM, dpb wrote: ...

_IF_ it were to be considered necessary to add some mechanical fix, one alternative that is mostly reversible I've used is to add a small quarter-round on the inside, fastened with brads but no glue. Going at 90-deg angle to bottom and back gives quite a lot of strength with very small brad/pin and leaves minimal residual damage if removed...and drawer is still repairable going forward.
Start throwing new glue in places where it isn't precludes any further repair that can't happen 'cuz can't safely remove the glue plus if one does want to try to retain what value there is in the piece on any future antiques market, those kinds of repairs will knock it out of the collectible class immediately into just old furniture...
--


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On Sunday, April 10, 2016 at 10:58:18 AM UTC-4, dpb wrote:

Securing the back of the bottom to the back of the box may take care of the sag from left to right, but the bottoms have actually taken on kind of bowl shape.
Flattening the back by securing to the box hardly removes any of the center sag.

For now I used the standard glue and toothpick methods and I was able to crank the bolts down really tight.
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On 04/10/2016 12:05 PM, DerbyDad03 wrote: ...

Well, you didn't provide sufficient info to know about it, either... :)
The question becomes one of how much you're willing to sacrifice from original; another mentioned one option similar to that which I outlined above which isn't _too_ obtrusive.
No dimensions given; depending on just how wide they are, I've had some success in the past if they are solid material in dampening and weighting as dry to reform them but that's a hit 'n miss proposition. The one thing of it is that it basically is a no-cost/no-foul thing to try as long as there's not veneer to lift.
Other than that, you can try simply the "invert and weight" (and wait) technique.
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