How much should I account for expansion/contraction? - Woodworking Talk - Woodworkers Forum
 
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post #1 of 7 Old 10-13-2015, 05:18 PM Thread Starter
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How much should I account for expansion/contraction?

Hello all. I am definitely on an amateur level when it comes to woodworking but aspire to be more and have really only done a few small projects. I recently started a project for my sister inlaw several months late that needs to be finished this weekend.

She is a librarian and is having a baby due late this month. My wife (her sister) had an idea to make a baby changing table out of a card catalog. These things are not cheap even in poor condition. We bought the one shown in my first picture for a hefty price. Turns out, in order to have usable drawers large enough for things like diapers and blankets etc, I needed to build it all from scratch since we had a vision of trying to salvage the 15 individual drawer look I soon found it was not doable with what I had. So bought all the wood I needed and went to work. It will be painted so most of it is Aspen and some pine/birch for the drawers. Pic number 2 shows what I have so far, the rest you will have to use your imagination.

In order to mimic the 15 individual drawers that I will reattach the hardware to I will attach individual pieces (2 wide, 3 high on left and 3 wide and 3 high on right) the finishing nails and glue custom cut to fill the whole area (6 total on the left drawer and 9 on the right). I will have thin pieces running down the center of the left and 2 evenly divided on the right to give the look of dividers. So naturally tolerances need to be real tight to keep the look. What you see in pic # 2 is the drawer front backing that will actually be attached to the drawer itself. There is about a 1/16" (2mm) roughly around the drawer front to the inside of the changing table surrounding. My question is: using nice dried Aspen wood, how much can I expect the face to expand/contract? I would hate for her to not be able to open/close the drawers after a few seasons. If it matters this is upper midwest (IL)

Thanks for reading, I look forward to your help.


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post #2 of 7 Old 10-13-2015, 07:04 PM
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tj,

Hopefully this calculator will give you an idea to your answer. http://www.woodworkerssource.com/movement.php
This might help a bit also. http://www.thisiscarpentry.com/2010/...wood-movement/

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post #3 of 7 Old 10-14-2015, 02:05 AM
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As per this dude:
https://woodgears.ca/wood_grain/shrinkage.html

Shrinkage of a board is about 1% across the grain for plainsawn boards, with shrinkage along the grain being so small you dont need to worry about it, if im reading everything right . Put in laymans terms, a 1 inch wide board can be expected to expand and shrink .01 inches across its grain (1*.01), and a 6 inch board can be expected to change by .06 inches, or roughly 1/16 an inch (6*.01).

It should also be noted that seasonal dimensional changes can also be influenced by the cut of the board. Plainsawn lumber, with the grain on the end grain running side to side, will display the most change, whereas quartersawn lumber, with the end grain running vertical, is much more dimensionally stable.

Hope all this helps!

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post #4 of 7 Old 10-14-2015, 08:32 AM
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The species or wood is a major factor in expansion and contraction.

You can have the 15 drawer "look" without actually having 15 drawers.

I am guessing that you will be making this table a normal size. I will further guess, that unless you are super accurate in your cuts, that normal tolerances will take care of any binding.

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post #5 of 7 Old 10-14-2015, 01:29 PM Thread Starter
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Thank you all!

So it seems i need to be more concerned about shrinking than expanding. I am worried the drawers will not open over time.
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post #6 of 7 Old 10-14-2015, 03:51 PM
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No, not necessarily. Shrinkage vs expansion primarily depends upon the environment of the wood. Was it in a moist or dry environment when it was built. Will it live in a moist or dry environment.

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post #7 of 7 Old 10-14-2015, 06:33 PM
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I think people tend to concern themselves with shrinkage more than expansion because the moisture content of the wood is usually higher when you get it from the lumber yard than it is after the wood acclimates to its surroundings. Of course, that's not always the case.

I make my doors and drawers with a gap all the way around that's equal to the thickness of a popsicle stick (approx. 3/32" - or 1/10" -or- 2.5mm) I then use popsicle sticks as shims or props to hold the door or drawer centered in the opening while I fit hinges or drawer slides. I'm not saying that's gospel, but it works for me.
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