Cherry Tool Box Riser Question.

[Andre]

I'd like to build a riser for my Kennedy roll around between the base and top chest, and have 3 smaller drawers. I want to make it from cherry but the chest is in the barn. The barn gets from -10 - 110 degrees F and between 30-90 percent humidity in extreme years and I know the cherry will expand and contract. How much clearance will I need between the drawers and outer frame/box? I want to make it as tight as possible but still be able to open the drawers in the humid hot summers.
Thanks!

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[f350ca]

Build it when its hot and humid and it should loosen up in the winter. Cherry is a beautiful cabinet wood but wouldn't be my first choice for a tool box, too soft. The only dimension you should need to worry about is the sides of the drawers expanding vertically, and binding at the top. Width wise the frame of the chest should expand and contract the same as the drawers, which is very little down the grain.
On cherry kitchen cabinets I leave about 1/16 around the doors and drawer faces and they never seam to bind.

Greg

 

[mws]

What a timely question. I just received my latest copy of Fine Woodworking and they have a detailed article on wood movement in the August 2014 issue.

So, stealing a little info from that article, along with my own experience, here's some info to get you in the ballpark.

BTW, Greg, that's a beautiful cabinet.

Some basics: Wood expands and contracts mainly at right angles to it's grain. Dimensional changes along the grain are all but ignored but my general rule of thumb is 10% of the cross grain rate. I suspect you knew that already.

Cherry is listed as having a cross grain expansion rate of 3.7% for quarter-sawn and 7.1% for flat-sawn. You can generally expect there to be a 2:1 difference between flat and quarter-sawn wood for any species. This specification is for green wood to bone dry, which is about 30% to 0 moisture content. Average wood, stored indoors will run 6-12% from winter to summer in my area, New Hampshire.

Do the math: Accounting for a 6% change in moisture, using 7.1% as the maximum change over 30% that works out to be (6*7.1)/30 = 1.42% Using a 6" high drawer front, a 1.4% change would be 0.084". I would guess allowing 0.050" at top and bottom would be very adequate.

From your post it would seem you need to accommodate a greater range of moisture. I doubt the MC of your wood, even in the most humid of shops, would ever return to it's "green" level of 30%, but I've never been able to justify the cost of a good Moisture Content Meter in my wood working, so I wouldn't know.


I've also found that a good penetrating wood finish, like Tung or Danish Oil, helps slow wood's absorption of moisture. I cannot say the same for surface finishes as I rarely use them. Judging by the finish separating from the wood, and generally loosening up, on my store-bought utility items I'd say such such finishes do little at all in this regard. Not that you'll be using Polyurethane on such beautiful pieces of wood, but I've seen people whack up clear maple and walnut for kindling. If I can turn a pen or a screw plug from a piece of fine hardwood I save it.

Sorry for the long rant, I hope that helps. We'll eagerly await some progress pictures.

Best Regards,
Mark

 

[JohnG]

Cherry would be an excellent choice for a piece exposed to moisture and temperature extremes like you describe as it is both stable and durable when exposed to high moisture. It was preferred at one time for window sash in railroad coaches which might travel back and forth across weather zones repeatedly.

The easiest way to minimize binding problems in the drawers is to mount them on extension slides. That way only the front of the drawer has to be tightly fit into its opening. The drawer box can be made 1/4"-1/2" undersized height-wise and flush with the front face at the bottom edge. Mount the slides low so that all movement occurs up, and you only need to shave the top edges of the fronts next August to a hairline gap.

In the millwork industry, we figured 3/16"- 1/4" per foot cross grain wood movement seasonally for solid wood exterior door components. Mark's calculation is right in line with that.

Forest Products lab did a study of moisture vapor transmission rates for different wood finishes. It used to be on their website. Penetrating finishes do little to slow MVT. Cured resins like epoxy or polyurethane do best with MVT also being a function of film thickness. I prefer polyurethane as it's just too much work to build film thickness with epoxy.


Use a moisture resistant glue for any edge gluing. A pre-catalyzed PVA like Titebond 3 is good. Urea formaldehyde also works well if you have a way to heat the glue line to cure it.

Greg, very nice grain matching in that cabinet.