Friday, May 26, 2017

warping lid...

A reader asked about a lovely box he had made of white oak sides and solid zebrawood top. About a week after cutting the lid from the body of the box, the lid warped severely. Here's the story in his own words.
When I retired, in 2015, I wanted to make wooden items. Your box books got me started. By now I have made a dozen and been guided by your hand and refer to the books all the time. If you have the time I would appreciate your advice on a problem I have never had before.

8 days after completing this box the lid started to bow. 8 days!! The first week dead straight. I have tried cauls holding it bent the other way for 5 days, still bowed almost 1/8” in the middle. I can get it straight after using a heat gun, but not while the heat gun is heating it up. It straightens as the wood cools off to room temperature, but after an hour it bows again?! 175F degree oven for a few hours which does the same thing as the heat gun, as it cools, it’s straight, but a few hours later, it’s bowed again?! Sprayed water on the concave side to increase swelling put on the cauls, let it dry overnight, no effect. I have 12 days to correct this problem before presentation to a HS grad, my granddaughter. The lid and box are white oak, and the grain pattern flows around the box, ( so I don’t really want to redo the lid) and that oak was dead flat and straight AND dry when I cut it. It had been in the shop two years. The lid insert is book matched Zebrawood panels 3/8” thick I cut from a bigger piece. I believe it was dry too. But I never put a meter on it. I believe the problem is in the Zwood. It was a very tight fit inserting the Zwood into the rabbeted top of the box, before I ran it through the tablesaw to separate the lid from the box. But why 8 days to show up!?
My questions in response where:
How is the lid panel held in place? Is it a floating tongue and groove panel or is it simply glued in place? If it is glued in place, the answer is easy. To my eye it seems immediately apparent that it’s a tight fit, and that the zebra wood panel has expanded, forcing the lid to bow.

It appears to be a lovely box, but for the problem you (he) had with it. Dealing with expansion and contraction of wood is a challenge. Both expansion and contraction offer challenges. Build without allowing for expansion and the problems do not take long to become apparent.
It turned out that my observation was right. He had glued the panel in place. A painful lesson learned. Wood as it expands and contracts can exert an amazing amount of force. It can push joints apart, or if glued in place, will likely bow. So how can he fix it in time for his granddaughter's graduation?

I have had some luck getting boxes to come apart after removing the metal parts and putting in the microwave. It sounds crazy, but I’ve put just a bit of water in the corners of the joints and heated for as long as 15 seconds at a time.

That can soften the glue (elmers or tightbond) to the point that things can be moved or even pried apart. But the top panel being glued in place will require a lot of steps in the microwave and there is the risk of irreparable damage.

It may just be better to bite the bullet and make a new lid. And the lessons learned, painful as they are, will not be forgotten. The reader suggested that I share this to help others avoid a simple mistake. Allow solid wood panels the opportunity to move. They will.

I learned my own lessons in this regard and what my reader experienced is not uncommon.

Make, and create.

Sunday, May 14, 2017

pallet wood for box making...

Readers are welcome to submit questions about box making and I'll try to help.

A reader from Washington State commented:
I'm just getting started making small boxes and practicing with Oak from old pallets. At 73 I'm a bit old to be starting this but I've found I really enjoy making boxes. I'd like to get good at this so I'm reading and watching everything I can and came across your site and purchased your books. Got my wood all milled down just shy of final dimension and I've been letting it sit and now I'm getting some bowing and twisting.

I was surprised old pallet wood would do this especially after it has been sitting in a metal shed on my ranch. Seems like the more you mill down your wood the more you release it and get the deformities. I'm using my Incra I-box jig and have done a number of plywood boxes with success and a couple of pine boxes successfully but this is the first time with Oak. I guess my choice is to mill it down some more and not let it sit or try to see how it comes out the way it's milled now.

Appreciate any help/insight.
Pallet wood can have some disadvantages. It’s free, but often not without costs. Pallets are often made of lesser quality woods and nailed together green, so stresses in the wood are constrained as long as it’s held tightly together and then are released when cut apart.

Wood in pallets also is cut thin and dries quickly, so it could suffer the same problems that can result from kiln drying at too fast a rate. That effect is called “case hardening,” in which the inside of the wood and tensions on the surface of the board are inconsistent. Jointing and planing can release tension in the wood in that case.

When wood is stickered and dried, either properly in a kiln or just stacked in the barn, it gets air circulation on all sides but is still free to move some as it dries. If using pallet wood, you might go for a more rustic look, and save the finer techniques for finer wood. I think that trying to do the joinery quickly before the wood changes can be a formula for disappointment. Warping wood is a powerful force that can distort the shape of a box or cause it to break apart. When it comes to wood, each piece is unique, and worthy of scientific examination.

I have no definitive answers. Have fun, and if you get a pallet wood box to hold together, send me a photo.

Make and create...

Thursday, May 11, 2017

safety blocking...

A reader of my book, Build 25 Beautiful Boxes read in my sidebar on router table safety that I suggest the use of safety blocking to make various router table operations safe.

He had not noticed any photos in the book to help him to understand what I had in mind. The first photo is from page 16 of that book. The idea is to completely cover the router bit in such a way that the work piece can enter the cut, but the fingers cannot. In both photos the router bit is buried under the safety blocking and inaccessible. The blocking must be clamped tightly in place.

The next photo is from page 85 and shows a climb feed cut. In this photo you can see how the blocking is built in layers to provide clearance for the router bit to rotate freely.

Another reader asked where she could take classes from me. My summer calendar is shown on my website here: DougStowe.com In addition, I often travel to teach for various woodworking clubs throughout the US.

Yet another reader asked about the Porter Cable 505 half-sheet sander that I've used in my books. Porter Cable half sheet sanders are no longer available new, but my reader found one for sale on eBay. There are others there for sale as well.

Make, and create.