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Air-Drying Lumber

Air-Drying Lumber

It’s the low-cost, low-tech way to dry lumber. Here’s how to do it right.

By Dave Munkittrick

 

Want a truly cheap and easy way to dry lumber? Consider air drying. It’s the most economical method for removing water from wood, and when done properly, you’ll end up with perfect lumber.

Although air-drying is inexpensive and easy,be aware of these drawbacks:

It’s slow. Depending on the species and your climate, it can take from 2 to 12 months to bring 4/4 lumber from green to air-dry (12- to 20-percent moisture content, depending on your location).

Air-dry isn’t dry enough for indoor use. If you’re planning to use the lumber for outdoor projects, airdrying outdoors is fine. But if you plan to use the lumber for interior projects, you’ll have to re-stack it indoors and let it dry down to 6- to 8- percent moisture content.

Loss of material. When you airdry lumber, it’s not unusual to lose up to 10 percent or more to drying defects. Lumber defects occur when drying is too rapid, which leads to surface checks and end splits or when drying is too slow, which results in sticker stains and discoloration from fungal growth.Because air-drying is at the mercy of the weather, drying rates are difficult to control.

There’s not much you can do about the slowness or the final moisture content, but you can ensure that your lumber has the fewest possible drying defects. It’s all in how you stack the pile.Here’s how to do it right:

Put Your Pile in the Open

Locate the stack in an open area exposed to the prevailing winds. Avoid shady spots or low areas where moisture can collect on the ground.

Keep the area around the stack clean and free of vegetation. Debris from off-cuts or broken stickers and sawdust are breeding grounds for insects that can migrate to your stack. Control vegetation around an outdoor pile by laying down landscape cloth and covering it with gravel.

Click any image to view a larger version.

1. Box-piled lumber yields the most high-quality boards. The pile should have:

• Straight sides and ends

• Full-length boards on the outside of the pile

• Short boards staggered through the inside of the pile

• Offcuts used as spacers to bridge the gaps caused by short boards.


2. A slanted roof helps the pile shed water.You can do this in a number of ways; here we are using stickers on the top that vary in height to slant the roof to one end of the pile.

 

Prepare a Good Foundation

For outdoor drying, the foundation should be at least 18-in. high. We used 12-in. cement blocks and 4x6 landscape timbers to keep the bottom of the pile up off the moist ground and to encourage airflow through the bottom of the stack. Level the cement blocks to create a flat foundation.A dip in the foundation will telegraph through your whole stack resulting in less-than-flat boards. Place the timbers on 16-in. centers.

 

Prepare the Boards for Stacking

First, trim the ends of the boards so they are a uniform length. Be especially careful to remove any existing checks, because they’ll only increase during the drying process.

Then, “butter” the ends with a commercial end-sealer (see Sources, page 98). The money you spend on end-sealer will be more than paid back in better quality lumber. Make sure the coating is thick enough to indent with your fingernail.

You may find some variance in the thickness of your green stock. Sort your wood so that all the boards in a layer are within 1/16-in. of the same thickness.

 

Use Good-Quality Stickers

Stickers create gaps between the layers of wood. These gaps allow air to flow freely through the stack. Make your stickers from dried wood.They should be straight-grained and strong, so they can be used over and over again. Standard stickers should be surfaced to a uniform 3/4 in. x 3/4 in.Use 2- to 3-in.-wide stickers at the ends of the stack. The extra width helps slow the rapid loss of moisture at the ends of the boards and makes the stack more stable. Stickers should be slightly longer than the overall width of the stack. It is essential that each sticker be place directly in line with the one below. This creates a vertical column that transfers all the weight of the stack to the foundation.

 

Box-Pile the Stack

“Box-piling” is the best way to build your drying stack (Photo 1). In box-piling, full-length boards are used on the outside edges, and shorter boards are placed in the interior of the stack.Fill the voids at the ends of the pile with offcuts from trimming.

 

Put a Lid on It

If your stack is outside, it needs a roof to keep out damaging direct sunlight and rain. You don’t need anything fancy, although it’s good to have a slight slope in the roof for water run-off (Photo 2.) We used chipboard covered with tarpaper. It’s best if the roof overhangs the pile by 6 in.or more.

 

Weight the Stack

Weight (rocks, cement blocks, sandbags) will lock the boards in place, helping to prevent warp and twist as they dry. Plus, it keeps the roof from blowing away.

 

Control the Wind

To help minimize the effects of the weather, it’s best to have a tarp that can be dropped down the sides of the pile. This offers protection on hot windy days when the drying rate can be too rapid. This is important with hard-to-dry, check-prone woods like oak and hickory, especially when the green wood is above 30 percent moisture content.

After you’ve done all you can to protect the quality of your air-dried lumber, it’s up to nature.

 

 

 

This story originally appeared in American Woodworker June 2002, issue #94

June 2002, issue #94

Purchase this back issue.

 

 

How to Make Small Carving Tools

How to Make Small Carving Tools

By Mike Burton


I learned to make small carving tools out of necessity. I do intricate, detailed carvings, and the selection of small carving tools in catalogs is painfully limited. Solution? I started making my own. Not only can I make unusual sizes and shapes, but the handles are shaped to fit my hands. Plus, these tools are very inexpensive. Give them a try—there’s nothing like the feeling of using a tool that you have made yourself.

 

Supplies and Equipment

The raw material of these carving tools is drill rod, a tool steel available in various diameters. You can buy it from local machine shops or industrial suppliers for about $2.50 for an 18-in. length.

You’ll also need a metalworking vise, but it doesn’t have to be fancy. Be sure it has a flat “anvil” area for flattening the rod. My vise cost $15.

For heating the rod, use a MAPP gas torch ($35 at home centers). This is just like a propane torch except it’s designed for MAPP gas, which burns hotter than propane. You can’t use MAPP gas in a common propane torch.

A selection of files, small grinding stones and a small diamond hone will be needed for shaping the tools.

 

Working Safely

The flame from a MAPP torch is even more dangerous than the flame from a propane torch, so follow these safe work habits.

■ Prepare a safe work area. Remove sawdust, rags, finishes, wood scraps and any other flammables from your work area.

■ Keep the lights down low. This makes it easier to see the flame, and easier to judge the color of the heated rod.

■ Avoid tip-overs. The torch is top-heavy, and easy to tip over. I found an old, widemouth coffee pot that the cylinder of my torch fits into. When I’m not using it, the torch rests steady in the pot. You can rig up something similar.

■ Wear safety glasses. Tiny pieces of hot steel and scale can be dislodged at just about any stage in this project. Always wear your glasses.

■ Manage the heat. Whenever possible, work on long (18-in. or so) pieces of rod. Cut the finished tool off the end. If you need to heat a short piece, grip it with locking pliers. Don’t try to use drill rod thicker than 3/16 in.; MAPP gas won’t be able to get it hot enough.

 

The Basic V-Tool

The simplest small tools are filed directly into the drill rod, without any forging. This small V-tool is a good example.

Click on any image to view a larger version.


1. Form a v-shape with a triangular file on the end of an 18-in. piece of 5/32-in. drill rod. Bending the tip of the rod will give you room to work.


3. Form the cutting edge with a file and diamond hone, then straighten the shank. If this is the only tool you’re making, proceed to heat-treating (Photos 10 and 11) and attaching a handle (Photo 12).

2. Refine the inside with a diamond hone ($10). You may need to file down the plastic sides of the hone so it will fit in the tiny V.

 

Gouges, Chisels, and Skews

Very small gouges, chisels and skews can be filed directly from drill rod, just like the V-tool, using a small rat-tail or flat file. Refine the inside with a rolled-up piece of 320- to 600-grit sandpaper or a diamond hone. Larger tools need to be forged, as shown below.


4. Flatten the tip of the drill rod for larger tools. Heat the tip to a bright red glow with a MAPP torch, quickly place it on the anvil section of the vise, and hammer it flat.

5. For wider tips, first thicken the end of the drill rod by heating it to bright red and pounding the end to “upset” (compress) it. You can make the rod half-again thicker this way. After upsetting, heat the tip again and flatten it.


6. Make a crease to further widen the tip by hammering it against the edge of the vise. For more width, make several creases in a fan pattern. Heat the rod again, and hammer out the creases.

7. Use a swage to hammer the heated rod into a gouge shape. The swage is made from a length of 3/16-in. drill rod and a large bolt. The rod fits on a groove filed into the head of the bolt with a 1/4-in. rat-tail file. Sandwich the red-hot tool blank between the rod and the groove; then hammer.


8. Use a socket as an anvil to open up or form gouge shapes. Different socket sizes can be used for gouges of different shapes. This is also a good method for making curved detailing knives.

9. Grind the inside to refine the shape of a gouge using a cone-shaped grinding wheel in an electric drill or rotary tool. Roughly form the bevel, but don’t sharpen yet. The tool must first be heat-treated.


10. Slow cooling on an electric burner (annealing) will reduce stresses built up in the metal during forging. Heat the first 1/2 in. of the tool tip bright red, keep it red for 30 seconds, then place between the coils of a burner set on high. Every 10 minutes, lower the heat until the tool is cool.


12. Attach the handle last Heat the handle end of the tool and hammer the last 1/2 inch or so square to prevent twisting. Drill a hole in the handle, add a bit of carpenter’s glue and pound the handle onto the tool. For bent tools, hold the shank with locking pliers and pound on the pliers. Give the bevel a final grind, sharpen, and you’re ready to carve.

11. Tempering produces a hard, durable edge. Heat the tool tip to a bright glow for 30 seconds, then plunge into cold water. Polish the end of the tool to a mirror shine with fine sandpaper or emory cloth. Heat the tool slowly, keeping the flame about an inch below the cutting edge. When the edge turns a medium straw color, plunge it into cold water. (You may want to practice this!)




This story originally appeared in American Woodworker April 1999, issue #72.

April 1999, issue #72

Purchase this back issue.

 

 

How to Build a Torsion Box

How to Build a Torsion Box

It’s amazingly strong, light. . . and cheap!

By Alan Schaffter


Torsion Boxes–the Real Story

“How can something made from such thin wood be so stiff?” That’s what everybody asks when they first meet a torsion box. The engineering principles behind a torsion box are pretty simple; even so, there’s a lot of misleading information about torsion boxes, particularly on the Internet. Without getting too technical, here’s what you should know:

• A torsion box works like an I-beam (see right). It’s almost as strong as it would be if it were made from solid material–but it’s much lighter and less expensive.

• The thicker the torsion box, the stronger it will be–by a lot! If you increase a torsion box’s thickness by 25%, for example, it will be 100% stronger. If you doubled the thickness, it would be eight times stronger. Strength increases by the thickness cubed.

• The stiffness of the skins isn’t that important. A thick material, such as 1" plywood, doesn’t necessarily make a stiffer box than using thin material, such as 1/4" plywood. Thickness does matter in another way, though: thin material will deflect more easily where it’s unsupported, in the spaces between the web pieces. If you’ll be pounding on a torsion box, clamping things to it, or setting heavy objects with narrow feet on it, a thick skin is better than a thin skin. Or you could space the web pieces closer together.

• The thickness of the web pieces isn’t all that important, either. They can be relatively thin and lightweight, as long as they resist stretching and compression. For an MDF box, such as the one in this article, I usually space the web pieces 6” to 8” apart. The web pieces must be well-glued to the skins to prevent the skins from buckling, though. That means that the web material shouldn’t be too thin–it must be thick enough to have a sufficiently wide glue surface. You don’t need to use a special glue to assemble a torsion box–a PVA (yellow) glue works fine. And to clear up two misconceptions on the Internet: the webs don’t have to look like miniature I-beams, nor do you have to cut dados in the skins to receive the webs. Torsion boxes don't need to be that complicated!

Click any image to view a larger version.


Strong, but light

This huge torsion box is 8 ft. long, but it easily holds 300 lbs. of bricks and deflects less than 1/2". It weighs only 30 lbs., and is made from inexpensive 3/16" hardboard.



How an I-beam works

When you press down on a solid beam, you actually compress its top section and stretch its bottom section. These compression and tension forces are neutral at the beam’s center. In an I-beam, most of the center is removed, to save material and weight, but the forces still act in the same way.




A torsion box is a remarkable piece of engineering. It’s stable, light and uses a minimum amount of material, yet it’s extremely strong. The idea has been around for years, and you probably have one in your house: hollow-core doors are torsion boxes.

Making a torsion box doesn’t require any specialized equipment or skills–a guy with a small shop and a decent tablesaw can easily handle the job.

When I needed a flat, solid, durable and inexpensive top for an assembly table, I planned on making it as a torsion box. I researched the subject and found a lot of conflicting information. I also talked to some experts–and learned a lot.

In this article, I’ll show you how I built that assembly table top, but you can use this method to build a torsion box of any size or composition. If you stretch your imagination a bit, you can find many ways to use torsion boxes in furniture making: they can be desk or dining table tops, pedestal ends, shelves and, of course, doors.

 

Materials

A basic torsion box is composed of two types of parts: skins (the top and bottom) and webs (which form an internal grid, and include the sides of the box). Skins are usually made from an engineered material, such as plywood, MDF or hardboard. The webs and sides may be made from engineered material or solid wood. The web pieces do not need to interlock, as mine do, but it is quicker and easier to make the grid that way. Plus, the box will be stronger.

I used 1/2" MDF for all three parts. Though heavier than plywood, MDF has a more consistent and uniform structure. It is flat and stays flat, if properly stored. It has no internal stresses, resists compression and tension along the surface, machines easily, holds glue relatively well, and is relatively inexpensive. Using the same material for all the parts minimizes the amount of sheetstock you have to buy, and gives you more flexibility in cutting it up.

MDF that’s 3/4" thick would work, too, but there’s no significant advantage to it (see Torsion Boxes–The Real Story, above). Material that’s 1/2" thick strikes just the right balance, I think–it’s thick enough so you can safely nail into its edges, but thin enough to make a large table that's light enough to move.

 

Cut the web pieces

1. You will need only two sheets of 1/2" MDF to make the skins (A), web pieces (B and C) and sides (D and E). Break down the sheets into manageable pieces (Fig. E), then cut all the parts to exact dimension (see Cutting List, below). Rip the web, sides and leg socket reinforcing parts (F) at the same time to ensure they’re exactly the same width.

2. Set up your tablesaw to cut halflap joints in all the web pieces (Photo 1). First, adjust the width of a dado set to just a little bit over 1/2", or whatever it takes so the parts will easily slip by each other. Make an indexing jig to space the notches (Photo 2 and Fig. B). The jig is just a fence for your miter gauge with a small notch cut into it, plus a pin to fit the notch. Cut the notch after you’ve adjusted the width of the dado set. Set the distance between the indexing pin and the blade (for this web, it’s 7-1/4"). Raise the blade to cut a notch 1/32" deeper than half of the pieces’ width (for these 2" wide pieces, make the notches 1-1/32" deep). You don’t want the notches bottoming out when the web is assembled.

3. Cut the half-lap joints (Photo 3). Make the first cut with one end against the alignment pin. Slip the first notch over the pin and cut the next one. Repeat the process until all notches are cut in all web pieces. The distance between the last notch and the end of the web piece may be slightly different than the spacing between the other notches, but this is not a problem. Mark an "X" on all pieces at the end you started cutting from. Place all the "X" ends in the same direction when you assemble the web.

 

Build a construction platform

4. To make a torsion box that’s flat, you must build it on a flat surface. The best strategy is to make a temporary construction platform that you can adjust to become absolutely flat (Photo 4). All you’ll need is a pair of sawhorses and some straight and knot-free 2x4s (Fig. C). Joint one edge of all the 2x4s and run them through the planer so they’re all the same width. Place the sawhorses approximately 3' apart. Secure them to the floor with screws, nails, hot melt glue–whatever–so they won’t move. Add bracing, if necessary, to make them stable and rigid.

5. Place the long 2x4s on the sawhorses, then use hot-melt glue to attach the short 2x4s on top. Make a pair of winding sticks by jointing and ripping two thin boards that are 2" to 3" wide by 4 ft. long. Paint one board white and the other black. Place the winding sticks on the first and last supports. Sight across the winding sticks (a white backdrop helps) and insert shims under the long supports until the top edges of the winding sticks are parallel. Without disturbing the platform, securely attach the long 2x4s to the horses with hot-melt glue.

6. Place both of the skins (A) on the platform–this will give you a large, flat area to glue up the web and sides. Cover the topmost skin with thin poly sheeting to protect it from glue drips. Stretch the sheeting tight and anchor it with tape or thumbtacks.

 

Assemble the web and sides

7. Join one short and one long side (D and E) with glue and brads (Photo 5). Align and clamp these two sides to the edges of the skins. Place the long webs on the skins with the notches facing up. Slip one or two short webs in place to prevent the long webs from falling over.

8. Glue the web, starting from one end (Photo 6). Make sure the tops of both pieces are flush at each joint. Continue working towards the opposite end; apply glue and add one short web at a time. Place weights on the web as you complete each row.

9. Once all the webs have been glued, slide the grid away from the sides. Apply glue to the ends of the webs and position the grid back against the sides. Shoot a few brads through the sides and into the ends of the webs. Attach the remaining two sides with glue and brads. Remove any glue from the top of the webs, check that the grid is square, and let it dry.

 

Build leg sockets

10. This is an optional step. There are many ways to attach legs to a torsion box top–I chose to house them in sockets built right into the top. Begin building the sockets by adding reinforcing pieces (F) to the web’s sides (Photo 7).

11. When the glue is dry, temporarily place a leg in the socket and glue and clamp the remaining reinforcing pieces (Photo 8). Remove the leg before the glue dries.

 

Add the skins

12. Draw layout lines on the bottom skin for attaching it to the grid with brads (Photo 9). First, remove the grid and both skins from the platform. Replace the skin with plastic on it and put the grid on top. On the grid’s sides, mark the centerlines of all the web and reinforcing pieces. Mark the centerlines of each leg socket on the sides as well (you don’t want to shoot brads here). Place the remaining skin onto the grid and align two adjacent edges of the skin with the sides of the grid. Transfer your marks from the sides onto this skin, then use a straightedge or large square to connect the marks. This skin will be the bottom of the torsion box.

13. Glue the skin to the grid (Photo 10). To begin, remove the skin and place masking tape inside the leg sockets, to prevent glue from sticking here. Apply a liberal amount of glue to the edges of all sides, webs and reinforcing pieces. Work quickly and don’t be concerned about drips or using too much glue. Place the bottom skin on the grid and align the same sides you used when laying out the nailing lines. Shoot 1-1/2" long brads, spaced every 3", along the layout lines and along the sides (Photo 11). Place weights on the skin to keep it flat.

14. Drill and rout the skin to open up the leg sockets (Photo 12). The top I’m making also required additional pieces (G) to accommodate bolts that secure a set of leg braces. To install these anchor pads, turn over the top and glue them to the bottom skin. After the glue is dry, drill holes through the skin and pads and install T-nuts in the pads.

15. Remove the plastic from the top skin and mark it using the same procedure as you followed for the bottom skin. Glue the skin to the grid. Use a router and flush-trim bit to make both skins flush to the sides all around.

 

Add the facing and laminate

16. The torsion box is basically complete at this point, but I added hardwood faces (H and J) to the sides and plastic laminate (K) to the top. You can butt the faces together, miter them, or make box joints, as I did. I attached the facing to the torsion box with glue and brad nails (Photo 13) and trimmed it flush to the top.

17. Glue on the plastic laminate (Photo 14). If you want to avoid working with laminate, you could make the top skin from 1/2" MDF with one melamine face. It’s not quite as durable as laminate, but better than plain MDF.

18. Sand and finish the facing and the bottom skin.

 

Add the legs

19. The legs that I designed for this table are removable. They’re fastened to the top with bolts that pass through the box’s faces and reinforcing blocks. The bolts thread into T-nuts on the back side of the leg. Make a drilling jig (Fig. D) to position the bolt holes and to ensure that the holes are perpendicular to the legs. The jig has two holes, one for each side of the leg. Before drilling, mark the holes’ locations. Counterbore the holes so the bolts’ heads won’t protrude. Then drill the holes for the bolts, going into the legs (Photo 15). Finish drilling the holes through the legs at the drill press.



Cutting List



Fig. A: Exploded View



Fig. B: Web Notch Layout



Fig. C: Gluing Platform



Fig. D: Drill Guide



Fig. E: Plywood Cutting Diagram

1. Inside this torsion box there’s a grid of interlocking web pieces. Adjust the width of your dado set to make these pieces easy to fit together.


2. Make an indexing jig to space the web piece’s notches. Adjust the distance from the jig’s pin to the dado set, then fasten the jig to your miter gauge.


3. Cut equally spaced notches on the web pieces. After cutting each notch, pick up the piece and reposition it on the indexing pin.


4. Make a dead-flat assembly platform to build the torsion box. Use a pair of winding sticks to check for twist. If the top edges of the sticks are parallel, you’re good to go.


5. Place the top skin of the torsion box on the platform and cover it with plastic, which prevents glue from sticking to the skin. Assemble the box’s frame with a brad nailer.


6. Construct the grid by gluing one row at a time. Place weights on the completed sections to ensure the grid stays flat as the glue dries.


7. This torsion box has builtin sockets at the corners for removable legs (see Adjustable Height Assembly Table, page 48). Reinforce the corners with additional pieces of hardwood.


8. Temporarily set a leg in each corner. Fit additional reinforcing pieces around the leg and glue them in place. Remove the leg before the glue hardens.


9. Place the bottom skin of the torsion box on the grid. Mark the centerlines of the web pieces inside the box to guide your nailing in the next step.


10. Apply a liberal amount of glue to the entire grid, the frame and the leg reinforcing blocks. Work quickly so the glue does not harden before you install the skin.


11. Place the skin on the grid, align its edges and attach it with brad nails. Using a router and flush-trim bit, trim the skin so that it's even with the sides.


12. Open the leg sockets. Drill an access hole, then use a router with a flush-trim bit to define the edges. Square the corners with a chisel. Turn the assembly over and glue and fasten the top skin.


13. Fasten hardwood faces on all four sides of the box. Use a block to align the top edge of each face with the skin. Trim the faces flush with the bottom skin using a router and a flush-trim bit.


14. Apply plastic laminate to the top skin. This makes an ideal working surface– laminate is smooth, resists scratches and is more durable than melamine. You can pop off dried glue from it with ease.


15. Drill holes through the faces and reinforcing blocks for bolts that will fasten the legs to the top. The bolts thread into T-nuts in the legs.




This story originally appeared in American Woodworker December/January 2010, issue #145.

December/January 2010, issue #145

Purchase this back issue.