Weekly Tips JAN 07

January 30, 2007                                        
How to Make Strong and Permanent Glue Joints

1. Next to cutting wood, gluing is the next most common activity for the woodworker. Yet many projects that start out well may fail as a result of poor gluing techniques.
   
   Use Only the Best
   Firstly, with the array of wood glues out there under so many different names, consult with your local building supplier for what they offer in a premium wood glue. The cost of glue will not be a major factor in most projects so saving money on cheaper glue compounds is a poor choice. Popular choices include Titebond, Bulldog and Lepage all carry good products but there are others. Ask your supplier for the best they carry and “stick” with it! Also bear in mind that even the finest glue is not waterproof. There are water resistant glues and others rated as waterproof. Using a standard glue in outdoor projects will certainly fail in short order. The superior selection are waterproof epoxy based compounds that are premixed and then applied.
   
   Understand How Glue Works
   To create a good glue joint, it’s important to understand how glue actually works. Wood is actually a porous material made up of compressed fibres. The fibres run in patterns we call grains that were developed as the tree grew. Putting two pieces of wood together successfully will largely depend on what grain patterns interface. Typically, two pieces of parallel grains tend to glue up stronger than an end grain meeting a the long side of a grain. Predictably, joining two pieces of wood by their end grains is usually the weakest type of joint.
   
   Since wood is porous, the degree of penetration of the glue into the wood is usually proportional to the setting time of the glue. In other words, the longer the glue needs to set, the more opportunity it has to flow into the pores and create a strong bond. So the slower the glue sets, under similar conditions, the stronger it will be as opposed to a quick setting counterpart. Modern compounds however have in some cases made setting times less critical.
   
   
   Grain Orientation and Mechanical Methods
   Long grain to long grain joints are the strongest since the glue can grip the fibres along their length. End to end joints are more difficult since the glue can only grip the ends of the fibers. The glue will be more effective if the joint is under pressure, thus forcing the glue deeper into the wood pores and gripping more of the fibers. Screws and nails are good however biscuits dowels and splines can offer great glue joint strength without any visible signs at the joint.
   Consider dados when joining short or end grain situations. The dado joint increases the surface area of interaction and also employs more long grain surface to grip with. When working with the edge of plywood that involves long and short grain patterns in layers, treat the joint as an end grain material, and add dowels, splines or biscuits to the joint
   
   Glue Application
   Make sure that you spread a uniform layer of glue on all the surfaces to be mated. The more porous the wood, the more glue you need. Most joints fail as a result of uneven application or not enough glue to adequately fill the pores and grip the fibres. One good practice is to apply an even layer of glue to all parts and then apply a second coat making sure to fill the voids and sparse area. Then immediately apply your selected mechanical means of joining. When pressure is applied, you should see small beads of glue oozing from the joint. It’s best to wipe away excess glue with a damp cloth before the joint is dry, to minimize the amount of sanding and scraping that will be required.
   
   Humidity and Temperature
   Recall that the slower the glue sets in most cases, the more time it has to flow under pressure into the pores of the wood and grip the fibers. Make sure that glue is applied in relatively humid conditions, with a humidity of at least 40%. A dry shop will cause the glue to dry too quickly and compromise the strength of the joint. Dry air is also detrimental to wood in general and may cause some woods to crack even in storage. Most glues have a fairly wide temperature range of application. However make sure that glue is never applied when too cold and beware of hot illuminating lights that may concentrate direct heat onto the joint and dry it out to quickly.
   
   Pressure
   A general rule of thumb is that as long as the wood does not get deformed, the greater the pressure exerted to bond a joint, the stronger it will be. The pressure is what forces the glue into the pores of the wood. Adding scrap wood to clamps creates even pressure and will absorb any deformation caused by the pressure points of the clamps.
   
   
   The Key to a Successful Wood Joint
   A quality glue
   Correct Temperature and Humidity
   Adequate pressure and mechanical means
   Proper amount of glue applied
   Proper distribution of glue applied
   Adequate time to cure

January 23, 2007                                          
Simple Finishing Techniques for the Novice

Often the aspiring wood worker creates a work of art and then experiences disappointment at the end when it comes to finishing the project. Professional glass like finishes often require expensive materials and almost as many hours to finish as it took to make the item.

Finishing wood in simple terms involves:

• Sanding the surface
  Considering the preferred final color
  Application of stain and/or varnish

 Any flaws in the wood like cut marks, mill marks, gouges, dents etc. will be highlighted after a finish is applied. These flaws must be sanded out first. Your first go at sanding should involve a grit of about 100 to level the wood and remove imperfections. Next take a damp cloth over the wood and wipe the surface. This does two things:

It will remove excess sawdust
It will raise small wood fibers above the surface

(Always sand in the direction of the grain.)

The small wood fibers will raise up when you apply your finish leaving the surface bumpy. By raising them now you have an opportunity to sand them off. Now use a 150 grit sandpaper and re-sand the wood. This time you'll be sanding off the fibers and creating a finish that's almost ready for application of stain and/or varnish.

Now repeat the process one more time. Wipe the wood with a damp cloth. This time, you'll raise the tiniest of fibers. Use a 200 grit sandpaper and sand down the surface one last time.

Before you apply your stain, wipe the wood surface with a DRY cloth to remove excess sawdust. Don't use a wet cloth because you may still raise microscopic fibers making the surface less smooth. If you have an air compressor  blow the dust off with a nozzle attachment using moderate air pressure (50 psi).

Staining
If your surface is now smooth to the touch, you can apply your stain. The smoothness of the wood is more important than what you use to apply the stain. A brush, sponge pad or rag will all produce a good job, just make sure that you wipe off any excess so that the grain of the wood can stand out. Avoid non transparent stains that will compromise the look of the wood. These types of stains are best for outside applications like sheds and not for fine interior woodwork.

Always test your stain on some scrap wood to see what the final color and tone will appear like before you apply it to the actual project. When staining, start with smaller parts and areas. If you are staining a table start with the legs first and see how fast the stain dries and how it behaves. Do the table top last.

 Finishing
After the stain has thoroughly dried (religiously follow the manufacturer's timeframes), finishing the product will prevent water damage or discoloring of the wood from dirt or stains. For the novice, an oil based polyurethane compound work well with minimal skill required. Select a satin finish if possible. The sheen is not as dramatic as a gloss finish but will still hide minor imperfection. Gloss finishes while dramatic, can highlight imperfections profoundly.

You can thin the varnish 50% using a paint thinner for the first coat. This puts less actual varnish down on the wood but it will dry faster and smoother. After the first coat is dry use a 300 grit paper and sand the finish as smooth as possible. Wipe the dust off with a dry cloth and apply the second coat of varnish using a full strength mixture. if you use a brush, make smooth slow strokes to avoid bubbles. Sponge applicators are good too since they can be used and thrown away.

Work in a well ventilated area with plenty of light, preferable natural light. As you work, pay particular attention to flat surfaces such as table tops. Look at the surface from different angles. You'll see imperfections easier and will be able to smooth them out before the varnish dries. You can apply a third and forth thin coat after the second one dries if it needs it. However sand the varnish between coats except for the final one. Once it dries leave it as it is. Your project is finished!

January 16, 2007                                          
Buying the right Table Saw.....

For the serious Do-It-Yourselfer, a table saw will become the heart of their shop. In an earlier issue, we talked about the differences, pros and cons of the proliferation of compressors out on the market. Like compressors, table saw designs abound and prices that vary between $99 and up to $3000.

What is the right table saw for the craftsman, and why do saws vary so greatly in price?

A basic table saw at the low end of the spectrum will likely be an 8" version. The smaller 8" blade, as opposed to the more popular 10" version, will cut an inch shallower, since the radius of the blade will determine the depth of cut. The 10" blade has a radius of 5" as opposed to the 4" radius of the 8" blade.

A smaller blade also takes less power to spin, so it's likely that the motor will be correspondingly smaller too. This all saves cost. The chassis of the saw is usually made of high impact plastic and the top itself will be made from aluminum.

 The accessories, like the rip fence and miter guide will likely be a combination of aluminum and plastic. The motor typically attaches directly to the arbor to save parts, so the blades is spinning on the same axle as the drive motor. These usually start up with an annoying jolt and replacing the motor down the road is difficult and often not even worth it.

All the plastic parts and oversimplified construction may compromise the durability of the unit and not surprisingly, its accuracy. A standard 90 degree cut on a cheap saw may not be a precise right angle and accuracies become more apparent with other non standard cuts using the miter guide.

It's hard to create a mechanism that can rapidly adjust the rip fence while keeping the fence parallel to the blade. If you carefully measure the position of the rip fence you may see that it may be as much as 1/16" off from end to end.

One other thing you'll find over time is that the cheap table saw's controls, particularly the mechanism to angle the blade will tend to bind, and get harder and harder to adjust.

 It may sound that a cheap table saw has no redeeming qualities, but for the price it's amazing you can get a table saw at all!

 For a modest price, you get a table saw with: 

• Reasonable accuracy
• Compact that is easy to transport
• Good for occasional use
• Accepts the same blades as a professional saw
• Simple to lubricate and maintain

 Look for these features on a better table saw. These may cost $350 to $1,000:

• The chassis is metal and the top is cast iron. These superior materials will be more durable and enhance the long term accuracy of the saw
• Better saws have a sub chassis for the motor and the motor itself belt drives the saw arbor. This has several advantages. Firstly, raising or tilting the blade arbor is smoother and easier since you do not need to move the heavy motor. Secondly, you can adjust the speed of the blade by varying the pulley sizes on the motor or arbor for various jobs. A big job in hardwood is better done with a slower blade speed. Thirdly, motor replacement is much easier. Usually removal of the electrical connection and a few mount bolts facilitate motor replacement. A quality saw will last decades but may need periodic motor repair.
• Better saws have larger table tops. This makes cutting larger pieces as well as smaller parts easier and more accurate.
• Belt driven saws typically start up without that annoying jolt and if the arbor is on ball bearings, the blade spins smoothly and slows down gradually after power is turned off. Less friction means more power gets to the blade.
• Rip cuts as well as miter cuts will be more accurate
• Most higher priced table saws come with stands or are floor models
• Higher priced table saws typically have larger motors and higher blade rpms that make better cuts and handle larger and harder wood grades

 If you're on a tight budget, it's usually better to check out a better quality used table saw for the same money as a new one. Their longevity make them a better long term investment. Although I have a number of table saws, I purchased a good quality Rockwell beaver table saw from a retiring carpenter in 1970. Thirty five years later I have replaced the motor twice yet it works like a charm. That saw has seen a score of projects. At any given time, if you look in your local paper, you'll always find a handful of people for various reasons selling their table saw, and most have seen little use.

 That leaves the professional $3,000 variety left to consider. High ended saws may have some limitations for the home craftsman and in some cases are actually impossible to operate. As long as you can afford it and can justify the expense, a high ended saw will likely run on 220 volt power. Large motors need higher voltage to deliver the current needed for these tools. If you can set up 220 volt power, such a saw will be a joy to operate. However, in this price range, beware of saws with motors that run on three phase industrial power. Although these saws are state of the art, they won't run on household current. These were designed for industrial building with three phase power, usually at 550 volts, a far cry from the garage workshop!

January 9, 2007                                             
BETTER CUTS WITH VENEER PLYWOOD

Many of our projects call for veneered plywood. Here are some tips to make smoother cuts:

Avoid Cross Cutting – Plywood tends to chip the most when cut across its width (grain). Cutting along the length of the wood will help to reduce chipping.

Use the Right Blade – Special blades are manufactured for different cutting jobs. The number of teeth, width, angle, and rake of the blade all impact the cut. Choose a blade that best matches your specific cutting situation.

Circular Saw – cut with the “best face” down.

Table Saw – cut with the “best face” up.

Score the Cut First – Run the plywood through the saw removing only a minimal amount of wood. The next cut will leave a cleaner cut.

Masking Tape – Put masking tape over the cut line to help keep the fibers on the edge from pulling up.

Backing Panel – Attach a backing panel with strong double stick tape. The backer board will take the brunt of the damage.

Use a Router – A router fitted with a straight bit will cut a clean line. A pilot bit and straight edge will help provide a clean line.

Score with a Utility Knife – Score the cut line with a utility knife.

Buy a Panel Scoring Setup – Some saws can be fitted with a plywood panel scoring setup and are ideal if you have to cut a lot of plywood. The setup consists of a smaller blade that scores the surface of the plywood before it reaches the cutter.

January 5, 2007                                         
How to Square up a big project

Large cabinets are sometime a challenge to square up. Even harder, many of the shed projects we offer can really be a challenge to get the foundation or a wall perfectly square. A cottage or home is perhaps the biggest challenge to square up. Even a large metal square is not accurate enough. You can get a structure square by taking a tape measure and measuring alternate corners. The LONGER diagonal measurement represents the corners that are LESS THAN 90 degrees. The SHORTER diagonal measurement represents the corners that are GREATER THAN 90 degrees.

Adjust the longer corners so that they are closer together, by pushing each of them in and the shorter corners outward. Continue to make adjustments until the two diagonal distances are equal. We’ve checked squareness for building foundations that were 165 feet by 70 feet using this simple method.