Academy Notes and Tips
MAY/JUN
2003
Volume 46/Issue 3
IN
THIS ISSUE
Project
Articles
•
Wall-Hung Curio Cabinet
• Mobile Potting Table
• Pencil and Stamp Holder
DEPARTMENTS
•
Ask Smitty
• Owner’s Gallery
• Letters from Owners
Academy Notes
Furniture
Joinery
Service Pointers
MARK
V Speed Change Mechanism
Safety Tips
Safety Do's and Don'ts
What's
New
Shopsmith
and Lowe's Team Up
EDUCATION
• Find
A Shopsmith Woodworking Academy Near You
• National
Woodworking Academy in Dayton, OH
ONLINE
CATALOGS
• Online Accessory Catalog
• Request
Printed Accessory Catalog
• Online
Replacement Parts Catalog
MARK
V INFORMATION
• Find
A Shopsmith
MARK V Demo Near You
• Request
MARK V Information Package
LINKS
•
Links Worth Visiting
•
Free Woodworking
Tips
FEEDBACK
Contacting
Shopsmith
Copyright
2003.
Shopsmith, Inc.
All Rights Reserved
From
the Shopsmith Woodworking Academy
Furniture Joinery
Printer
friendly PDF copy of article
Techniques - Simple
But Critical
In many ways, the joints you choose to use for a project may be less critical
than how you make them. Just remember...the wood has to fit. A
poor-fitting joint that fulfills all three of the above requirements may
actually weaken your project and cause it to deteriorate much faster than
a well-made joint that only meets one or two of the criteria.
The techniques required in making a joint - layout, fitting and assembly - are not difficult, but they do require close attention-to-detail. Plus...they also require you to remember the three basic joinery rules.
Laying out a joint -- Always measure with just one tool. Also measure from just one reference point on any given tool. For example, never measure one component of a joint with a steel rule, and another component with a tape measure. Also, never butt the end of a tape measure up against the inside edge of a joint to take one measurement, then hang it over the edge of a board to take another. The slight variations you'll get as a result of doing these things can add up to big problems that will surely ruin your joint.
Keep a hard pencil handy to mark with - and sharpen it frequently. At your pencil tip wears down, your lines will get progressively broader, making it hard for you to be precise. If you must use a pencil, get a 6H pencil from an art supply or office supply store.
A better choice - if you can get used to using it - would be a scratch awl or artist's utility knife. Their metal points will remain sharp; the lines they scribe will always be the same exact width; they will tear through the wood grain as you outline your joints (eliminating unwanted splinters and feathers when you make your cuts); and you'll have no unsightly pencil marks to remove when you're finished cutting your joints.
 |
| Fig. 2 |
As you lay out he various joints, pay close attention to which way the wood grain runs on the mating components. Not only do you want to mate long grain to long grain as often as possible, you also want to be careful not to chop up the long grains into short grains (See Fig. 2), since short grains have limited strength.
Fitting a joint - When the time comes to make your cut, remember that every piece of wood has its own idiosyncrasies. Just the act of cutting will relieve tensions in the board, often causing it to actually change shape. As a rule, these changes are minute and almost undetectable - until you attempt to assemble your joint.
Custom-fit each board to the next. When it's practical, cut just a little wide of your mark, then shave your joint down bit-by-bit until you get the fit you're trying to achieve. How can you tell when you've got the right fit? When you can assemble a joint without a mallet and there's no slop - that's a good fit !
Some joints, of course, require a little slop. Dowel joints, as an example, are customarily drilled a little deeper than the length of the dowels to leave room for the glue. Large panels need room to expand and contract. Movable joints (such as sliding dovetails) may require as much as 1/16" to 1/8" of slop to slide freely. Just remember which way the wood moves and fit your joints accordingly.
Assembling a joint -- Always go through a dry run first - clamp up your mating components without glue - just to “prove” your fit. When you're satisfied, disassemble the joint and coat all the mating surfaces with glue. Always apply a little extra glue to the end grains - since they will absorb more glue than the long grains. And, even though these surfaces won't be as strong when glued-up as long grains, they'll still contribute to the overall strength of your joint.
Now, reassemble the joint and clamp it together. Remember that glue is much stronger when it cures under pressure. But, remember, too, that it's best not to tighten your clamps excessively, as to much pressure will cause your glue to squeeze out from between the mating boards, causing a weakened, “glue-starved” joint.
Often, it's a good idea to reinforce joints - particularly if you think they will be subjected to unusual stress or loads. Glue blocks are a great way to reinforce a joint where there is insufficient long grain to long grain contact. For example, if you back-up a corner rabbet joint with a glue block, the long grain of each board will contact the long grain of the glue block.
Nails and screws will act as tiny clamps to help hold your boards together. Nails are rarely used in fine joinery because they're unsightly and as the wood shrinks with age, the nails will loosen up and begin to come out. Screws, although often, just as unsightly, can be tightened from time-to-time, ensuring the continued strength of the joint.
