Archive for ◊ September, 2017 ◊

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• Saturday, September 30th, 2017

wedged mortise and tenon

The usual directive is to flare the end grain mortise walls and wedge the tenons against those walls, as in the photo above. With the opposite configuration, which has the side grain mortise walls flared, there is reasonable concern that the wedges might exert pressure across the grain of the mortised board sufficient to split it.

However, there is another important way to consider this joint.

In the conventional configuration (photo above) with a well-fit joint, strength is created by the glue bond of the long grain-to-long grain interfaces, which are not wedged. In the long grain-to-end grain interfaces, which are deficient as glue surfaces, strength is created by the mechanical action of the wedges. Thus, all four interfaces contribute to the strength of the joint.

In the opposite configuration (as in the photo below), the wedges apply some “clamping” pressure for the long grain interfaces, but I would contend that is largely superfluous. At the same time, the long grain-to-end grain interfaces are mostly wasted as strength components.

Therefore, to maximize the strength of this type of joint, the conventional wedge configuration is better. In all cases, I think it is best to clamp across the joint and then insert the wedges.

Now, realistically, splitting is not likely in the opposite configuration with judicious wedging, especially if the joint is not too near the edge of the board. And the multiple mortise and tenon joint is probably more than strong enough in either configuration for its typical applications. Still, it is a labor intensive joint and one therefore tends to minimize the number of tenons, so it pays to get the most strength from each one.

The whole point here is to think about what is actually going on in the design of the joint, and make rational choices.

You can find step-by-step instruction on making this joint in my article, Making Multiple Through-Mortise-and-Tenon Joints, in the August 2008 issue (#170) of Popular Woodworking magazine. By the way, an important aspect of my method is to not use a fully housed tenon board as is often advised.

We should not be too definitive about these matters because each piece has different requirements for strength and appearance, and other factors inevitably influence both. Interestingly, in the same issue of PW, Bob Lang uses dual M&Ts to join shelves to the sides of a bookcase, using an approach very different from mine. Yet, I’d bet his bookcase is still going strong.

[Photo of the “opposite” configuration courtesy of Mark Ketelsen.]

Category: Techniques  | 2 Comments
Author:
• Saturday, September 30th, 2017

Supercut bandsaw blade

Readers of this blog know of my fondness for the bandsaw. More than almost any other tool in the shop, a fine quality bandsaw allows you to upgrade your range of designs and unlock the wonders of wood.

With that in mind, here is my favorite bandsaw blade – the one that is almost always on my 16″ Minimax: the Supercut Premium Gold 1/2″, 3 tpi. The band is .025″ and the alternate set, aggressive hook teeth produce a kerf of about .044″, or slightly less than 3/64″.

Here’s the big deal about this blade: the teeth are carbide impregnated, which keeps them sharp vastly longer than those of conventional carbon or silicon steel blades. I have used this blade for years, feeding it thousands of feet of everything from dense exotic species to knotty construction lumber, and it remains quite serviceably sharp. Only that it is no longer as crazy sharp as it used to be, has me now wanting to replace it at the very reasonable price of about $31 for 143″.

Now, a 1/2″ blade may not suit much of your work, but it’s just what I need for the gradual curves characteristic of my work. Its nominal minimum circle diameter is 3 5/8″. What’s more, this blade resaws fast and true all the way up to the 12″ capacity of my saw – no blade changing needed. Virtually every project I make involves these two processes.

The hook teeth with this amount of set should not be expected to produce a surface ready for gluing laminates or thick veneer, but with a well-tuned bandsaw, the surfaces do not require a lot of clean up. I’ll go to other options if I really need an excellent surface directly off the saw.

All of the manufacturing details are excellent, including the weld, and especially the outstanding sharpness. Supercut Premium Gold blades also come in 1/4″ 6 tpi hook and 3/8″ 4 tpi hook.

The blades are made by a family-owned company in northern Idaho, the kind of small business I like to support. Supercut also makes an extensive line of other bandsaw blades and accessories. They will provide personal attention to your order on the phone.

As usual here, this review is unsolicited and uncompensated. I just really want you to use excellent tools made by good companies so you can make great stuff!

Category: Product reviews  | 6 Comments
Author:
• Wednesday, September 13th, 2017

woodworking skills

How would you reply if someone asked you, “Are you a good woodworker?” I think most of us seriously involved in the craft eventually ask ourselves this question. So, what might comprise a test of fundamental furniture making skills?

Here is what I suggest as a basic skill set for making furniture and accessories. It obviously does not encompass all of woodworking, nor does it include specialized techniques. As such it does not include skills, some of which you will eventually want to add, such as carving, turning, wood bending techniques, resawing, veneering, and finishing. And, of course, everyone will be able to cite exceptions and omissions.

The “test” recognizes that good work can be accomplished with both hand tools and machines, but also that principles of hand tool woodworking form a solid basis for learning and understanding the craft.

1 Wood:

  • Assess several boards of wood regarding grain orientation, defects, seasoning, and fitness for various uses.
  • Demonstrate an in-depth understanding of a few favorite species.

2 Stock preparation:

  • Using only hand tools, foursquare a rough 4/4 board, say 6-8″ wide by 18-24″ long to 3/4″ thick. The product should be sized to a snug fit between standards in length and width (fit by shooting).
  • Smooth the surface to an excellent appearance without applied finish.
  • Do another board with the aid of machinery.

3 Joinery: Make the following joints, demonstrating knowledge and skill in the critical aspects of joint design, strength, and appearance. You can use hand tools and machines, as long as the method does not reduce the quality of the outcome.

  • Use edge-to-edge joints to make a three-board panel, 12-18″ wide and 24-30″ long.
  • Make a three-shouldered blind mortise-and-tenon post-and-rail joint.
  • Make a through-dovetail joint with at least four tails.
  • Make a frame mortise-and-tenon joint of your choice.

4 Additional skills:

  • The tools for the test will be provided in good working condition but the “instructor” will randomly throw in a tool that will require minor tune up, so you will have to know how to assess all of them.
  • Starting with the factory grind, sharpen a 2″ plane blade according to its application (e.g. in a smoothing plane), a 1/2″ bench chisel, and a card scraper.
  • Layout, cut, fair, and smooth a reversing curve in 8/4 stock, 18-30″ long.

5 Basic constructions: All of the above skills are academic if you cannot integrate them to produce the fundamental constructions of woodworking. Again, you can use hand tools and machines, as long as the method does not reduce the quality of the outcome.

  • Build a dovetailed box/carcase in solid wood ­– just the four sides will do.
  • Build a post and rail frame – a “table” with straight legs and no top will do.
  • Build a frame-and-panel door.

These are just raw basic constructions but the results must be neat, flat, true, and square. You must demonstrate the ability to control tolerances. Within reason, the size of the constructions is up to you but the precision will be scrutinized commensurate with the size. (Hint: smaller is not necessarily easier.)

A few more things:

  • The test is timed only if you make money from woodworking; otherwise, within reason, it’s not.
  • You have to be able to design what you want to build, or at least be able to follow plans.
  • You can do the test in your mind if you want, but don’t cheat!
  • You automatically fail if you don’t enjoy every bit of it.

You’ve arrived.

Category: Techniques  | 3 Comments