Lost Art Press

Sine Curve Tutorial

Posted on by fitz

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To develop the curves in the various brackets – here the support for the back fence on the lid of a desk – I followed the ancient practice of melding arcs of a circle along a straight line.

Sweet 5

Sweet

 

 

 

 

 

 

 

 

 

I begin by making a few concept sketches to get an intuitive feel for the curve I would like to see transition the horizontal lid surface to the vertical back fence. I’m going to go with the shape in the first drawing.

Sweet 2

Sweet 4

 

 

 

 

 

 

 

 

From the sketch, it reveals that the overall form suits that of a 1:2 rectangle. (An octave, by the way – but that’s another story). Next, I divide the horizontal length into four equal segments. The first of these segments defines the flat at the top of the curve. I then draw a baseline for the sine curve from this segment point to the lower right hand corner, then divide that baseline into three equal segments.

Sweet 1

Sweet 3

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

To find the focal point of the arcs – which will each be one-sixth of a circle’s circumference – I set the dividers to the length of the segment (which is the chord of the arc) and swing out intersections to locate the focal point of the arc. Next, without changing the span of the dividers (because the chord equals the radius for sixth sector arcs as you may remember from Mr. Hammersmacker’s seventh grade geometry class), I swing the arc from the focal point to each segment point. The transition between the two arcs is seamless – proven to be so because a line connecting the two focal points will pass through the arc’s transition point.

Sweet 16

— Jim Tolpin, byhandandeye.com (drawing by Andrea Love)

Where Chair Comfort Comes From

Posted on by Lost Art Press

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Many woodworkers avoid chairmaking for the joinery, the angles, the special tools required or the materials (green, rived stock?). And when it comes to designing a chair, even experienced woodworkers are hesitant to give it a shot because they are afraid they will produce a buttocks-torture device instead of a comfortable chair.

Producing a comfortable chair is the combination of many factors, but all of them are easily controllable. In my short 13 years as an amateur chairmaker and designer, here are some of the design details that I think are overlooked.

The Saddle
Many first-time chairmakers carve the seat so deep you could bake a Bundt cake in it. I’ve seen saddles that are 1” deep and so dramatically shaped that they would look at home on a Klingon battle cruiser.

A little saddling (3/8” or so) is nice and it makes the seat appear to flow. But you can get away with little or no saddling and make a perfectly comfortable chair.

The trick – in my experience – is to design the chair so the front edge of the seat doesn’t bite into the sitter’s thighs. You can do this several ways.

No. 1: Shorten the legs a bit so the sitter’s feet rest flat on the floor and their thighs are just slightly above the front edge of the seat. Many shorter people hate factory chairs because the front edge of the seat restricts the blood flow after a few minutes.

Just like with a table, it’s easy to make it too high. But making it a little lower than typical has zero downsides.

No. 2: Take a jack plane and round off the front edge of the seat. You can also do this with a spokeshave – hollowing out two areas for the thighs. This five-minute operation creates the illusion of a saddle and increases the comfort.

The Back Legs
The least comfortable chairs I’ve sat in had a seat that was parallel to the floor. It makes the sitter feel like she is being pitched forward.

I like to have the seat drop 1” (at least) from the front edge of the seat to the back edge. I achieve this by cutting the back legs shorter. Cutting the back legs also has the benefit of angling the back of the chair backward, increasing the comfort.

Don’t over-do it. After removing 1-1/2”, it will start to feel weird. A good way to experiment with this is to prop up the front legs on a 1”-thick scrap and sit in the chair.

The Angle & Height of the Back
The backrest doesn’t have to be bored at a reclining angle. You can bore the backrest at 90° and use the fact that the back legs are shorter to make the chair comfortable. However, I do like to recline the back a few degrees back (once you get into chairmaking you’ll find that all the angles are as easy as 90°).

What I have found to be quite critical is the height of the crest rail or backrest. In general, lower seems to be better. Once you put something above the shoulder blades, the lumbar seems to suffer.

You can design a chair that has a high backrest, but I think it’s best to also have something below as well for the lumbar (think Jennie Alexander’s chair).

About the Chair Above
Roy Underhill made the chair in the photo at the top of this entry. It’s a reproduction of a chair we both saw at Stratford-upon-Avon last summer. To the eye, it looks uncomfortable. The seat is flat. The arms and seat height are lower than a typical modern chair. And the area created by the arms seems like a tight fit (it is for large people).

But the chair is remarkably comfortable. And, if you watch the current season of “The Woodwright’s Shop,” you’ll see how it’s dirt simple to build.

— Christopher Schwarz

The Number of the Name is….

Posted on by fitz

sector for fractions While I mostly use the sector for doing design and layout work in my shop, I realized recently that it’s also a great tool for showing someone (especially your kids) an intuitive approach to understanding fractions. Here’s how I’d describe what’s going on in the drawing above:

Because I want to find out where a point four-sevenths of the width of a board would come to, I set the legs of the sector to touch each edge of the board to denominate (i.e. to name) the kind of divisions I’m looking for. Here, that would be seven – the denominator. Now I want to enumerate (i.e. give a number) to how many of those sevens I’m looking for – in this case the numerator is four. The job of the dividers is to grab this numerator above the denominator value on the legs of the sector in order to transfer the setting to the face of the board. For me (and my kid), this drawing offers a decent visualization of why the numerator goes over the denominator. You can learn more about the sector in excruciating detail in “By Hand and Eye;” and in a somewhat less excruciating matter in “By Hound and Eye.”

— Jim Tolpin, by handandeye.com

Forum Update 9/26

Posted on by meghanlostartpress

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Good morning! Another weekend over and another busy week is upon us. No matter how crazy life is, make sure to take some time to read the forum and see what your fellow woodworkers are up to. Remember, if you have a question about our products, procedures in our books or anything related to Lost Art Press, the fastest way to get an answer is our forum. Check it out here.

No. 7 Adjustment Issues
Kendall took apart his Lie-Nielsen No. 7. to sharpen the blade but now that he is putting it back together he cannot get the blade to adjust below the sole. He is looking for any help on what he may be doing wrong. Let’s see if we can prevent him from having to make a call into Lie-Nielsen. Help him here.

Handworks 2017
Does anyone who has attended Handworks have a recommendation for a place to stay? Steve is ready to get his plans together and is looking for input.

Spare Bedroom Workshop
Mark and his girlfriend have found a house that they love and want to buy but there is no garage or basement to use as a workshop. Mark is looking for feedback from anyone who has used a spare bedroom as a shop before. Did it work out? How was the noise? Was dust all over the house?

Crucible Dividers
Jason likes the pictures of the Crucible dividers but wants to get to the point and find out how they work. If you have a pair, let him know what you think.

Hot Hide Glue Gelling Quickly
Josh has had success with hot hide glue on small pieces but has had no success with it when trying to glue up a panel. Every time he finds he is unable to close the joint. He is wondering if anyone would be able to help with why this is occurring.

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Staked Chair
Travis has made a pair of staked chairs from “The Anarchist’s Design Book” and they turned out great. (Photo at top and to right.) The beveled edges are a great touch!

— MB

Collapsible Bookshelves

Posted on by meghanlostartpress
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A collapsible bookshelf modeled after a teak original.


This is an excerpt from “Campaign Furniture” by Christopher Schwarz.

Bookshelves that fold at or disassemble are common items among surviving pieces of campaign furniture. These ingenious units were generally pretty small. After all, it’s not as if you were traveling overseas with a Carnegie library, and books of the 19th century were usually compact items.

How small? A typical campaign shelf unit is 3′ wide, 2′ high and 8″ to 10″ deep. That’s not a lot of shelf space.

Many of these shelving units were designed to sit on top of another piece of furniture, such as a campaign chest or desktop. Or they were intended to hang on the wall, which was especially handy during a sea voyage.

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Screwed together. The metal uprights screw together with the shelves to produce a fairly sturdy set of shelves.


Common Types of Portable Shelves
The most common type of portable shelf isn’t one you’d expect to see in a book on woodworking because it’s mostly metal. These shelves are tubular metal uprights that screw together with two, or usually three, wooden shelves between.

These shelves look spindly but are robust enough for the job.

A less-common variant on these shelves replaces the metal with wooden uprights – usually turned spindles – that screw together with the wooden shelves to produce the finished piece.

Another type of shelving unit is a folding book rack. The simplest form of book rack has a at shelf with two “bookends” that fold flat while traveling. These simple racks are not exclusive to the campaign style; you’ll find variants during every furniture period where books were common.

The ends of the three boards are mitered and hinged. Sometimes the ends have handles so you can lift and move the loaded rack.

There are more complex mechanical book racks that also expand in length as well as having folding ends. These usually require some tricky hardware to make them function well, so I decided not to build one for this book.

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For hanging. These large folding shelves were designed to hang on the wall. Note that the barrels of the hinges on the uprights are equidistant from both the top and bottom of the case. This detail allows the unit to fold flat.

The third common type of collapsible shelving unit folds like an accordion. You usually remove a center shelf (or two), and the uprights fold in on themselves, turning your shelf unit into a flat pile of lumber. The first time you see it in action, it’s actually a little bewildering. But it is quite cool.

This type of shelf unit requires no special hardware – just a small pile of butt hinges. And there is almost no real joinery to speak of. So it’s an ideal project for the woodworker without access to a forge or a metal shop.

These accordion-style shelves came in several dierent sizes and configurations that were embellished or plain. Some versions were designed to hang on a wall; others sat on top of a chest or desk.

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The original. This is the original version of these shelves in teak. I altered the top profile slightly, but otherwise mine is quite similar. (Courtesy of Christopher Clarke Antiques)

The shelves I built for this book are based on a unit I admired in one of the Christopher Clarke Antiques catalogs. The original was made from teak; mine is mahogany. While the only joinery in the whole project is cutting two dados, you will become quite an expert at installing butt hinges. It takes 12 hinges to get the whole thing to work. And installing the hinges precisely makes the shelf unit sturdier and makes it collapse more smoothly.

— MB