Gottshall Block Follow Up

At last weekend’s Woodworking in America conference, I talked with several readers about projects I’ve made for the magazine. As expected, I was asked about my workbench and furniture projects, but  I was surprised about how many people sought me out to discuss the Gottshall Block. It turns out this project inspired many woodworkers, raised some controversy and even inspired a troublemaker to try to stir things up. Before we get the the controversy, let’s give the troublemaker his moment in the spotlight.

Reader Steve Taylor decided to accept the challenge of making the block, except for the part about using hand tools. His example, shown above, was made entirely with power tools. He and I talked at the show and I got to see his block. A big part of this challenge is marking the layout, and getting all the cuts in all the right places. That part went pretty well, but as you can see, the finished surfaces aren’t exactly what you would call refined. I found myself wishing I had a chisel to pare off the tool marks. You can read about Steve’s experience in this post on his blog.

Reader Corey Megal also stopped me in the hall to talk about his attempt at making the Gottshall block. Corey’s local woodworking guild took on the challenge and held a contest to see who could make the best example, and here is where the controversy arose. It revolved around the location of the center point for the 1″ radius on one corner of the block. In the original post on laying out the block, I mentioned that there was a trick to the location of this point, but I didn’t offer up a solution. The photo of this step, however does leave a pretty good hint. One might assume that this point is 1″ in from the long edge and 1″ down from the end. But if you do that, the arc doesn’t end neatly at the corner of the notch. It almost works, but it shortens the straight line on the end of the notch. Some of Corey’s guild buddies assumed there was something wrong with the drawing, or the measurements and made their blocks too wide by 1/16″. There goes their “A” in shop class.

The beauty of this thing is that Gottshall was one of those teachers who knew how to present a problem that forces you to think in a different way. I can easily imagine him saying “when you assume, Mr. Lang, you make an . . .” All the information is there in the drawing, and the conditions aren’t unreasonable; make an arc with a 1″ radius that ends tangent to both the long edge of the block, and the outer corner of the notch. So the center point of the arc is indeed on a line parallel to the long edge of the block. But as you can see in the photo above, it doesn’t line up with any edge or corner of the notch and it’s just short of being a quarter circle. Nobody ever said it was supposed to be a quarter circle. If you assumed that, and it caused troubles, well, you know what happens when you assume.

For the arc to end pleasantly at the corner of the notch, the center point must be 1″ away from the corner. Draw an arc with a one inch radius from the corner of the notch at the end of the board. (This point is 15/16″ away from the upper right corner of the block, if you’ve been doing the math.)

Where that notch intersects the line parallel to the edge is the center of the arc that rounds the corner. The image below shows this step-by-step and you can click on the image to see a larger version.

–Robert W. Lang

3 thoughts on “Gottshall Block Follow Up

  1. tman02

    I agree that if you do the math you see that the radius does not form a quarter circle. And if you don’t you WOULD think you had to make the blank 1/16″ wider than it is suppose to be.

    But then I guess I have an advantage over a lot of woodworkers having been a draftsman for over 40 years.

  2. Moontoad

    I don’t believe that the condition that the arc be “tangent to both the long edge of the block, and the outer corner of the notch” is met by the solution shown, as the arc at the corner of the notch is not exactly perpendicular to the radius of the arc. Close enough that the eye might not see it, perhaps, but I can understand it generating a discussion among a group of woodworking perfectionists.