100-year-old finish carpentry secrets: locking a miter joint with a ring
Here's a miter lock you may not have seen before: A hexagonal ring inset into a circular cutout with a central core housing the ring that holds the joint together.
Richard was working on one of our friend Brent Hull's historic preservation jobsites, and Brent showed him this detail on a flat casing profile from the 1920s. Removing the ring reveals that the outer cut is a circle, but the inner core (the donut hole) is hexagonal.
The proof is 100% in the pudding. After 100 years, the miter is still tight—even after being removed from the wall.
So many questions...
- What do you call it?
- How did they cut the circle?
- How did they shape the core into a hexagon?
- Were yesterday's carpenters smarter than today's carpenters?
- Did yesterday's carpenters put more care into their work?
Jonathan goes deep on his theory about how this was cut, formed, and fastened. A quick scroll of the comments reveals a lot of the answers to the above questions:
"When I was a teenager I worked with an old timer that had a machine for this purpose. There were several different size kerf drill bits for different widths of molding.
The mitered or squared molding would be clamped flat side down and the bit would come up from the bottom by pressing a foot pedal. Then the pieces would be moved to another part of the machine where another bit would chisel the hexagon. Sometimes the chiseled pieces would fall off, if not it was quick work to shave them off with a hand chisel.
There was another machine that would press the metal ring in but it was easier just to tap it in with a small leather mallet. It was great for "prefab" work. I think the machines were made by a company in Ohio but I'm not sure on that." —@dougtripp2431
"Both circles are cut perfectly round with one tool. Then the hexagon acts like a spring holding it tight forever. Over time it will reshape the wood, but initially they just hammer it in and done."
"My grandfather showed me this technique 20 years ago, and said it was an outdated technique that was no longer used in most construction as it just no longer served a purpose. He called it a Hex ring brace, and stated it was used primarily for door, and window frames to keep the frame together longer.
It was also sometimes used in canvas frames as well, however it may be called something different by canvas framers. He told me it was no longer used as it was inefficient in modern construction due to the time needed to make it. It was quicker to use nails, or screws in more modern homes, especially during the contruction booms after the various wars that occurred. He said the last time he actively saw someone using it other than himself was during a very wealthy mans home construction, and he wanted it as intricately constructed out of wood as possible, and it was during the 1960's.
I only got to see and learn about it out of sheer luck as someone had crashed their car into someone's home, and I got to help my grandfather repair it. The house was from the 1920's, and it was the only reason I got to see it, and ask my grandfather about it. He literally said "Holy shit, I haven't seen this in decades!". lol" —@jacobd.2941
"There were several iterations of things like the ring used years ago. The purpose being old homes lacked footers, many homes were built on piers and those with a full perimeter foundation were laid right on ground.
Due to this, the structure would move seasonally; summer months with increased humidity would cause lumber to swell and push joints, winter months with colder, dryer air and fireplaces for heat would dry the whole house allowing for joints to open up.
Adhesives were limited to hyde glues that lacked strength so builders developed systems to keep meters tight for the life of the joint." —@davidhorsley1149
Mystery solved. No, they were not smarter or more thoughtful than today's carpenters; they were solving problems with the technology they had.
100-year-old crappy miters, as Jonathan sees on his own house from less than a decade ago, are not found by historic carpenters because everything else about those crappy-miter houses was crappy, so those houses fell down a long time ago.
As he points out, carpenters who preassemble trim are generally better and always have been. Today's carpenters use pocket screws because it is super fast and reliable. Also, as David Horsley pointed out, our adhesives are much better than they used to be.