Looking for CNC projects to do for Christmas, I came across the Vectric Labs Blog where several ideas for Christmas projects were posted. One of the projects that caught my attention was a Tic-tac-toe game by Beki Jeremy in a 2014 blog post. This looked like something I could handle. I could use some ½ inch Baltic birch plywood and a couple of bit changes on the CNC machine and produce one, maybe even two or three.
Tic-tac-toe has always been a fun and often spontaneous game for children and adults alike. Children want to challenge adults to a game; that is, adults who can figure out how to lose, to make the children look good!
According to Wikipedia, a form of Tic-tac-toe may have been played during the time of the Roman Empire, first century BC. The game played at this time went by the name of Terni Lapilli. It is reported that the grid for this game were found chalked all over Rome.
In Claudia Zaslavsky’s book Tic Tac Toe: And Other Three-In-A Row Games from Ancient Egypt to the Modern Computer it is indicated that Tic-tac-toe may have had its origins in ancient Egypt. More recently, the game has taken on several different names including Noughts and Crosses, of British fame (1864) and Tick-tack-toe (1884). The American name of Tic-tac-toe didn’t come about until the 20th century. Wikipedia also reports that “In 1952, OXO (or Noughts and Crosses) for the EDSAC computer became one of the first known video games. The computer player could play perfect games of Tic-tac-toe against a human opponent.” By 1975, MIT students used Tic-tac-toe to demonstrate how a computer made almost entirely out of Tinkertoys could play the game.
Often the best outcome for two good players is a draw. If you really want your head to spin on your shoulders, delve into the combinatorial of Tic-tac-toe, the possible board layouts and game combinations. Look at the strategy of winning or obtaining a draw by choosing the first available move from a list in Newell and Simon’s 1972 Tic-tac-toe program. See more Newell and Simon here. But if advanced calculus is not your thing, get Newell and Simon’s list and challenge some unsuspecting five year old to a game of Tic-tac-toe. Or if you want to engage in an experiment to use Tic-tac-toe as a pedagogical tool to teach this five year old good sportsmanship, you could just cheat and beat the five year old.
For this project, I mounted a 2 foot by 2 foot piece of ½ inch Baltic birch plywood on the CNC machine’s sacrificial board. I pulled up the Tic-tac-toe file and checked the various tool paths to make sure it would work with my plywood. I did have to change the cutting depths to 0.51 inches to insure that I could cut all the way through the plywood. As it turned out, it would have been better to set this at 0.53 inches for my set up since the 0.51 inch setting was a hair short of cutting completely through my plywood sample. Other than this change, I used the original settings.
I loaded up the g-code for the profile cuts first and used a 1/4 inch shank 90 degree engraving router bit to make these cuts. Following all the profile cuts, I changed the bit to a ¼ inch shank 0.25 inch spiral up cut end mill to make the pocket cuts. Following the pocket cuts, I loaded up the various g-codes for cutting out the game board and X’s and O’s. These cuts provided tabs to keep the parts together until the parts could be separated with a sharp chisel.
All that remained then was to sand, seal and paint. Oh, and then to challenge my wife to a Tic-tac-toe game. Of course I would go first.