I'll tell you something I do as a woodworker a lot that metric isn't great for: divide by powers of two, three or four. I've got some boards milled up 3/4" thick. I'm going to join them with a bridle joint, that means cutting the middle third out of one and the outer two thirds from the other. So each of the remaining "tongues" are each 1/4" thick.
3/4" is approximately 20mm. That's a nice metric number, a multiple of 10. Let's cut that same bridle joint in 20mm stock. What's a third of 20mm? Can you come point to 6.6666mm on my metric tape measure here?
Don't pretend base ten doesn't do stupid things too.
Can you come point to 6.6666mm on my metric tape measure here?
Yes: For woodworkers, it's identical to 6.5mm, accurately eyeballed at between 6 and 5mm. Don't pretend you're a machinist. Does your tape measure even have a vernier scale. Does it make satisfying clicks when measuring. If you have a slip instead of interference fit just dump one piece in water for a second it'll be fine.
To be more precise, it should be rounded as 6.7 cm, accurately eyeballed at between 6.6 cm and 6.7 cm.
I'll tell you something I do as a woodworker a lot that metric isn't great for: divide by powers of two, three or four. I've got some boards milled up 3/4" thick. I'm going to join them with a bridle joint, that means cutting the middle third out of one and the outer two thirds from the other. So each of the remaining "tongues" are each 1/4" thick. 3/4" is approximately 20mm. That's a nice metric number, a multiple of 10. Let's cut that same bridle joint in 20mm stock. What's a third of 20mm? Can you come point to 6.6666mm on my metric tape measure here?
Don't pretend base ten doesn't do stupid things too.
Yes: For woodworkers, it's identical to 6.5mm, accurately eyeballed at between 6 and 5mm. Don't pretend you're a machinist. Does your tape measure even have a vernier scale. Does it make satisfying clicks when measuring. If you have a slip instead of interference fit just dump one piece in water for a second it'll be fine.
To be more precise, it should be rounded as 6.7 cm, accurately eyeballed at between 6.6 cm and 6.7 cm.