Thread: Noob question about blade size

Hi everyone,

Just joined. Have question about blade size. Have done due diligence in research but apologies in advance if this has already been discussed to death.

I've just come into a Dubl Duck Satinedge in what appears to be all original condition. Measured the blade. It's 18mm from top of spine to edge. In the "The Straight Razor" Wiki 2.2, it says: "an 18mm large blade is called a 5/8." 18 mm = 0.7 inches, whereas 5/8 (0.625) inches = 15.8mm. So why is an 18mm blade not a 6/8 ( = 19mm)???

Would it be because a 6/8 is .75?

Many would also say it is a 11/16 blade

Originally Posted by ace

Would it be because a 6/8 is .75?

Exactly the problem.

5/8 = 0.625
6/8 = 0.75
18mm = 0.7

So 18mm is "closer" to a 6/8, being only 0.05 inches off rather than 0.075 inches...which is what prompted the question.

Originally Posted by Zephyr

Many would also say it is a 11/16 blade

Thanks Zephyr. I hadn't seen blade sizes commonly expressed in 16th of an inch...guess I missed it.

You also have to consider that different people and razor companies measure differently. Some measure from the top of the spine and others measure from where the spine touches the stone.

I've found it much simpler to read the tape measure myself. Ofc that's not helpful, but I'm a little confused by numbers, and wonder why you wouldn't just measure it. Are you curious if the wiki is wrong? Is that the question? Good eye by the way, it could have said 2 inches equals 9/8ths, and I'd have said ok. Lucky for me, the tape measure is never wrong.

Originally Posted by regularjoe

I've found it much simpler to read the tape measure myself.

Which is what I did. The blade measures 18mm. Which is 0.7 inches. Which to my mind is closer to 6/8 (0.75")...but then I read the Wiki, and it said 18mm is a 5/8 (0.625").

Originally Posted by regularjoe

Are you curious if the wiki is wrong?

I'm curious what the proper measure is for this blade. Is it a 5/8 or a 6/8?

I'm not doubting the Wiki, b/c you all know waaaaaay more about razors than I ever will. But I am wondering why an 18mm blade is considered a 5/8, when it's closer to a 6/8. Is that just convention, b/c it's always been that way? Or what?

OK, sorry, I don't know. I read a tape measure that shows eights of an inch. 3/4ths is 6/8ths, 5/8ths is 5/8ths. It'd either be a light 6/8ths, or a heavy 6/8ths, depending on where the tape landed. I didn't contribute to the wiki, and I don't measure in millimeters unless it's a coticule.

Originally Posted by ace

Would it be because a 6/8 is .75?

0.75" is 19mm

@OP not all 6/8 blades were same dimension there would always be some discrepancy in size. Same for all other sizes 5/8, 7/8 etc.