1205mm vs. 0.492"

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qquake

qquake

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I've been looking at the Nouveau Sceptre kits. The description calls for a 12.5mm drill bit. But the instructions call for a 0.492" bit. I looked it up, and 12.5mm is 0.4921". Does 0.0001" really make a difference? I already have a 12.5mm bit, I'd hate to have to buy an expensive 0.492" bit.

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Broadwell Nouveau Sceptre Gun Metal and 22kt Gold Fountain Pen Kit

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I routinely drill blanks where the pen kit calls for a .375 drill with a .394 drill. And have even done some at .394 where the kit calls for .360. That's .020 to .030 oversized with no ill effects. I'm not recommending this, but just using it as an illustration that .0001 is not relevant (and with wood, likely not even measurable). Normally you need a precision reamer to get a hole within .001.
 
I believe the 0.492 is just the conversion of the 12.5mm dimension to inches. Your inch options are either 31/64" or 1/2" with the former too small and later too big. The 12.5mm is the "Goldilocks" one that is just right.


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More4dan said:
I believe the 0.492 is just the conversion of the 12.5mm dimension to inches. Your inch options are either 31/64" or 1/2" with the former too small and later too big. The 12.5mm is the "Goldilocks" one that is just right.


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Click to expand...
0.492 bits are available though. I bought one for this size kit before I finally bought a set of metric bits. Now I use either the .492 or the 12.5, whichever is closer at hand at the time.
 
In this video, there's a comment that runout measured on a drill press of .001 or .002 is "pretty good"... meaning it's often worse. That implies a hole made by a bit marked .492 may vary between .490 and .494 anyway...


But you probably can't see that extra couple thou from the road :-)
 
IF your bit is truly .492", your hole will be a MINIMUM of .492. Wobble may INCREASE a hole, it will never decrease the size of the hole.
 
Edgar said:
0.492 bits are available though. I bought one for this size kit before I finally bought a set of metric bits. Now I use either the .492 or the 12.5, whichever is closer at hand at the time.
Click to expand...

Yes, PSI has them listed, but they're out of stock. Like I said, I already have 12.5 and 10.5 bits, I'll use those.

www.pennstateind.com

492 in. (12.5mm) Brad Point Bit

.492 (12.5mm) Carbon Steel Drill BitYou can use a 1/2 drill bit with brad point, but this 0.492 bit provides a better fit when gluing drilled blanks onto the tubes. Same as 12.5 mm.
www.pennstateind.com
 
A tenth (of a thousandth) precision is beyond the capability of any woodworking and most metal working tools. Also beyond the ability of most of their operators to achieve even when the tools can.
 
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