Metric or Fractional Drill Bits

sequoia

sequoia

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I need to buy some good brad point drill bits for inlaying shell dots and other fine work. The sets come in either metric or fractional and I can only buy one set. Here is my question: Shell dots are sold stating their sizes in both metric and fractional dimensions. For instance, a shell dot is said to be both 8 mm and 5/16 at the same time. But 5/16th is not 8 mm, it is 7.9 mm and visa-versa. I've tried to measure the dots with a caliper, but it is very hard to measure a small circle with certain accuracy. Are these things manufactured with metric tools or fractional inch tools? I suspect they are made in Asia somewhere (Viet Nam?) where they almost certainly use metric tools.

I know it seems like a small difference, but accuracy in inlay is so important. Should I buy the metric set?
 
Metric bits. Unfortunately, the one I can't find is 2.5mm, so I used a fractional bit, UNTIL, I realized my inlay bit set has the perfect size! What a dummy - been selling them for years without realizing I have the perfect bit for side dots (which are THE most important). Made a jig for the drill press, all is good.

Sorry for the derail.
 
Dots seem less expensive and easier to find with a better variety in metric. The Wood River bit set from Woodcraft is a pretty nice set of brad point bits that often goes on sale. They are sharp and a good value in my mind.
 
The set of letter and number drills fill in between the fractional diameters.
 
On small dots I use the regular type jobber drills..But ! I regrind them and sharpen em with an oilstone to get a really good sharp point.
 
I'm not a luthier but I'm a woodworker. In the US and Canada Lee Valley is a good source for quality individual brad point bits. Metric start at 3mm.
Usual disclaimers; I'm not affiliated. I just send them money frequently and they send me tools and such in return :)
 
For wood cheap drill bits are usually adequate. You can even make your own from an old bolt or nail. Just hammer the end a bit flat and file a point on the end. I have drilled several holes width ways through railway sleepers using a bit made like this because long drill bits are very expensive.
You need better bits = extra expense when drilling into steel.
That being said I use a set of Bosch 2-6 mm quick change brad point bits in my cordless screwdriver for fret dots. They have a really nice point with a small brad point and a raised outer cutting edge to minimise tear out and make a hole with a fairly flat bottom. Cost me $14 Aussie dollars. The cordless screwdriver takes things nice and slow.

http://www.bunnings.com.au/bosch-5-piece-1-4-hex-shank-timber-drill-bit-set_p6320144
 
Last edited:
I'll stick with my end mills for now. There's something to be said for a flat bottom slot, especially on the side markers. I don't know exactly what that is, but I like it anyway ;)
 
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