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View Full Version : Metric or Fractional Drill Bits



sequoia
03-05-2015, 09:24 AM
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?

Allen
03-05-2015, 11:11 AM
I use metric bits for dots.

Kekani
03-05-2015, 11:42 AM
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.

Michael Smith
03-05-2015, 11:56 AM
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.

Sven
03-05-2015, 07:26 PM
I have a hankering for fractional drill bits for bushings and such, but get by with metric. When I use brad point bits I make a few turns counter clockwise to score the wood before I drill in the right direction.

Gary Gill
03-06-2015, 12:52 AM
The set of letter and number drills fill in between the fractional diameters.

bluesuke
03-06-2015, 02:15 AM
I like metric for dots and for some tuners you will get a better fit

Pete Howlett
03-06-2015, 02:26 AM
Despite being an imperialist I use metric drills exclusively... Anyone needs 2.5mm drills? I get them in packs of 10...gladly ship to you FOC.

Timbuck
03-06-2015, 03:22 AM
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.

photoshooter
03-06-2015, 05:25 AM
I'm not a luthier but I'm a woodworker. In the US and Canada Lee Valley (http://www.leevalley.com/US/Wood/page.aspx?p=42247&cat=1,180,42240) 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 :)

Hluth
03-06-2015, 08:52 AM
McMaster-Carr probably has the largest selection of drill bits on the planet, and you can buy them individually. http://www.mcmaster.com/#

Titchtheclown
03-06-2015, 12:05 PM
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

Kekani
03-06-2015, 07:27 PM
Despite being an imperialist I use metric drills exclusively... Anyone needs 2.5mm drills? I get them in packs of 10...gladly ship to you FOC.

Brad point?

Pete Howlett
03-06-2015, 10:31 PM
Sadly no but a sharp jobber drill works fine..

Kekani
03-07-2015, 04:12 PM
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 ;)