Replies

1. 
   hammer1 | Apr 06, 2006 07:21am | #1

   For the most part, I use two different types of drill bits for screws. When installing hardware, I often use a vix bit. These are a spring loaded holder for a drill bit. They automatically center the pilot hole and control the depth.

   I'm most likely to use flathead screws that are either driven flush or countersunk. I like the Insty bit system. There is a combination tapered drill bit, held in a countersink that also has a stop collar and is adjustable. Both the vix bits and the countersink combos come in a hex shank configuration. I use a hex shank bit holder in my drill and can change bits by just pushing on the holder. Changes can be done with one hand and the bits are of good quality, replacement parts are available. There are brad point bits, also, and any hex shank bit can be substituted

   I've owned a lot of different countersink drill combos, everything from those flip over types that Bob Villa used to promote for Craftsman, to the Fuller sets. There are different Insty bit components. I use the following. You need to back out and eject the waste frequently to prevent overheating and jamming.

   80138 Instyloc
   http://insty-bit.com/taper_drill_with_countersink.html
   http://insty-bit.com/self_centering_bits.html

   Beat it to fit / Paint it to match

2. 
   Pondfish | Apr 06, 2006 01:44pm | #2

   Get a set of tapered bits from Fuller (buy them from Amazon), or a similar set from Lee Valley.  You will use #6 and #8 screws the most for everyday types of projects, with the larger #10 and #12 screws for heavier work, like for door hinges, etc.

   Each screw size comes in a range of lengths, but which to use is no different between imperial and metric systems (namely, it depends on the work to be done). 

   You didn't ask, but I recommend square head driven screws.  Also avoid the cheaper steel screws as they tend to break easily.

   Recommending the use of "Hide Signatures" option under "My Preferences" since 2005
3. 
   mbholden | May 03, 2006 01:34am | #3

   Claude,

   simplest way is to hold the bit up to the screw, you should see thread on both sides of the bit, but you should not see the solid center of the screw.

   This will make a hole that the threads will bit into.

   If you have a solid shank on the screw, you will have to enlarge the hole to the depth of the shank with a bit equal to the diameter of the shank.

   Then if it has a flat head, you will have to countersink the surface.

   exact drill sizes dont matter, but if you wish to be most accurate, then ask at your local hardware store for a chart that shows the various drill sizes, and the corresponding screw thread that either taps or clearances the screw. They often have these attached to calendars. You can also find this chart in the "Machinery Handbook" or the little books of facts at the tool dealers (usually have a yellow or blue cover and again have a place for advertising the shop - but these are usually sold rather than given away)

   Mike

4. 
   jeff100 | May 03, 2006 02:55am | #4

   Find a drill bit hole size chart, Starrett used to make good ones & likely still do, find which screws you are likely to use and determine on the chart which drill sizes you will need to use for these screws. The chart will show numbered screw sizes e.g. 10-32 (size 10 - 32 threads/inch) and fractional size screws (e.g. 1/4-20) and the drill sizes for drilling pretapped holes. If you want to determine what size hole to drill to clear a screw size, you will either have to mike the screw across the threads, or look up the specification for the thread pitch in a Machinery's Handbook or similar technical source (or internet) and drill slightly oversize, depending on how much clearance you want.

   Aside from that, the most useful drill bits, IMHO..are sharp drill bits....;-)

   Cheers.

   Jeff

5. 
   nikkiwood | May 03, 2006 06:21am | #5

   There are charts that will tell you exactly what size bit to use for screws for various size -- for both wood and metal.

   As a quick and dirty rule of thumb, if I am using number 8 screws, I use a 7/64" bit for softwoods, 1/8" for hardwoods. And then I use a 3/16" bit if I want the screw to pass through the first piece I am screwing to the second piece.

   Does that make sense to you?

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   "It is what we learn after we think we know it all, that counts."

   John Wooden 1910-