Specialized Drill Bit

Or at least one that is semi-specialized.
I need to drill holes in 1/4" thick metal rails, top and bottom to put new pickets in. The design the owners like best involves a countersunk screw on the top rail.
What's the best way?
1. Is there likely to be a bit for metal that will combine drilling the through hole and the countersink part, the same way there is for wood?
2. If not, I can do the operation in two steps-the through hole first, then the countersink portion.
3. In either case, how do I control for depth for the countersink part, so the top of the screw ends up being flush, or nearly so, within paint thickness?
4. Also, the countersink should have the same angle as the screw itself. How difficult will it be to match?
5. Any suggestions for suppliers? HD and similar stores probably won't have the bits I need.
Thanks,
charles
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Outlets that sell metal working supplies have them.

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Maybe a center drill would work for you? Google "center drill" for examples. They are for metalworking. You are correct, you will not find them at HD.

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check out one of those step drills. the angle might not be perfect but it might just work. they cut very fast and easy to control the depth Mike

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Charles Bishop writes:

What species of metal?
Wide selection of bits here:
http://www.use-enco.com/CGI/INSRAR?PMSECT 00000606
Use a center punch to start the hole.
Use cutting oil and the right bit rotational speed.
Use a drill press if you have one. A good drill press will have a stop setting to get the countersink depth just right.
Your screws probably use a 60 degree included angle.
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you'll need to determine the angle of the countersink. the most common are 90 and 82. you can get chamfer tools accordingly. an easy place to find them is at www.mcmaster.com
To control depth, if not in a drill press situation, you'll need to cut and try. bill

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snipped-for-privacy@earthlink.netttt (Charles Bishop) wrote:

Following up my own post with additional information and thanks for the input so far.
This work will be in the field, on (E) steel railings. The steel is flat stock and is 1/2" thick. I'll need to drill a through hole with a chamfer(?) to include the screw head so it is flat to the top of the bar stock. Bad ASCII art follows:
_______ _ _ ______________ \\ / \\ / || 1/2" || Steel Flat || Stock _________||_______________
In woodworking they have bits that will drill and countersink in one effort, and I'd like the same for the steel. The wood bits can have a "stop" added to the bit so it isn't countersunk too much, and again this would be more efficient than doing it by eye.
The center drill mentioned might work for a two pass attempt but the shaft isn't long enough to go through the 1/2" steel. Same for the step drill.
Again, this is in the field, so a drill press won't be available.
Thanks for the help.
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