Over in our tool forum, in the What Tools Did You Use This Weekend thread, bdoell88 made mention of Keo countersink bits, which are zero-flute bits designed to chamfer and countersink holes in a variety of materials.
I also own these bits in a range of sizes, and they definitely do provide great results. I have found that they chatter less than fluted countersink bits, and that they leave smooth edges.
They’re available in different angles, depending on what you want to use them for. You can buy them in 60°, 82°, 90°, and 100° angles, and a range of sizes, usually from 5/16″ to 1-1/4″.
To start, for basic hole chamfering of for countersinking a hole for flathead screws, a 1/2″ countersink with 82° angle is a good way to go. This size, model no. 53512 (more info), can make a minimum cut of 5/32″ and maximum of 29/64″. It has a 5/16″ shank.
Keo countersink bits are made from M-35 cobalt steel, for great wear resistance and use in many different materials, including metals that are typically tough to work with.
They’re available uncoated or with TiN finish, but I’ve mainly seen them uncoated. If you don’t know whether a TiN coating will work for you, stick with the uncoated bright finish style.
If your zero flute bits get dull with use, and they eventually will, you should be able to sharpen and refresh the edge with a small grinding wheel. You should be able to use a Dremel rotary tool, or something similar, with a fine-grit sharpening burr inside the cross hole.
Zero flute countersinks cut slower than other countersink styles, such as single flute or multi-flute ones.
These bits are somewhat pricey. The aforementioned 1/2″ in-between size is $22 at Amazon. For some reason, the 5/8″ size is a little cheaper, at $19, but I feel 1/2″ might be a better general purpose size to start with, unless you know you need one larger or smaller.
Buy Now(via Amazon)
Buy Now(Other sizes)
I plan to eventually talk more about the differences between popular countersink bit styles, but the post idea has been on my to-do list for a few years now.
What’s your take on zero flute countersinks, from Keo or another brand?
Thanks to bdoell88 for mentioning this on the forum! If you haven’t checked out the forum yet, now’s a good time.