Sharpening Centre Bits

I was recently asked for a link to a video on sharpening centre bits, and a quick look on Youtube didn’t turn anything up. I popped out to the workshop tonight and made a video on how to sharpen them. Its quick and easy, and any single cut file will do the job.

I do not recommend them as you first/only set of brace bits, but I would probably recommend them as your second. They are often referred to as batwing bits, and the average ebay listing does not name them at all. The easiest way to get a set is to go on to ebay, search for auger, limit it to collectible tools, and then quickly scan the images. You can usually find a decent set at a low price quite quickly.

Centre bits excel at cutting wide holes, and drilling thin stock, or close to edges where the snail of a Jennings/Irwin auger might cause a workpiece to split.

Despite being a far older design, Centre bits were still being produced long after the Jennings and Irwin augers came along. This is from a 1965 Marples Catalog.

A plated brace (looks 1800s to me), with countersink bits (top centre), shell bits (left), reamers (bottom), and a set of centre bits (middle right). Notice the notches in the shafts of the centre bits. Braces like this locked the bit in place with a catch which grabbed the notch. The location and size of the notch was not standard. I have plenty of bits like, and most work in more recent braces just fine. If you are interested in lesser known brace bits in general, I gave a talk on them for bench talk a while back https://www.youtube.com/watch?v=qKdIYOQL00s

You want a single cut file for sharpening these bits.

For normal augers, invest in an auger bit file. It makes it a lot easier, particularly on smaller bits. Workshop Heaven, Fine Tools, Lee Valley and many other retailers carry them. Only a few years ago they were quite hard to find.

Finally click on the image above to view a demonstration on how to sharpen them.