I like to make tables of things that help me around the shop. A while ago I posted one on template guide bushings, now I’m presenting one on rabbet bits.
Rabbet bits are handy addition to your collection of bits. They come as individual bits and are sold by the large diameter of the cutter and the depth of cut they do. Of course they can be purchased in both ¼” and ½” shank size (sorry metric users, I have no idea how your bits are sized). They are also sold as “kits” where additional bearings are included with the bit to give you several depths of cut from the one bit. This also means you will be changing the bearings to suit your needs, and trying to keeping track of what bearing gives you what depth of cut.
Before we go on, the depth of cut sometimes mixes people us so take a look at the first attachment.
The major diameter of the bit come in various sizes, I personal have 4 different sizes. My largest is a 1 ½” followed by 1 3/8”, 1 ¼, and 1”. The bearings are from 1 ½ to 3/8”, so you can see you have a lot of choices. If you can it is nice to get sets that use standard size bearings so replacements are easy to find. You can also purchase bearings to expand a 4 piece set you purchased to an 8 piece.
Please note the table in attachment 2. The first column is the bearing size. The major diameter of the bit is the second row. The remainder of the table shows the depth of cut by combining the bearing and bit.
Let’s say you have made a 1 3/8 hole and now want to make a rabbet to install a flush mounted clock face that needs a 1 ½” hole. The difference between the 1 ½ and the 1 3/8 is 1/8”, this means that you need to remove 1/16” around the smaller hole. You have the 1” major diameter bit so you need the 7/8” bearing. Now let’s say that you have the 1 3/8” bit and need to have a ¼” rabbet to mount a mirror, again a 7/8” bearing.
Some of you were thinking why in the world would anyone want such a small rabbet bit, I would have got the 1 ½” one, now you know one reason. A second reason is that a 1” bit fits in the 1 3/16 opening in the sub-base so sometimes you don’t have to change sub-bases to do rabbets.
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