Hello fam!
I’m shopping for router bits. I know the 1/2" shank bits have less chatter and cut smoother than 1/4" shank bits. But does the length of the bit matter too? I’m looking at flush trim router bits with bearings at the end. One can trim 1" thick material, the other can trim 2" material. I won’t need the extra depth often, but the longer one isn’t much more expensive. So I’d be using the part of the bit closest to the bearing most often, with the router body cranked up about 1" higher (or the base cranked lower, if you like.)
So will the longer bit deflect more, chatter more, etc.?
Thanks in advance!
Longer bits are more prone to chatter, at least as a general principle. It’s especially noticeable with a milling machine cutting metal.
In this specific case I don’t think you’d have a problem with the 2in long bit. In my experience the critical thing to pay attention to is the ratio of the diameter of the bit to its length. A 1/2in bit that is 2 inches long works out to 4 diameters. That’s still quite stiff, and a lot of machining resources will instruct people to aim for 4 diameters or less whenever possible, so that’s not excessively long. Now if you had a 1/4in bit with that same 2" length–that’s 8 diameters, that is asking for chatter, but a 2" long 1/2" bit is not bad.
The second reason why I think the 2" bit would be just fine is because if it’s a flush trim bit then the bearing will contact the workpiece and that helps dampen chatter as well. That’s not quite the same as a plain straight bit where there is nothing to support the tip of the bit.
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Makes perfect sense, as always. Thank you!