When you isolate the bearing on a router bit you are putting the bearing at zero with fence or to say flush with the fence.
You are taking the bearing out of play so to speak.
Or you want the stock to run true with the bearing and the fence.
The purpose ▼
Some times you don't need to use the bearing and that's when a fence will come it to play or you want to make a smaller cut and just use part of the cutter on the bit.
Let's take a T & G bits (Tongus & Groove Set) the default is 7/16" deep let's say you want a 1/4" deep slot ,you would isolate the bearing in the fence and just use 1/4" of the bit to get what you want.
You have now isolated the bearing.
Definitions of isolate
A substance/item that has been separated/removed from a combined mixture.
Pat Warner suggests that the bearings be removed and only be installed when needed and then removed again, he mentions the short life of these bearings and adds this time counts even when the bearing isn't touching the work.One more reason I don't like the bearing touching the work when using a fence is any inconsistancy it the wood will be picked up by the bearing.
I would not remove bearings from any router bits, it's true that most router bits now come with a bearing(s) some are on top/center/bottom of the bit.
When you isolate the bearing you have taking the load off of it so to speak but it will still spin at 20,000 rpm but free of any load.
Some bits can not have the bearing removed like the T & G bits because they are being used a spacer for the cut and a stop point (guide).
But if the bearing is in place it will help with the snipe at the end of a pass that's to say you will not have a nick (dip) at the end of the stock when coming out of cut.
It's true that some bits have bearing on them for just the hell of it.
Plus If you take the bearing off the bit you take a chance that you will lose it and they are not cheap to replace not to talk about the screw that holds them in place.
A screw that's not tight will work out and take off across the shop or drop down into the router motor.
It's true that bearing have a short life but if you isolate it , they will last longer.
If the bearing is isolated right it will not touch the stock and can't pickup and errors in the stock when you run the pass. (like a nick in the stock or knot holes ) and the bit will/should remove the nick.
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