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By Loring Chien
Oct 20, 2024
Someone remarked how they had a hard time setting bit heights. Here is a brief tutorial on several ways and the best way I have found.
The classic way is to use a ruler and measure the tip of the cutting bit, as shown below:
This is some problems, hard to see, parallax, resolution. And that the tip of the bit is not flat but pointed. The cut will be to the depth of the highest point so you must be able to pick that accurately.
This can be all alleviated somewhat using digital calipers:
The left picture illustrates a pitfall, the tip is not on the plate, even, I fixed it in the second picture. But this is still hard to read and slow to set. The calipers are general purpose tools, so its not ideal.
A method I use a lot is the setup bar, for fixed fractional heights like ½” (0.500”). I use the bar with a straight edge on top (you’ll have to click to download the short video and view it on your computer):
See Video PA200069 in attachments
I swing the straight edge back and forth over the tip of the bit, while I raise the bit slowly until the straight edge hits the edge of the bit and can’t swing over it anymore. Then I back it down even slower until my straight edge passes over. Then I know I am at the right height.
Another specialized but simple tool is a setup jig. This is shown in the following video:
See Video PA200068 in attachments
Again you can see I swing the bar which has a clearance of ½”, over the bit until the bit hits, and then back down the bit until the bar just clears again. These bars are handy and not too expensive coming in fractional sets.
My best height setting tool is one I made myself for the purpose of setting bit and blade cutting heights. Here is a video of it in action:
See Video PA200070 in attachments
It uses a DIY bridge and mounts a machinists digital dial gauge with a flat tip contact. This is spring loaded so it gives me a continuous reading as I am raising and lowering the bit and the flat contact tip automatically finds the highest point on the bit.
One more bonus. On this one I show how I set the height of a roundover bit. The roundover bit as show below can put a smooth rounded-over edge on a workpiece. The bearing sets one intersection perfectly, but the other intersection is set by the height of the bit. Too high it can give a non-feathered transition and too low it results in a step called a bead.
Ideally you want to have the cutting edge (blue arrow) match the base of the router plate or table. Here I show how I use a straight edge ruler to slide back and forth over the lower edge of the bit. I raise the bit until the ruler catches and then I slowly drop the bit until the ruler no longer catches. TBH, this is also something you can eyeball with a handheld router by holding the router plate up to your eye. But this method is easy for use in a table.
See Video PA200071 in attachments
DIY Height gauge links
https://www.sawdustzone.org/forum/di...-have-you-made
https://www.sawdustzone.org/forum/di...ital-or-analog