What size fly cutter for tramming/waste board leveling

I need to tighten my tolerances on my cutting depth and am looking to level my waste board. I’m more concerned with accuracy than cutting time. Is a fly cutter the best tool for the job? Will I get a more accurate or smooth surface using a larger or smaller bit?

Thanks in advance for any advise you can share.

I just used a 1/4" square end mill which worked great. Since you’re taking off so little material you can run it with a fairly high feed rate.

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I use the Freud 16-106 mortising bit with a 30% stepover. It produces a nice finish. Not a fly cutter by trade, but close enough and the trim routers can handle it.

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magnate 3305 1 1/4" diameter


I used a 1/2" two-flute router bit I had around. As other have said; take light passes, light speed with a pretty aggressive step over and it goes pretty quickly.

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Thanks everyone. Now off to work.

Just to close the loop on this, there are some suggestions on the wiki: https://www.shapeoko.com/wiki/index.php/Calibration_and_Squaring_the_Machine#Fly_Cutter to which I’ve added @fiero1’s suggestion.

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I tried a 3/4" cutter and a 1/4" endmill. I liked the finish from the 1/4" endmill better. I just set it to cut 0.05" deep with a 0.2" step over and run it at 200ipm. It doesn’t take that long and looks great.

The larger the bit the more you will see issues from flexing or your spindle being out of square.


Expensive, but worth it.


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I can’t believe I didn’t tram the waste board at the very beginning. WOW, that made a huge difference in the accuracy of my cuts!


I’ve got one of the very old original Shapeoko 3 machines that’s been sitting idle for a few years. I’m back at it again and relearning some/most things. What’s the largest waste board that I can install and run a leveling program on it to take full advantage of the limits on this machine? Probably be using a 3/4" router bit.

I would recommend drawing this up by jogging around and making notes on the positions as the machine moves.

I wrote a bit on it at:

Thanks Will. Using the rapid positions, I was able to get travel on the X axis of 16" and Y axis of 14" clear, That’s adequate for my purposes. Thanks for your help.

Hi again Will. I’ve been playing with the numbers a bit more and came up with, I think, more definitive numbers for leveling the bed on this old dinosaur…lol As you suggested I used the position template in CM to locate the numbers and along with that I gently bumped a bit beyond those settings. Attached is a sketch of the information I gained. First I had to find the center point for the reference numbers. Using the X and Y axis from center point of a rectangle (arbitrary 14"x16’ dotted line on the sketch). This gave me the center point for the layout for the .75 EM I’ll be using.

The sketch shows the .75" holes at each location of the CM template. Using those numbers gave me the size that can be safely surfaced (or cut). I’ve run it through a dry run (router off and bit high above the surface) several times and get the same answer every time… :slight_smile: Hope this helps and be happy to answer any questions anyone may have… Don