OMIO CNC Bearing Hole Issue

I’m having some tolerance issues with my Omio CNC, whenever we are doing bearing holes which in Fusion where we do our CAM there diameter is 1.128, and after machining we are measuring roughly 15 thousands to small each time, any insight on this would be greatly appreciated.

What speeds and feeds are you using? Do you have “leave material remaining,” checked? Are you doing any kind of finish/spring pass after the roughing pass? Is the diameter tool your CAM software says the same size as the one in real life?

Here’s some photos of our setting choices in fusion for the CAM


Sorry for replying so many times it wont let me upload all of them at once since i’m a newer user apparently.

And yes the diameter is matching that of the one in real life

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No worries. Nothing sticks out at me here. Looks like you are not doing any kind of finishing, or spring pass with a very small tool (1/8"). My suggestion would be do do a finishing pass at the nominal size you are shooting for.

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Alrighty we will give it a shot thank you.

I would recommend using the largest tool possible, reduce tool stick out and do 1 or 2 finishing passes at .005" or so material removal for those spring/finishing passes.

From there you can update stock to leave if it’s just too undersize.


We will give it a shot thanks for the input its much appreciated

Our team has been having the same issue on our OMIO recently. Also using Fusion 360. I am curious whether there are any recommendations for climb versus conventional milling on OMIOs to get accurate bearing hole sizes? Thanks.

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I would consider climb milling on a finish pass:better surface finish, as long as your mechanicals are nice and tight!!

If you’re using hsm to clear out the bearing pocket you will need to do a profile operation afterwards to make things their final dimension.

I’m guessing based on your various settings that you’re using hsm.

In my experience you should be using the boring operation in Fusion CAM not the 2D profile operation.

Can’t speak to omio specifically, but make sure your tool diameter is properly set. The description says tool #1,1/8" diameter, but then it says R0.00… (cut off).

Create a test pattern and verify all axes are moving correctly. 2" squares are good.

Most CNC routers will perform best using conventional milling. They are rarely rigid enough to perform climb milling unless it is a very shallow cut. Ymmv.

0.015 stepover is very small for a .125 bit. Consider 40% (.05) instead. Double-check your safe distance, a value like 1/2" is more common BUT the omio may use the setting seen fir something else.

Lastly, find out what the “finishing passes” checkbox does, it may help here.

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