SO3: Holes .050" bigger than designed

A question for you SO1, SO2 and SO3 owners.

I have created a .250 and a 1.000 sized hole to test out my SO3 and on both test holes, they are .050 thou bigger than designed.

That doesn’t sound right, but I don’t know what I am doing wrong.

I used Carbide create and carbide motion.


Yes, that sounds a bit off. Could you please describe your test in more detail?

You wrote “.050 thou”. That’s less than 0.0001", way below what the SO3 is capable of. Do you mean 0.050" (50 thousandths) larger?

What material did you use for the test? What feeds and speeds did you use? What end mill did you use?

Do you have a router or spindle? Which one?

I wonder if this is do to initialization being off (parameters)…


Yes, I probably wrote the size wrong.

I was trying for a ¼" hole (.250).

I was going more accuracy than actually creating something to use.

1st test hole, the diameter measured .300.

Repeated a couple of time all the same.

Then I tried a1" hole (1.000). Same result 1.050

Router Dewalt 611
Feeds and speed, are the stock numbers for a .00625 end mill. I didn’t change anything in Carbide Motion.

The end mill is a .0625 router bit. I haven’t got any actual “end mills” yet.

Hopefully that answers your questions.

Thanks for the help.


Do you have calipers? If so, please measure the router bit.


Thanks Mark,

It’s .125, not .0625.

I will put in the correct bit size tomorrow and see what I come up with.


Three things influence the dimensions of a cut:

See for further calibration, and squaring which relate to…

The third thing which is the elephant in the room — machine deflection and how squarely it is assembled. Some suggested mods at: — that said, it really is astonishing the possibilities which these machines afford — Clockit on the ShapeOko forums was making clockwork mechanisms which one could make move just by blowing on them.

Thanks @mbellon, @WillAdams for the assistance in this small brain fart. Once I put the correct dimension of the end mill and then did a test cut, I came out less than .005 (5 thousands of an inch) off of the correct dimension.

I will do the testing and calibrating of my machine so I know exactly what I can cut and then off to make sawdust!

Thanks again !


A simple mistake that I think we have all made!

Amirite Mark?

The killer for me is mixing up 3mm and 1/8th endmills!

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Its always worth measuring cut width v tool diameter as Will said,I tune a small variance out just by tweaking the endmill ‘size’.

A simple mistake that I think we have all made!

It is all too easy to do.

Given that the measurement was constant, after some thougth, it occurred to me that the tool might not be what was thought.

Knowing the actual size of a tool is critical for precision machining. In machine shops, each job is often costed with new tool costs included - no reusing tools. The old tools are use for machining things flat and other tasks where the diameter isn’t critical to the operation.


That’s a very believable number for the SO3. @WillAdams can provide details of stiffening methods. It’s my understanding that with some work, that number can be lowered a fair amount. Good routers, good collets, stiffening, metal bed…