This is not a good idea, as others have said. Yes, the Shapeoko can give you nice control over the Z-height, but in all other respects if you are doing router table work, you should use a router table.
If your main concern is the expense of a router lift, what about one of those digital height gauges for 20 bucks?
@CNCNewbie Donāt you just love it when threads go off topic without moderation?
I read your requests for
Routers of any kind can inadvertently āgrabā a particular grain structure in wood even if youāre carefully feeding it. (Iāve done that.) The shaft on a good router can be bent. (Iāve seen that.) The router in your CNC (unless its a spindle) is not very robust mechanically. After all, it was meant to be used in a totally different mode than your CNC is being used for. (Hand-held trimming.)
If youāre willing to risk damage to your CNC (much more expensive than a table-based router) then hypothetically maybe try it. 
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Let me give you another example for why your idea is a dangerous accident waiting to happen, so, let ME be the devilās advocate here!!!
I was building a bird house with my grandson the other day, so I figured instead of having him swing a hammer to nail the sides together, risking him hitting his thumb, I secured a hammer in a bench vise, and had him swing the bird house with nails that are 1st pushed into the wood to get them started. That didnāt turn out very well!! You see, itās very difficult to see each nail and hit it directly on the hammer this way. He ended up destroying the bird house, getting frustrated, and give up the whole project altogether!! I also had to take a couple of splinters out of his hands.
Another day, I wanted to cut some potatoes by holding the knife, sharp edge facing up (on the kitchen counter), and sliding the potatoes back and forth over the knife, but wait, why didnāt I think of this before? They make a mandelin slicer that is, err, also rife with emergency-room-related accidents!!
I would say that EVERY power tool has its safe or dangerous aspects when compared to others. The old Radial-Arm saw was more dangerous than a Table Saw, in that instead of the saw blade being mostly UNDER the cutting surface and the workpiece over the blade, it is not so for a radial-arm saw, thus inviting disaster by having the operators OTHER hand on the side of the blade. Do people use these old saws today? Yes, but given there have been many safety recalls for radial-arm saws, Iād stay away from them. Todays miter saws are still dangerous, and deserve the fear-of-injury level respect, but the blades are shielded more than those older radial-arm saws.
I donāt really comprehend your insistence on being āa devilās advocateā repeatedly. We should learn from othersā experiences and advice!
Bottom line is, engineer or no engineer (I am one, too), Youāre better off using a tool as intended!!! There are many reasons why (design, physics, and otherwise)!
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I apologize if respond here is like tearing a scab off, but I feel it necessary to counter this echo chamber effect here. All the rebuttal here is mean respectfully. After all this should be what a community forum is where different ideas can be presented.
First while there is appears to be a consensus of feeling here that using a CNC in this configuration is unsafe. However, outside this community I find a different reception. Bot all thought it was a good idea but they were more willing to discuss how the idea could work. Therefore my conclusion is that it is not a bad idea but an incomplete idea.
Second, I am not an inexperienced woodworker, Iām more a weekend amateur who has been doing it for over 30 years. I may not have the depth of experience as some of you, but I am no novice either. As for relevant experience, many of the āsafety issuesā brought up pertained to the above table router configuration. Based on the speculative nature of your posts, I may have more experience operating an over the table router than many of you. I donāt see that it is any more dangerous than below the table. In fact safer since you can see the cutter at all times in all types of cuts. I believe the reason this is not more common is simply that over the table router systems are harder to build and hence would be more expensive and more restrictive since you donāt have 360 degree access around the cutter.
Third, as for using the āwrongā tool, letās be honest we all do it, use a screwdriver to pry open a paint can (I donāt own a paint can opener). The main reason people are encouraged to us the ārightā tool sometimes has to do with safety but most of the time itās efficiency. How many of you have a bench mortiser to cut square holes? It is the right tool. But a drill press and chisel will do the same, but if you have to do 100 a day. Youāll want the mortiser. But using a āwrong toolā is not inherently dangerous, you must evaluate each situation.
Finally the āwhyā, I see a lot of potential in using this configuration if safety issues and structural issues could be fixed. Iām surprised none of you see it. First, safety could be improved over a router table. The biggest safety issue I believe statistically is kick back. One of the big causes of kick back is taking too much material. With a CNC based router configuration, you could easily make your cut job several passes using the control software to move the spindle precisely relative to the fence. So instead of slotting a 1/2 inch slot, you could make four passes taking 1/8 inch. Second, precision and reproducibility, because it is a CNC you can always reposition the spindle to the same exact position relative to a fixed fence as well as the same height.
In closing there is a word for using an apparatus in a new way for which it wasnāt designedā¦ invention. (Donāt believe me search patent case law for the phrase ānew useā)
Now that Iāve said my peace Iāll leave this topic be.
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Cāmonā¦ Is this real?
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Did I black out and wake up on Reddit?
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If nothing else, this thread made me seriously consider radial arm saws at the local auction. They are cheap (maybe for āreasonsā). 
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I have 2 radial arm saws if anyone is looking for one
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Come on guys. @CNCNewbie is engaging in a serious discussion. Are the sarcastic comments really adding to the discussion?
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Just some more thoughts:
Not so sure about that. There were moulders around a long time ago. Basically a device with a spinning thingie in it, mounted in a table like structure. Just another name for it.
Which is fine. If you feel thatās what you want to do, do it. But it is not a use case by the manufacturer of the CNC and therefore youāll be very likely on your own when it comes to insurance claims etc. It wonāt matter how many people thought it was a good / bad idea.
I feel the drill press and chisel are the right tool, your argument is just about convenience / comfort in this case.
A CNC is intended to move. Anything that moves will be less rigid than something that does not.
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Agree the thread may have gotten a little bit off track and mostly I hope you do not feel like this community is a bad one because for the most part Iāve found it to be very supportive and helpful.
To be transparent with you Iāll share that Iāve also had this thought cross my mind when I first got my Shapeoko Pro however in the end I decided against it which is why I suggested not to pursue the idea. That said instead of just suggesting against the idea Iāll share why I had personally opted not to pursue the idea and maybe you can consider this into the thought process if you decide to carry on.
I considered the spindle to be a high RPM/torque device and in past work experience Iāve worked near high RPM/Torque (mining and exploration) and have huge respect and caution around anything that moves in this way. Iāve seen people with loose clothing get caught and pulled into such things ultimately getting mangled pretty badly. This is why I like seeing safety guards and limit getting things like my hands close to such machines.
When safety guards are not possible then I consider the work envelope the machine operates in. Agree a workshop is full of these type of things but most are either static or operate in 1 or 2 axis. For me this is where the CNC machine differs form a drill press, router table, miter saw, etcā¦ and likely why Shapeoko like most/all CNC manufacturers will strongly advise against putting limbs/hands within the working envelope of the machine while in operation. So if the controller is driving a program or the spindle is just turned to push stock through the spindle my hands/arms are likely going to be in this space. I could not predict everything and accidents can always happen but with most of these machines I control how I operate them and can put my limbs/hands in locations that if it will grab my stock or the machine becomes dynamic under itās own power (ie. mitter saw), although scary hopefully my hands will not be pulled into the moving/spinning parts or the machine will not move in a direction where I am in the way. As for my Shapeoko it operates in 3D space which means if the static spindle/router (static because of stepper motors are holding it in place vs screws/bolts) then I could not predict how or where it would move if it somehow became a dynamic object.
For example when driving the machine using the controller you control the feeds and speeds, tool engagement, etcā¦ with the high precision the machine is capable of which youāve already pointed out. However when hand feeding stock I could not be as precise and would be manually push material through the machine and possibly losing steps possibly making it go dynamic moving unpredictably within the work envelop of the machine. Although I think lost steps wouldnāt necessarily send my spindle flying to the end of an X, Y, Z axis uncontrollably is would still end up with wasting my stock/project. That said Iām more concerned with the circuit my controller is on (stepper drivers) tripping while my spindle breaker is still live. This last scenario is super scary to me because the steppers would then offer zero resistance allowing the spindle to move unpredictably in any direction (X, Y, Z). This meant if I was to pursue this idea I would have ended up figuring out a way to secure/lock the spindle in place essentially making it static like in a router table. Also in doing so would I cause any premature wear and tear on my linear rails (or v-wheels) depending on the how this would be done (ie. pressure perpendicular to rails/axis thus my linear rails). So for me I would have to lock the spindle in place which meant to make any fine adjustments on the fly Iād have to turn everything off, remove or loosen whatever locking/blocking Iād use on the spindle to hold it in place and so on (EDIT: Locking the X,Y,Z axis using some blocks/fastners).
In my application this would have been to cut a profile down a straight edge so instead I opted to use a long fence which I align against the left Y-axis (aluminum extrusion) and milled the other side with the Shapeoko. I then position my stock against this fence and run my gcode/macro which drops the Z-height where I want it (Z-Zero set before running the program) and comes into my stock from the side and then runs front to back as many times as needed. Once the program is done running I then slide my stock back, secure it in place and rerun the same program until I get the full length done.
That said for my use case I found using the fence and sliding my stock back and running the program as many times as needed met my needs (edit: while keeping my hands outside of the machine work envelope while in operation ā this includes spindle on). If this does not work for you I agree the world needs inventors so if you pursue this idea which in the end is entirely up to you then Iād like to hear about how you āwouldā do it.
Final comment in the end I was simply answering the following from your original post.
The price of this router table is way cheaper than the price of an emergency room visit.
https://www.homedepot.com/p/RYOBI-Universal-Router-Table-A25RT03/300234859
Use your CNC router to cutout an adapter to attach your spindle to a table, and be done. Your fingers will thank you for it.
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Hi everyone,
I think we can all agree not to beat a dead horse, Iāll close the topic now.
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