ATC Adapter for AVID 4 by 2 Machine with 3HP GMT Air Cooled Spindle

I am toying with the idea of adding an Automatic Tool Changer to my Avid 4 by 2 machine. Since I am a hobbyist who typically does only 4 tool changes per project, I am considering adding an ATC Adapter to my existing air cooled 3 HP GMT spindle. I have read that it is not common to add the ATC Adapter to a fan cooled spindle.

My questions are:

  1. Has anyone on the forum done this?

  2. Results / experience?

  3. Does the Adapter interfere with cooling?

  4. How much air volume is used to change a tool, 4 or 5 tool changes?

  5. I prefer to use a portable air tank and not hook up to my compressor, so how big an air tank would I need for 4 or 5 tool changes? 5 gallon tank? 10 gallon tank? Larger?

Having some facts / information based on your experiences would be very helpful.



Personally I would spend the money on a ATC capable spindle as the retrofits are always a compromise.


Before we get there, let’s ask the real question;

How many runs a day do you do as a hobbyist?

ATC are expensive in more ways that you realize. They also make machining more complex.

Thanks for responding! I have watched several videos reviewing the process of installing and using an ATC Spindle so I think I know the complexity plus benefits / disadvantages. I am just trying to collect specific info about the four questions that I have not found enough information on to make a decision.

The cost of an ATC at around 4K is not worth the benefits I would get, but the cost of an Adapter for my current spindle would be around 1K and that gets it in the ‘consideration range’. Just need good info on those 4 questions.

So enlighten me on “ATC are expensive in more ways than you realize”. It appears that the setup can be complex and maintaining the offsets could be problematic plus it takes a little space on my machine. But once all the setup work is done, it should be “faster sailing”. Or not? Enlighten me on the “or not”.



Which adapter are you considering? Can you share a link so we can better help you evaluate?

There are several Adapters listed at the end of this article that focuses on ATC spindles. Have not looked at any in detail. I am just at the collecting info stage. Once I think it makes sense, I will dig in and look at all of them.


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Forgot to add the link!!!

Wasn’t it Robert Burns?

“The best laid plans of mice and men often go awry.”

I am make a 10 tool retracting carousel and dust manifold so just be advised I am “motivated” to get everyone I can into an ATC system.

The system I use is based on the ISO30 tool holders. A decent ISO30 with acceptable runout is $150.00.

The carousel has 10 slots. If you just have 10 tools you have $1,500.00 in tool holders and you haven’t even spent a nickel on an end mill yet.

I bet you think you are just going to change the tools in those 10 holder, don’t you? Yeah, you will try it a few times until you learn you are spending more time keeping those tools calibrated than you would spend with that wrench on the non-ATC system.

Then there is the simple fact the tool holders only last so long. That taper will get marred and the pull studs will pop off and the tool will fall out at high RPM and skitter around you shop. Blah, blah, blah.

This one is my favorite, you will be cutting along and not notice you lost a few steps on your Z axis and when the tool change comes along and you will rip the tool holder clamps off the machine or worse. You will be lucky if that taper survives in that scenario too.

Anyways, you get the idea. Add on top of that the constant calibration and maintenance and you will have your hands full. The stock AvidCNC is a wonderfully simple machine. Not much to really go wrong on them. Not hard to maintenance either.

Do post the link to this retrofit you are thing about?

oh, lastly, “I prefer to use a portable air tank and not hook up to my compressor,”

Yeah. Get a compressor. There is absolutely nothing fun about ripping the core of your spindle out because you ran out of air.

Those others can increase your runout. They will also not survive a crash.

Personally, I would recommend the CNCDepot S30C. I have crashed, blown up, fried, whatever and mine is still running.

Thanks for making that list of “Or nots”!!!

I like to run every scenario thru my head before I turn on any machine and your list helps with what can go
wrong with an ATC Adapter. So far, I have had no accidents or messed up any tools / equipment in the 60 years of working with a range of tools / equipment - well maybe one mistake with a hammer head mower tractor attachment - Lol!

Your list gave me some things that I have to study in more detail too, like the tool holders - I have seen them for a lot less but have not studied cost vs quality.

Any idea how much air a single tool change uses? I would have the air tank mounted near the CNC machine with a pressure gauge attached and visible. I know how much pressure is needed to change a tool but nothing about volume of air.

I have a garage full of compressors but have reasons to use a tank.

Thanks for taking the time to “enlighten me” - really liked your approach of “what can possibly go wrong”!

Thanks Subnoize!


So that leads me to believe that my GMT spindle with an ATC Adapter could potentially increase the possibility of damage to my GMT spindle with the Adapter vs without the Adapter in a crash???

I wasn’t worried about you. I like to warn folks about the fact these machines have no brains. They will do exactly what you tell them to do. You tell it to cut itself in half, it will faithfully perform that task without asking why. You? You would ask me what I was smoking…

Most will use a constant feed of air to cool the bearings. I have a 60 gallon 15 CFM and it runs about every 10 minutes with the S30C. The others I cannot comment on. Count on about 5 CFM or there abouts.

I will put it this way, my system has 2 pressure sensors. One is for system pressure (aka, is the compressor on?) and one for the drawbar (the drawbar state). The reason for two sensors is the repair bill from crushing my carousel. It had the pressure it needed until it didn’t (aka, the pressure was 100 PSI until I activated the drawbar and then it was less than 80 and the drawbar never released the tool).

I would also recommend the tool length sensor or a “breakage” sensor. This will catch some of the lost steps problems or other issues like plastic dust shoes melting and making it lose steps in the X and Y. :stuck_out_tongue:

I just fried my first NEMA stepper ever a few months back. The coupler came loose and the spider twisted up and pushed the shaft of the stepper crooked. The motor will still turn but makes awful noises.

Now imagine you are moving at 18,000 RPM and not 300 RPM and you strike something hard enough to knock that attachment crooked?

We have the same philosophy about 'machines have no brains"!!!

I put people in that category too, sometimes! Lol!

You have given me a good idea of risk associated with an ATC - , what type and results. That is a big part of weighing the benefit of getting an ATC Adapter with the cost / potential problems.

My initial feeling was that an ATC Adapter would save me a little time and hassle as the major benefit. Now I know the other side of the coin.


I have actually thought about waring some sort of body armor at table level in case something catastrophic like you mention happens! Lol! But, I think my fat layer will protect me somewhat!

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There is a time and place for a tool changer. Personally, I just don’t see that GMT spindle being retrofitted and performing well enough to justify the cost. The additional fragility and the loss of possible tool height would not be something that I would be happy with myself.

If I could leave you with one thing, save your pennies for that S30. Its just a well built spindle and the best part is the customer service. They will respond quickly and they are always about helping you.

PS. and buy a compressor! :grin: Get a Quincy, they are American made.

Thanks Subnoize!!! Instead of spending about 4k on a ATC spindle or 1k on a spindle adapter, I think I will get a laser attachment kit and expand the size of my 4 by 2 table to 4 by 4 or 6!!!

Expand the table size, skip the laser.

You should pay me all this cash I am saving you :grin:

Actually, you told me to get a 4K ATC spindle!!! Lol!!!

I need the laser more than the larger table because I want to engrave roads and streams on the 3D topographic maps I carve. I have a couple lasers but need one on the Avid machine to follow the topography to keep the best focus of the laser beam.

Here are a couple photos of some of the kind of work I do…

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$4k? That is what you would spend if you just bought the spindle and left it in the box.

Nice examples though.

Go post your intent in the laser topic. I know it seems rather dead over there but the folks are still around.

So you were going to make me spend even more than 4k - Lol!

I have the laser mostly figured out - just need to finish getting some of the parts and install it. I will check on the laser topic though.

The decision now is there have been more powerful LED laser’s introduced. I only need a 7 watt but if one of my other cutting lasers dies, then I should probably get the 15 watt one as cutting backup, but not sure that the AVID machine will move fast enough to engrave light lines with a 15 watt one.

Maybe this forum will have info on that!