A very quick question. I would like to know whether I could cut very thick Aluminum. I’m talking about 2-3 inches or so. I am asking because I want to mill out some AR lowers from scratch. My cutting size is 12 * 19 * 4. I am also planning on setting up a CNC spindle with a PID control loop to make cutting a bit more efficient. So is this possible on this machine especially if I make my DOC very small and my speed very conservative?
Your going to have a hard time finding an endmill that can handle 3" DOC in a small enough diameter.
Would the endmill be the only limitation? I was thinking that rigidity would be the biggest factor here but since my work area is relatively small I hope that it would hold up if I put braces on it.
For my spindle I plan on getting this: https://www.amazon.com/Spindle-Cooled-Milling-Converter-Engraving/dp/B01LNBOCDA/ref=sr_1_3?ie=UTF8&qid=1523062640&sr=8-3&keywords=cnc+spindle&dpID=51U0s8rR0yL&preST=SY300_QL70&dpSrc=srch
The largest diameter endmil that it can hold it 7mm. Are there bits out there than can handle 3" with this diameter. If not, then what is the limit (considering that I don’t have lots of money to spend just on endmills)?
Also, thanks for such a quick reply. I am so amazed how this community remains fast and not toxic like some other communities I have been apart of.
It would be an amazing cut if you did it. I have no idea about the endmills. I have never needed anything other than what is in the shop for the MPCNC. I can tell you I had a 2.5" DOC aluminum job on a Hass mill and it is a special kind of cut. 3 people double checked the CAM before we ran it.
I can also tell you the 2.5" endmill I got only lasted one cut and cost me $80…5 years ago. We chipped a tooth somehow. You will need air, and I doubt it can be done without a few different length endmills to work your way down. A 6" throw will not work.
I doubt this will be worth whatever you might save on buying a pre-made, but I would love to see you try. Build the machine as small as possible, every 0.1mm is going to matter. Maybe just Just keep the final product not the focus, just the cut. I’m not excited to get any press for that kind of use. Hope you understand.
Oh yeah I definitely understand why you wouldn’t want any kind of attention because of this sort of stuff. The price difference is actually very substantial in some cases, however. Thank you for your advice and feedback.
Thanks for your post. It reads like deja vu for me. 
Which PID will you be using?
Making my own with an Arduino and some sort of tachometer
Please do let us know how well that does (or doesn’t) work out for you.
Sure thing. It seems to be the most cost effective way of doing things instead of buying a SUPERPID