Converting an AMAT25LV

[Lloyd Barnes]

As per the title, the plan is to convert an AMAT25LV. It seems a well trodden path so am hoping with the info available and some nudging back on track where required from you guys all should be well. I do have some questions at the bottom so would really appreciate your comments;
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For info, I'll be machining aluminium perhaps 80% of the time, with occasional steel parts thrown in. Mostly car components for various petrolhead projects. I can always do some of the serious hogging out on the Bridgeport if it becomes a better option.
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Things I've done/bought so far....
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Electronics
• NEMA23 4nm motors for X & Y axis
• NEMA34 8nm motor for Z axis (I plan to add power drawbar etc and had read that a bigger motor would be a good idea for the Z axis
• Digital steppers, 5.6A for NEMA23 and 7.2A for NEMA34
• CP0-10V 4 axis breakout board. Only planning on using 3 Axis initially but wanted to leave option for 4th if it ever became desirable
• 48v power supply for drivers/motors
• 24v power supply for breakout board
• I've added an additional 4 relays and seperate 5v power supply to control box for future upgrades
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At this stage I've pretty much finished up the machine control box. (you'll note from the pics that even if I cant afford a Tormach, I can at least have a fancy Tormach inspired logo? lol)
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The current thing I'm working on is an enclosure. I want a really solid stand (I had the RF30 on a flimsy stand and it rattled like a good un). The plan is that whatever I make will also be bolted to wall/floor. I also want something enclosed to keep the chips down. I've pretty much made the base and am starting to fiddle with the tray and enclosure next.
The mill should arrive in a couple of weeks. I went with Amadeal as the price seemed fair and also they had an R8 version in stock. All of my Bridgeport tooling is R8 and whilst I'd want at some point to dedicate tooling to the CNC mill, seems to make sense to keep options open.
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I do have some questions. Mostly thoughts I've got based around what I've read others doing;
1. I've read that bracing the Z column helps rigidity a lot. It sounds like common sense but has anyone tried it and able to comment or advise on what works best. I've put a box section upright on the rear of the base to give me something to brace to (or could go to wall if necessary)
2. Is it worth upgrading the spindle bearings to angular contact (see next question)
3. Is it worth increasing the spindle RPM? Playing with a feed/speed programme 4,000rpm seems a useful speed to aim for when I'm machining aluminium?
4. If so is it simply a case of swapping out pulleys or will the motor struggle? It's sold with a 1kw brushless DC motor.
5. I was planning initially to run mist coolant although I'll build the enclosure with flood in mind. I understand that chip evacuation is my primary goal with lubrication a second and cooling a third priority. I'll read through other posts but any major objections to mist?
6. I'm a little baffled by the pro's and cons of mechanical limit v proximity sensors? I have some limit switches but if its the right way to go, then happy to ditch them and switch to proximity, or am I getting this back to front and I need both??
7. Can anyone confirm how I should work out the amp setting for the drivers (am I being thick again?!)

Appreciate any thoughts