@George_Allen for my 4th axis rotary, I use a 11:1 gearhead. Rotary doesn’t need to rotate very fast and it requires relatively high torque so it doesn’t move position under cutting loads.
@Jim_Fong ok thanks. That makes some sense.
@Jim_Fong Do you know how I might go about adapting the small diameter ballscrew end ~7.5mm to a wide diameter ID (~12-12.5mm)? I have the z-axis motor connected to the ballscrew with a pulley 1:1 and the motor fits perfectly, but the diameter of the ballscrew is too small. Currently, I am using a nylon spacer to bridge the gap, but I’m afraid that won’t last long.
@Paul_Frederick I think I just set it up for the first selection on the driver for now. Does 400 pulses per revolution sound right? I need to go back and study that. I wasn’t going to go many microsteps at first.
@Alex_Paverman did you know that Mach 3 and LinuxCNC are forks of the same NIST EMC project? One big difference is which platform each forked project targeted. Mach runs on desktop Windows and LinuxCNC runs on Real Time Linux. Having a Real Time capable OS is generally considered pretty important with computer control. Except for the completely ignorant. Which I’m suspecting you are one of. Change my mind.
@George_Allen What you need to do is set the scale of your machine. Scale is just how much your machine moves a step. You can calculate it or measure it directly. Usually you start out by calculating it, using that, then measuring what you actually get and adjusting your scale to suit. When what you measure jives with what you’re using you’re done. Some folks get very involved with scaling their machines though. What they do is called mapping lead screws. A machine’s scale is determined by a motor’s steps per rev (degree angle), the step sequence you use (microstepping), any gearing between the motor and your lead, and the pitch of your lead screws.
@George_Allen I have a cnc lathe so I would just make a adapter out of some round steel stock. Might want to check around your makerspace and see if any member has one that can make it for you.
@Jim_Fong Thanks. I’ll do that.
@Paul_Frederick , I won’t! I feel so lucky to be enlightend in your proximity… It seems like you know everything about everything. Thanks again!
But let us be civilized people and let aside the mockery. Ok, Linux has the premises to be faster, I give you that. And what to do with it as a DIY-selfer?! I currently use 2m/min feed (with wood) not because the cinematics can’t give me more, but because I can’t get more 24k rpm from the spindle. Do the math yourself for usual 2-4mm mills. So, what should we do with such speedness given by Linux?! For one Linux might be better, for other Windows. But judgement might be based on other criteria than ‘speed’. We, all ‘other mortals’, don’t need to hear, again and again, how imbecile we are using Mach3 and not LinuxCNC. And, please find that I am using Linux in multiple ways. But not for CNC. And I am still happy!
@Alex_Paverman well for one you can network transfer files with Linux and it is not a security risk. Also you can support something besides the hegemony of closed source proprietary commercial software. Further it is not Mach 3 that is letting you achieve your claimed speed. Something that that you’re not disclosing is going on as well. My guess is you’re using a third party external pulse translator a la Smoothstepper. Which cost more money. LinuxCNC rejected supporting those for philosophical reasons. What is the point of making a machine controller when you need another controller? Am I getting warm?
@Paul_Frederick you cant be more wrong! I use a common PC (WinXP), a common (4 usd) breaking board and a licensed Mach3 (175USD). And, of course, the drivers (chinese ones) arround 15 bucks a piece, I do not remember exactly. And that’s all! And it is the pure truth! I simply don’t understand what are reffering to. And I can’t do 2.5m because mechanical reasons, not electric ones. I recon that I had to reduce the acceleration to get 2m/min… But in practice I found that, anyhow, it’s useless to have more. Yet, for G00… As for ‘supporting’ a commercial software, I think it is totally acceptable to pay a (really!) small amount for something it helps you to make money. Those guys had to live too.
Yet, that doesn’t apply to something like SolidWorks which is like 10k usd. 
I am available to continue this debate but I think we should open a special thread for not ‘poluting’ @George_Allen 's one! Sorry George!
2.5m/min isn’t that fast and well within the capability of Mach3 parallel port step output.
I do 45khz on Mach parallel port. Linuxcnc on the same hardware is similar step output speeds.
On a quicker machine you can get Linuxcnc to run a bit faster.
45khz with 16 microstep 1.8degree motor is 848rpm
Using a 5mm pitch leadscrew will be 4.2m/min. No problem.
Linuxcnc can use Mesa fpga step pulse output boards. This is similar to any number of step pulse adapters for Mach3. Even Linuxcnc parallel port has a limit and external hardware is required for high step rates. Servo motors with really high encoder resolution would fall into that category.
@Jim_Fong Do you know offhand what the pitch is for RM 1605 ballscrew? Is it 5mm hence the 05 in 1605?
Yes, the ones on the table are 2010
@George_Allen oh good 10mm pitch means you don’t need to spin a stepper very fast to get decent rapids.
Faster you spin a stepper the less torque is available. That is why using reduction is not beneficial for stepper motors. Use reduction for low speed, high torque applications such as rotary.
500rpm = 5m/sec direct drive.
If you use your gear 15:1 gear reduction, you will need to spin that same motor 7500rpm which would be impossible.
@Jim_Fong No, my table seems to travel well…even with TB6600 drivers on both 425 oz-in steppers
@Jim_Fong what kind of feedrate do you have to maintain if you are milling aluminum?
@George_Allen I only mill aluminum with my cnc bench mill. Since I don’t have flood cooling and max spindle rpm is 2500. Feedrate are under 500mm/min.
I don’t mill aluminum on my gantry router.
I thought spindle speed would need to be slower than that unless you had special milling tools