[ZeroBacklash]

That's a tiny motor. I don't think .25 Nm continuous will be enough to do any real threading.

For this tiny machine do you think 2Nm for spindle is sufficient to do the usual lathe operations and threading. I am also getting a bit confused in spindle motor selection for a lathe what would I need speed control or position control. I was going for a dc brushed servo with a tach, so will this be suitable for the usual lathing operations like facing etc which required speed and the other operations like threading which require accurate sync and positioning.

[hfjbuis]

I would keep the original motor for all lathe operations and would add speed control later. I do not use speed control on my lathe.
I normally run my Nema17 and 23 steppers at 1/8 step to reduce noise. Even then, i can't run them at full speed because i normal have small work pieces. So nema17 for Z and X and Nema23 for the spindle is sufficient.
I don't regret the change to Nema24 for the spindle, but it was after all not necessarily. On the other hand, the price difference is small.
I am not trying to achieve the highest speed. I am glad if it is working. So i can not benefit from the expensive leadshine and others. I use TB6600 steppers bought from ebay and also use the chip in my own designs. I suits my needs very well.
Having separate stepper drivers makes it easy to changing the controller. And even if you later decide for a leadshine driver, the money wasted is small. The same could be said for the controller. If you go for linux you can do it with a cheap BOB. For Windows GRBL is cheap and used a lot. The CNC conversion of my lathe is done for $100,-- and it works very well. I have learned a lot and never regretted it to do it "the cheap way". I make my own gears (and gear cutters) but used the original late gears for the gearboxes. Just to show how (easy) it can be to do a CNC conversion of the lathe.
Your first car wasn't a ferrary, so why should your first CNC build be one. I know you get a lot of response from every body and they "all" are right from their perspective. You just have to ask your self what you would like to achieve and consider what is doable with your budget. In the end, it is a hobby and you do it for the fun.

[ZeroBacklash]

a cnc retro fit in USD100 is amazing. Basically before buying this I had read that PC's cannot handle multiaxes without missing steps so I went in for the motion controller. Also I had gone in for an ethernet one because of USB being more susceptible to noise. Maybe I got a bit carreid away by that. But my intention was to learn from other's experiences. Unfortunately I didn't get this kind of advice earlier.

Also another reason I going for a stronger motor for the spindle is currently I cannot get larger that 0.2 mm cut on the emco unimat on Mild Steel without the spindle motor slowing down. So I wanted to get a stronger one to get more out of this lathe.

So do you use linuxcnc as the software? Also do you think 4kg.cm steppers are sufficient for the cross slide / carriage?

[hfjbuis]

Also another reason I going for a stronger motor for the spindle is currently I cannot get larger that 0.2 mm cut on the emco unimat on Mild Steel without the spindle motor slowing down.

Cutting 0.2 mm means 0.4 mm in diameter. In steel i do 0.2 mm max. My spindle will drop a bit in speed but who cares. As long a the finish is ok. And to get a good finish, i do a final 0.01 mm pass at a low feedrate. I rareley use inserts, basiccaly I use HSS, it is (re) grinded in seconds on a dremel with a cutting disk and the finish is very good. I can cut tough steel like Cr42Mo4 using inserts (CCMT060204) 0.05 mm thicker than using HSS. But in the end, time is not an issue.

So do you use linuxcnc as the software

I tried mach3 and Linux CNC but i found it to complicated for simple jobs. Combined with CAM (Fusion360) it took more time to prepare than to turn. I looked at making an extension for Mach but the documentation was to confusing. Commercial controllers like USBCNC (Eding CNC) where to expensive to start with. So i start building my own CNC controller based on a CNC controller i made for the electronic clutch for my motorcycle. Then i stumbled over GRBL, it had all i needed and i must say I can't do it better. So i decided to use GRBL for controller. Combined with my own software i can do 'Conventional" turning the CNC way without CAD or CAM. For free style parts, witch i haven't made yet, you can still use CAM and one of the available GCode senders.
You can take a look at the software CNCL in the Microsoft store, download, try it.

Also do you think 4kg.cm steppers are sufficient for the cross slide / carriage?

I use Nema17 0.5 Nm for the cross slide (direct connected 110 mm/min) and carriage (20/50 gearbox 300 mm/min), that is enough for me. Also when you make an mistake, due to the "low" force, the damage is low. I have spare Nema 23 and 24 stepper but i am not going to use them for the lathe X or Z axis.

[ZeroBacklash]

I tried mach3 and Linux CNC but i found it to complicated for simple jobs. Combined with CAM (Fusion360) it took more time to prepare than to turn. I looked at making an extension for Mach but the documentation was to confusing. Commercial controllers like USBCNC (Eding CNC) where to expensive to start with. So i start building my own CNC controller based on a CNC controller i made for the electronic clutch for my motorcycle. Then i stumbled over GRBL, it had all i needed and i must say I can't do it better. So i decided to use GRBL for controller. Combined with my own software i can do 'Conventional" turning the CNC way without CAD or CAM. For free style parts, witch i haven't made yet, you can still use CAM and one of the available GCode senders.
You can take a look at the software CNCL in the Microsoft store, download, try it.

Its amazing to learn from your experiences, so if I got you right you have a pc with parallel port and that goes to a grbl controller then a breakout board and then the drivers and the steppers. And you use custom software without going into the hassles of CAM.

What breakout board did you choose to go in for or did you choose to go in for? Also modern PC's dont have a parallel port so do you have a PCI card that you have inserted in you PC? Also are you running on linux or Windows?
Its fascinating that you could get a CNC up and running in as low of USD100.

[ZeroBacklash]

You can take a look at the software CNCL in the Microsoft store, download, try it..

CNCL seems to be good, so all I need to use it is a Arduino Uno connected to a PC (Windows 10). I already have the breakout board that I ordered from CNC drive.Drivers I can possible use the leadshine ones.
I have a few questions regarding this setup.
1. Do you have noise issues, I mean the arduino getting effected by noise from the motors or via USB and it behaving erratically?
2. How did you connect the spindle motor for threading, I believe you left the original spindle motor as is for normal lathe operations and you added another stepper for threading etc. So you connected both via belt drive to the final chuck shaft?
3. For spindle is your existing motor an ac induction motor?

[hfjbuis]

Yes, all you need is an arduino, some Dupont wires for connection and your leadshine drivers. The genuine arduino board is rated for 20V but the ebay boards are most times rated lower.
I don't have noise issues. Keep the arduino control signals and power supply away from the stepper A+A-B+B- and power cables.
Below is a picture of my control board with a ESP8266 for WiFi connection to my tablet, a small adjustable powersupply for the fan on the Y (C) axis, the arduino with a self made shield for connecting the arduino to the drivers, 3 TB6600 drivers and a power supply. The steppers are connected using 3, 4 pin , 16 mm aviation plugs.
On the picture below you don't see a genuine arduino but a self made arduino having a power regulator ( LM7805) that can handle the output of the power supply (24 V). On top there a self made shield for easy connection of the stepper drivers.

The original spindle motor, is used for all common turning tasks. For threading, i activate a 2 (4) Nm stepper by a lever (the stepper also turns de original spindle motor). This stepper turns the gear on the spindle. See the pictures below
Stepper mounted on top of the gearbox, with on top a leaver to engage the stepper


Stepper not engaged


The stepper is engaged, the gear is driving the spindle

You could also mount the stepper in the gearbox and use the tumbler that switches the spindle direction to engage the stepper.

The original spindle motor is a DC motor with variable speed control.
Any step/dir driver can be used for the GRBL controller, so yes, you can use your leadshine drivers.

GRBL has a good Wiki. Look at: https://github.com/gnea/grbl/wiki
The CNC conversion of my lathe is documented. All the info, drawings, pictures and documents are available at: Welkom op www.mwt.messageboard.nl

[skrubol]

CNCL seems to be good, so all I need to use it is a Arduino Uno connected to a PC (Windows 10). I already have the breakout board that I ordered from CNC drive.Drivers I can possible use the leadshine ones.

If you got a parallel port breakout board, it probably won't interface directly to the arduino. I'd look for a GRBL parallel port shield. Should be cheap.