You may not like this, but..
First, almost all minilathe cnc conversions are pretty weak to near-useless, most especially if machining in steel.
There are a myriad of errors and problems, usually because people want to do this this cheap.
Cheap usually makes it worthless, in this case.
The common problems, and why they occur:
First, a lathe is very, very rigid, and very very accurate, by its nature. Its is an absolute, totally required feature in any metal-working lathe, which a 7x may be.
Machining steel requires great rigidity, in about 1% of the use.
Things like boring the corners or ends of holes, in deep bores.
In doing the sharp ends of ouside turning, where the final cut is deep.
In accelerating out of a cut in turning, or threading, where you need a very, very fast pullout, as fast as possible.
To get good results, above all you need great rigidity (not a lot of power. Power is not really a problem.)
The loss of rigidity is small, only about 0.1 mm of flex, or 3-5 thousandths of an inch, but it totally spoils the ability to get good bores, good threads, or good results in general.
This error is further increased a lot by the semi-finished flexible nature of most minilathes.
The 7x series are not really too rigid, are underpowered, and there is a lot of slop in all components.
Each shortcoming is easily repaired with some work, and some few components of not much cost.
The cheap, nasty, poor cnc conversion have these shortcoming in general:
Direct couplers are used, of poor quality, resulting in flex.
Steppers are used, of low quality and low voltage. Even worse, they are direct couplled.
Resolution is low, and thus achieved results are very, very poor.
The breakout boards are very bad.
They dont have a good, clean stable pulse train.
The pulse train is mushy, leading to lack of speed and acceleration and reliability. As a result, they need to be run too slow.
Screws are not rigid. These exhibit wind-up (like rubber).
Screw mounts are not rigid. These exhibit flex (like rubber).
Screw mounts are badly made. This results in slop.
Voltages, when used with steppers, are too low. Thus you have low acceleration and low speed.
Stepper drivers are bad (due to using wrong, cheap, drives). Thus results in unreliability at high speed, so you need to run them at low speed.
Thus you have poor acceleration and low speed.
Each problem above is easily fixed by 10-50 in bits and pieces, per issue. Some are fixed by 10-20 pieces in less than half an hour.
This is what you should have:
1. Good drivers, at 48V DC, or higher. An example is the 542 series of drivers. 10 microsteps, bipolar parallel, individually disabled at need, no back emf, soft start, no noise (hirring), adjustable microsteps, 100 kHz top speed at least (when driven with suitable hw board).
An example is the 542 series of chinese microstep drivers. These are good and cheap, and have above characteristics. They also have differential signals.
2. If using steppers, belt drives at 1:3 or 1:2, using HTD 5m pulleys, or better (GT2 or GT3, or T5 metric pulleys. NOT XL, or L series, non-precise belts).
Alternately, thick large rigid couplers.
3. Good screw mounts that dont bend. Test with a DTI and hand pressure. Must not move more than about 0.01 mm with moderate force (10 kg or so).
4. Full-step resolution of about 0.005 mm. This means a belt drive or servos.
5. Rigid screws. Essentially, thicker is better. Go up 2 sizes or more from typical.
6. Ideally, ballscrews. Acme screws will work fine, but wear fast. They will have backlash, but this (mostly wont) may not matter.
7. An ethernet-based breakout board, able to do 300 kHz or better in speed.
At a pinch, 125 kHz like pokeys will do, especially for steppers. Its also cheap.
8. Good crisp signal for threading at wide range of speeds. The only one I know of is servo encoders indexes.
A mushy signal will make it impossible to track threading.