The main modification I made is to install a 12,000rpm spindle at the front of the mill for engraving. This works really well. The standard spindle is way too slow for a small diameter cutting tool.

I swapped out the original main 5 amp fuse for a 5 amp circuit breaker. I found that I was blowing a lot of fuses and it was a bit of a pain swapping them. Was simple to swap out and fitted the same hole.

Changing toolholders is easy if you add a spindle lock. Just press in and use a ring spanner to loosen the drawbar. There is a guy who makes these for the M3.

My milling machine started life as a standard Sieg X3.

There was a company called Promica that did a conversion kit as well as sold these as a turn-key unit, which is what I purchased.

There are quite a few videos on YouTube showing their equipment in action.

Unfortunately they subsequently went out of business and I am now on my own! The controller is propriety so when this fails, it will mean a total upgrade, probably to a Gecko G540 like my mini lathe. The machine came with a 4000rpm conversion, but the fastest I can get is about 3400rpm.

I believe that there are numerous versions of the 180mmx300mm (7"x12") mini-lathe, all with varying degrees of workmanship!

After quite a bit of research I found that a German company sells the Optimum lathe which is built in China to their specifications.

The features that I liked:

Since I completely removed the compound slide, I needed a much higher toolpost than is usually used on a lathe of this size.

So, I purchased a 200 series 75x75mm toolpost on Ebay. This is the same toolpost I use on my 1m bed lathe and allows me to share tools between the two lathes.

The bolt holding the toolpost is M16, so I drilled and tapped the new aluminium slide top I made to suit. IMG 1 shows the toolpost installed on the cross slide.

MOV2 shows the first cut! This was only a light cut on 30mm diameter aluminium to make sure everything works as expected.

I used a Fairchild H21A1 photo interrupter to clock the spindle for threading (index in Mach3 language). These are very cheap, so I may use these for home/limit switches as well. I found a simple circuit on the web showing how to hookup this sensor. It needs 5v, so I found an old USB cable, cut off the other end and used the red and black wires to supply the power to the H21A1. For the disk, I made an 80mm diameter aluminium disk 2 mm thick, with a 27mm hole for the spindle, and an 8mm gap milled for the infrared light.

I am not planning on using a positive Z limit switch since I don't see much benefit from this since it all depends on the length of the workpiece. The negative Z axis limit will be installed near the fixed end of the ballscrew. A plastic cover screws over this.

I have a controller that I built a couple of years ago, that has never been used. I was planning on building an engraver, but I found it was just easier to add a second high speed spindle to my mill.

This is TB6560 based and is a budget model, but hopefully it will fit the bill. If not, I will build a new one around a Gecko G540.

I found an an old HP Windows XP computer on Ebay for $50 including 17 inch monitor! I already have a 14" monitor which is fine for Mach3, so I will probably sell the monitor for more than the combined package!

Inputs

There was a nice box compartment under the motor control that previously housed the leadscrew bearing, but is now empty, so I decided to use this to wire the inputs back to a terminal block. It will be easy to seal this box to stop coolant causing problems.

At this stage I will be using inputs from Spindle Index, as well as a combined Limit/Homing switches.

By comparison, the Z Axis is much more straightforward than the X Axis.

I purchased a 600mm long 12mm diameter rolled ballscrew from China on Ebay (Img 1). This included bearings as well as a flexible coupling. There was a bit of a drama with one of the bearings the wrong size, but they promised to send me another one, and I don't need it for a few weeks anyway. Replacement bearing arrived a couple of weeks later.

I used one of the existing tapped holes to locate the right hand fixed bearing. Other holes will be tapped later.

Once again, the internet was my friend and I did a lot of research on how to manage the X Axis on such a small lathe. Some have even put the screw outside the cross slide, but I did not like the idea of swarf getting into the ballnut. So, I found a neat design, wish it was my idea!

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