Hard mill turning in The Shiz - and first use of Intercon conversational

Here's the problem. The loominum bar in the tool holder below is my Zref reference tool (T10). It's about the length of the longest tool I'll ever use, which is generally recommended. But my Martest 3D probe is even longer, by about 25mm. So if combined in the same setup as my shortest tool (typically a stubby end mill in an end mill holder), I will often / usually exceed my available Z movement. That's one of the main downsides of having a turret / knee mill with only 150mm or so of quill movement.

Time to shorten the toolholder, as it isn't really possible to modify the Martest. The ISO40 tooling isn't exactly easy to hold in the lathe, so why not simply mount it in The Shiz, then knife and fork some moves so that I can "turn" it in situ. It's not unusual to do this, so I'm far from being innovative. Makes sense though.

So I could make something up in Fusion 360 ie define a slot and a tool (of the same width), then post it. The main issue being that there isn't any obvious post processor that will generate turning code for a milling machine that I'm aware of. It would take a lot of messing about.

But as I have not yet tried out the Centroid "Intercon" conversational tool, this is surely the ideal opportunity to do so. 

This is what I'm looking at. Martest tool on the left, "Zref" tool on the right:

Approx length of Zref tool from gauge surface, give or take a mm or so:

So that's ~110mm gauge length. I reckon I could possibly reduce this to 95mm if I machine away 15mm, which will just avoid the threaded grub screw hole:

What about feeds and speeds for hardened steel? This is hardened, so I can't just plough into it as if it were mild steel unless I want to get through a load of inserts. Looking on the internet (I lost the hyperlinks and can't be arsed to dig them out again):

Feeds and speeds for hard milling:
For a 20mm diameter, HRC 50-56,

• Speed - 400 SFM = 120 m/min
• Feed - 2% of dia >> 0.4mm on 20mm dia (feed per tooth)
• DOC - 5-10% of dia ie 0.5 - 1.0 mm (stepdown)

Feeds and speeds for hard turning: 

• Speed - 300-500 SFM, so also 120 m/min
• Feed - 2-8 thou / rev = 0.05-0.2 mm per rev
• DOC - 0.08-0.2 mm stepdown

Sounds as if the milling stepdown may be a bit aggressive. I'll go for something like this:

Speed - 120 m/min (1500 rpm for a 25mm diameter)
Feed - 0.1mm/rev
DOC - 0.2mm stepdown. Seems a bit girlie blouse to me....

Feed rate needs to be in mm/min, not mm/rev, so multiply 0.1mm by 1500 (ie need 150, not 0.1(!!), dick head!).

Finally got it set up, although much of the hassle was due to the relative inflexibility of the Intercon conversational tool. I needed to ensure that the stepdown occurred when the tool was clear of the work. I couldn't easily see any way of ensuring that, so I went with the path offered and offset the position to place the moves where I wanted them. So a bit of a knife and fork jobbie but it allowed me to use the Intercon feature for the first time in anger.

Set up the "tool" in the tool library and tool offset table. I've defined the diameter as 10mm here. That's used in the conversational g code generator.

Haha it's got a very big offset, being 109mm shorter than the reference tool. This is also where the speed (and direction) of rotation are defined. If you don't define them here, the g code that is generated won't tell the machine to turn the spindle.

This is the start of the code that was finally executed after some buggerage and air cutting. Obviously it goes on for quite a few lines hereafter....

Setting the "length" of the non-existent "tool" using the tool setting device:

And setting the X0 and Y0 positions for G54. In ended up moving over to the other side of the vise and using a RH tool. That was easier than trying to frig the Intercon parameters to get it to do what I wanted. Obviously I don't want the step down moves to happen with the tool engaged with the work, yet there didn't seem to be a means of telling it where to make that step down.

For later reference, here's the initial overall length:

Here we go. What could possibly go wrong?

Short answer - nothing DID go wrong, although the feeds and speeds were far too girlie, as suspected. The whole thing took over 30 minutes. If I'd been doing this manually I'd have soon run out of patience and turned up the dial a fair bit. But as it was I was able to put some music on and get some other stuff done.

Let's take a look. Obviously you can't get enough of the childish sparky pictures. Carbon steel and carbide tools with high surface speeds make it easy.

Enough of that. The finish was OK. Better at the outer area where the surface speed was greater. Bloody hot, hence the gloves. Would have been cooler and a lot faster if I'd upped the speeds and feeds, mind....

The Zref tool is 161mm from front face (not gauge length).

The Martest measures 174mm to the same feature, although you might argue that the probe tip will be 2mm closer at the zero measuring point. You'd be right but you need that 2mm clearance to avoid the tip getting nadgered.

The new edge is razor sharp, so let's make some more sparks, this time in the lathe!

Here's the final result alongside an identical 16mm end mill holder. The body is about 13mm shorter, judging by the above measurements.

It's generated a fair bit of this fine bum fluff. Obviously if I'd manned up the speeds and feeds a bit we'd be looking at some more proper swarf here.

So - Intercon tried out for the first time. Probably not too bad for simple jobs involving general milling and drilling without the palaver of generating a CAD model and messing with CAM, post processors etc. Probably a bit unfair to criticise it for difficulty in this situation when I'm actually trying to produce a turned workpiece. But the result wasn't too bad at all. We'll call that a success.....