Better metal

The scrap of loominum I used yesterday was cut off from  larger piece by hand on the bandsaw a couple of years ago. When I measured it today, the sides were out of parallel by around 0.5mm. Perhaps not surprising it came loose in the vise.

I cut a 25mm piece off a length of 1" x 2" bar, so the sides were somewhat more parallel. I had to alter the model to make it fit in the narrower stock, otherwise I was able to use the same model for attempt #2.

I buggered up my first attempt with the new stock. The feed rate was turned up accidentally and I don't seem to have got the Z axis zeroed correctly. I also found a bit gouged out of the side which I don't understand - rather like a lot of things at the moment!

I double checked the cutting parameters against Sandvik data for the same inserts and did sanity check comparisons against the likes of the Shear Hog and solid carbide cutters. The fact is, you need to run these cutters very hard and they only have one insert. So the racket they make is quite different to (and louder than) the noise you get from an HSS cutter running at (much) lower speeds, often with coolant or lubricant.

I also noticed that I had left the feedrate set to 150%, so even the fairly aggressive setting were being notched up another 50% over what I'd intended. Hmm.

So, with the stepdown reduced to 5mm (over a 15mm depth ie 3 roughing passes), the feed per tooth reduced to 0.05mm (300mm/min at 6000rpm) - and the feed override turned back down to 100% - off I went again. It still flies along, makes a racket and shifts a lot of swarf.

That's better. I used some WD40 to lightly lubricate the cutter, as there were signs of built up edge stuff on the edge of the insert. Here we go:

And the result: 

So that's my first successful bit of metal cut. Total machining time alleged to be around 7 minutes. Chips everywhere - must get round to fitting the guards and swarf tray. There is a bit of a blemish on the side of the "feature" but I have no idea at this stage what caused it. Perhaps later I may have the ability to figure it out.