Not really a problem. Turning 303 and 316 stainless steel is straightforward; 304 is more problematic, but that's the material not the machine. I've also turned hardened silver steel (>65Rc) with no problem; although the CBN insert came off rather better than the carbide one. I haven't milled that much stainless steel, but what I have done was fine. I've also milled HSS tool blanks without issues when I need to remove significant metal before finish grinding.

Andrew

on my small WM180 lathe I can handle 316 (with some trouble) using carbide or a freshly sharpened hss tool
What I think is 304 (judging from colour code as was a bin end and also that it was somewhat magnetic but certainly doesn’t work like mild steel seems to chip off rather than peel – 316 comes off as very fine wire) – took out one of my small carbide parting off tools when it jammed snapping the brazing and bending the support (the HSS smaller parting tool was also prone to digging in so I gave it up) though I could take very shallow almost polishing cuts with carbide – guess a narrow cutting wheel on an angle grinder is the best tool to cut it

Edited By Frances IoM on 10/09/2015 22:48:10

Harrison M300 and a Bridgeport with an early (low power) varispeed head and built-in backlash.

Andrew

Super 7 and M300 lathes, stainless not really a problem, but care with the right tooling.

I used to turn a lot of 316 AM stainless with no problems but 316 J turned red with the heat. Completely different metals.

Hey Andrew – Doh, Guess it's obvious, but I never thought of machining HSS cutting tools before, that's smart. Do you use standard carbide cutters or coated / special ones for that (before I make an expensive experiment)

Cheers – Will

Oooops – Trigger Happy  

Edited By Will Bells on 11/09/2015 16:41:28

Will/Ian: You are correct, traditionally grinding was the only way to 'machine' hardened materials. But with the advent of carbide inserts, and more esoteric materials, turning of hardened materials has become possible. The advantages for industry are no grinder required, and parts can be hardened and then machined, ie, fewer operations. For turning hardened silver steel I used an ordinary CCMT carbide insert and a CBN insert. Both worked and left a pretty good finish. The carbide insert looked a bit sorry for itself afterwards, whereas the CBN insert didn't look like it had been used. The trick is to run fast with high feedrates; the CBN insert is very particular in this respect. This gets the metal in the shear zone red hot, so it is actually quite soft. As far as I could measure the hardness of the workpiece didn't change. The downside of CBN inserts is the cost, I think mine was £25.

As for milling HSS I don't anneal it. I use my oldest 10mm uncoated carbide 3 flute slot drill. The machining doesn't do the slot drill any favours, but it is old so I don't worry about it. Although the HSS toolbit is going to be finish ground afterwards the milling operation actually leaves a fairly good finish. Again the trick is to run fast and hard. The swarf needs to be coming off orange in colour, and the slot drill may well be glowing a dull red.

Andrew

I use CCGT 09 inserts with: stainless 303 & 304, titanium grade 2,5 & 9, mild steel, aluminium. All is fine and give a very good finish from a fine cut.

Only problem I've had is with enlarging a 50mm hole that had been laser cut into stainless 304, think I was making 0.5mm depth of cut every pass. I presume it had been hardened from the laser cutting?