JHossom
01-06-2002, 10:43 AM
Well, it's been a couple months now since I began learning what this steel is about. Testing shows it's a great performer, taking stainless well into the domain of good tool steels. It's fine grain makes for a superb edge. 4% Vanadium makes it wear well. Lots of toughness makes it difficult to kill. AND, it's at least as corrosion resistant as 440C. What more could you want...?
Right now, more than anything else I want a bead blaster so I don't ever have to take this stuff beyond 220 grit. I spent TWO full days getting a decent brushed finish on ONE 12" blade. Blades under 6" finished pretty quickly, but as the blade got longer it seemed like I was creating as many scratches as I was sanding out. Plus, while I was sanding out 220 grit scratches, I was creating what looked like 60 grit scratches. I generated more blue language with that single 12" blade than I normally use to get through a whole batch of 154CM. Even CPM-3V is a cakewalk compared to what I went through.
Clearly, when you throw a lot of chromium into a steel like CPM-3V which is already pretty tough to work, you compound the machineability issues. I've not worked with S90V, but according to Rob it's much the same kind of deal, so he takes the blades out to very fine belts before heat treating so he has little more to do afterwards. Makes sense, and I'll certainly do that next time, but I don't think it is going to completely remedy the problem I discovered, particularly when finishing large blades.
The problem appears to be belt loading, the fine grain dust being caught up and trapped in the belt. That in itself isn't necessarily a problem until you make the belt wet, which you often do with large blades, maybe less so with smaller blades. Certainly smaller blades produce less belt loading than larger ones. When the fine steel dust in the belt gets wet, it appears to aggregate into larger particles, which in turn produce those 60 grit like scratches I mentioned. So there I am sanding away with a 400 grit belt, dip the blade in the the bucket to cool it, and next thing I know there is a 60 grit scratch where there wasn't one before. So back to the 120 grit belt and start over.... Lots and lots of that blue language!
After doing that a dozen times, it got to be pretty old. I tried every belt in my shop, and it just didn't register that it wasn't happening with Trizacts which you have to keep dry, because they don't do well with S30V and I didn't use them much. It was only after the second full day on that one blade that it finally clicked as to what was happening. I then started drying the blade after cooling, and the problem finally stopped. Fortunately it stopped when it did, because I was beginning to run out of steel on that particular blade. Here's what I ended up with.
After heat treat, sand with 120 grit instead of the 220 grit I usually use. I then use 220 grit running a lower speed (40%) with a fairly light touch. I then use a fresh 400 grit and literally wear it out on a single large blade, being sure to keep it absolutely dry in the process. I'm basically using the 400 like it is two belts, one fresh to sand with at about 50% speed, and once it's worn using it again at maybe 70% to get me near a finished surface. I then went to a used 600 grit running at roughly 60% and removed the last few visible scratches, after which I brushed the blade out (lengthwise) with 400 grit greaseless compound on a loose buff. Bingo!
The percents are just estimates based on the speed controller on my Bader BIII. My guess is that it will also work at a single higher speed with some playing around with pressure and maybe grits.
Is it worth it? Oh yeah, this really is a very good steel, but it will be a very very long time before I take any orders for swords in S30V. At best, it is 50% more work than CPM-3V (at present anyway), and despite its attractive price from Crucible, it will have to be a premium priced blade - from my shop anyway.
Thought I'd share this.
Right now, more than anything else I want a bead blaster so I don't ever have to take this stuff beyond 220 grit. I spent TWO full days getting a decent brushed finish on ONE 12" blade. Blades under 6" finished pretty quickly, but as the blade got longer it seemed like I was creating as many scratches as I was sanding out. Plus, while I was sanding out 220 grit scratches, I was creating what looked like 60 grit scratches. I generated more blue language with that single 12" blade than I normally use to get through a whole batch of 154CM. Even CPM-3V is a cakewalk compared to what I went through.
Clearly, when you throw a lot of chromium into a steel like CPM-3V which is already pretty tough to work, you compound the machineability issues. I've not worked with S90V, but according to Rob it's much the same kind of deal, so he takes the blades out to very fine belts before heat treating so he has little more to do afterwards. Makes sense, and I'll certainly do that next time, but I don't think it is going to completely remedy the problem I discovered, particularly when finishing large blades.
The problem appears to be belt loading, the fine grain dust being caught up and trapped in the belt. That in itself isn't necessarily a problem until you make the belt wet, which you often do with large blades, maybe less so with smaller blades. Certainly smaller blades produce less belt loading than larger ones. When the fine steel dust in the belt gets wet, it appears to aggregate into larger particles, which in turn produce those 60 grit like scratches I mentioned. So there I am sanding away with a 400 grit belt, dip the blade in the the bucket to cool it, and next thing I know there is a 60 grit scratch where there wasn't one before. So back to the 120 grit belt and start over.... Lots and lots of that blue language!
After doing that a dozen times, it got to be pretty old. I tried every belt in my shop, and it just didn't register that it wasn't happening with Trizacts which you have to keep dry, because they don't do well with S30V and I didn't use them much. It was only after the second full day on that one blade that it finally clicked as to what was happening. I then started drying the blade after cooling, and the problem finally stopped. Fortunately it stopped when it did, because I was beginning to run out of steel on that particular blade. Here's what I ended up with.
After heat treat, sand with 120 grit instead of the 220 grit I usually use. I then use 220 grit running a lower speed (40%) with a fairly light touch. I then use a fresh 400 grit and literally wear it out on a single large blade, being sure to keep it absolutely dry in the process. I'm basically using the 400 like it is two belts, one fresh to sand with at about 50% speed, and once it's worn using it again at maybe 70% to get me near a finished surface. I then went to a used 600 grit running at roughly 60% and removed the last few visible scratches, after which I brushed the blade out (lengthwise) with 400 grit greaseless compound on a loose buff. Bingo!
The percents are just estimates based on the speed controller on my Bader BIII. My guess is that it will also work at a single higher speed with some playing around with pressure and maybe grits.
Is it worth it? Oh yeah, this really is a very good steel, but it will be a very very long time before I take any orders for swords in S30V. At best, it is 50% more work than CPM-3V (at present anyway), and despite its attractive price from Crucible, it will have to be a premium priced blade - from my shop anyway.
Thought I'd share this.