There are certainly countless variables to this stuff, but one simple reason may be that you are getting the O1 harder than the 1095. O1 is a very deep hardening steel and doesn't require as much finite control of temps and quenchant.

it would not be too difficult to get O1 as hard as glass.

1095 and O-1 are an interesting contrast. With both having from .90- .95% carbon they make a good study in simple carbon vs. alloyed steels. A striking difference is the inverse effect that alloying has on heat treatment- the less alloying, the quicker the quench should be but the less picky the temperature and soak parameters need to be, the more alloying the less demanding the quench speed is but the more important it is to have good temp and soak procedures.

For example, if somebody asks me to help troubleshoot their heat treatment and the steel is 1095, I will first look at the quenching procedure and then work back to heating from there. If the steel is O-1, the quenchant is the last thing to look at but immediately start asking about precise temperatures and times used in heat treating.

But to Nicholas’s initial question- cementite (iron carbide) is hard but is a pussy cat compared to more complex alloying carbides like those formed with chromium, tungsten and vanadium, which will laugh at your abrasives. 1095 only has iron carbide, which aluminum oxide can make easy work of. O-1 is loaded up with chromium carbides and, depending on the flavor, a pinch of either vanadium or tungsten carbide. Even in the annealed condition these carbide will resist your sanding much more than 1095s cementite.

The real dream to polish is bloomery steel which has none of the modern additions. When I make that stuff it is cool to be able to shave, chisel and scrape as if it were wood and hand rub a finish in just a few passes.

It's definitely made me re-think my process. I usually get stuff to about 90% before quench and leave myself a little room to work after heat treat. I'm going to take a different route and hand rub to 500 before quench and try out some anti scale products. I've always said hand finishing is the most misrable part of knife making. If I can find an anti scale product that will at least reduce the oxidation to the point where I can rub it off with 500 grit, I'll be pretty happy.

Nick, I finish my O-1 to about 120 on the disc before hardening/tempering. After HT, I finish to about 400 by mechanical means and them proceed to hand finishing. I think finishing to 90% before HT is a lot of work that HT is basically going to erase, and you will be back at 120 or coarser all over again.

BTW, I love O-1. I love the way it looks when finished out. I love the way it performs in a blade, and I love the way it forges. Yeah, it puts up a good fight sometimes, but hey. If it were easy, anyone could do it! I use silicon carbide paper for all grits above 220 when hand finishing this stuff. Aluminum oxide just doesn't cut it (pun intended). <img src=' http://www.americanbladesmith.com/ipboard/public/style_emoticons//rolleyes.gi f' class='bbc_emoticon' alt=':rolleyes:' />