several years ago i was talking to the manager of the department that cuts windows for Light Impressions and he told me when they first got 8ply board they tried cutting it by hand and couldn't even get inch straight, that it takes a commerical product and mentioned a computized laser cutter that they used. I have heard that there may be a Logan cutter available that will cut that ply but have not seen it nor tried it myself.
I found it just as easy and probably cheaper to just have a commerical house cut that size window for me. I tend to use a lot of 8ply boards as i love the look and just bite the bullet and pay the price
I've cut it with my $100 logan mat cutter. That said, not all mat board has the same density. I've used different 4 ply stuff that varied in hardness from brand to brand, bigtime. The stuff I have is bainbridge i believe and may be softer than others. You can cut with more than one pass if you have everything locked down. There is also 12-ply available now!
I cut Light Impressions 8-ply (and one other company's) with a hand-held $40 Logan and a straight edge. No problem, though I have been cutting mats for myself and others for around 30 years.
Making multiple passes is the easier way to do it, as Vinny suggests. I also start the cut early -- cutting about half way into the board, then sinking the blade the rest of the way at the start mark. This keeps the blade from deflecting at the start and gives nice square corners.
I've used 8 ply for anything that I intend to hang, for several years. I don't cut my own mats, but anytime anyone has cut 8 ply mats for me, with anything but a computer controlled cutter, I've not been pleased with the results. I suggest you look at the Frame Destination web site (I believe that they are an APUG sponsor). They do a great job and I think that their prices are very reasonable. I've dealt with them for several years and highly recommend them (usual disclaimer;just a happy customer).
Another application that makes a beautiful presentation is to cut two 4 ply mats as the cover mats. I use a black mat first then cut the white mat with a 3/8 larger opening in both directions. This will give you a nice 3/16 black border around the image with the effect of 8 ply. Robert
You can generally cut 8ply with the same tools that you cut 4ply provided that you have adequate blade depth. 8Ply is just going to be more difficult and generally require more than one cutting pass. For that reason having a more professional level cutter will make the job easier. It is not just a question of the thickness of the material. You also need to consider the quality level of the cuts desired, and the time you are willing to spend to achieve them. I have been to many gallery showings where the 4-ply mats had poor quality corners. If the same equipment and operator skill are used on 8-ply they will look even worse. Since 8ply often requires multiple passes, having good solid stops will help significantly. Custom frame shops typically have $1200 mat cutters, but even then they do not prefer to cut 8ply since it is still fairly difficult to get a real high quality cut.
My company uses computerized mat cutters and we sell Bainbridge 8Ply. The Bainbridge 8Ply is one of the thickest and most difficult to cut. When our older computerized mat cutter was perfectly calibrated and had a fresh blade it was barely able to cut it. We now have much higher end mat cutters we imported from Switzerland that allow us to easily get very high quality cuts.