I will be constructing my first forge ever. I will use a 5 gallon bucket, and I see that Kaowool blankets are expensive considering the shipping. If I use 1 inch 8#, 2 feet x 25 feet long I would have much too excess (3X?). (I plan on having 3 inches insulation so my heating chamber is around the
350 cubic inch size. If I use the 1/4 inch 8# roll, it will work out perfectly. Is the 1/4 inch hard to handle and install? Is one smarter to cut it into lenghts that fit each circumference? Or should one install it in a continuous roll and really be careful to keep it tight? How about cutting 56 doughnuts (11.5" x 3"), (12 without the holes) and installing it in that manner? Burner hole could be a bitch. Any tricks, such a using a hole cutter ( running it backwards ), to make the burner hole ? Sure will appreciate any advice, before I botch up the works.
I've always used 2" blanket, one layer. If you can't buy it cut, you can always build and sell forges (I've sold maybe 15-20 of them). Great for tailgating--bring a couple of forges, sell them for $300 (if you do a really nice job) and you have pocket money to spend on everyone else's tailgate stuff.
If you have to use the 1/4", I think you're going to need to put some kind of stiffener on it, maybe with some on an intermediate layer. Satanite is what I've used. You really want to use this on the innermost surface anyway to lock in any particulates. I think you'd have to cut each layer, rather than do it in one roll. Try it with a long piece of corrugated cardboard. I bet you can't get it tight enough in one piece.
I'm not liking the donut idea. I suspect keeping them in place would be a long problem, and you'll have a lot more wasted material. Cutting them precisely would also not be any fun.
Burner holes--again, I've only used a single layer of 2", 8 pound/cubic foot density. What works really great is some kind of thin wall tubing the same outside diameter as your burner. Just twist it against the insulation until it cuts through. What works best for me is a length of thin wall PVC tubing. Don't get crazy making teeth on it; just the roughness left from cutting the tube with a hacksaw is plenty. I think if you used a hole cutter it would snag rather than cut.
So far as I've read, they haven't found any specific lung problems with unused refractory ceramic fiber insulation. After it is fired, I think it can develop a small percentage of dangerous to breath stuff. New or used insulation, my habit is to work outdoors, with the wind at my back (if you have a respirator, it doesn't hurt). It is an easy enough installation to be careful without being a big hassle. 3M recommends washing your clothes when done (just so they don't sit around spewing particles indoors).
If I have poured a fireclay floor, or used Satanite, I let it cure at room temp overnight, then I put an incandescent light bulb inside and brick up the ends (no energy saving fluorescents!), again overnight. Then I fire it for the first time outside to let any loose junk blow out somewhere other than in my shop.
Dont bother. It becomes even more obvious, when you have any part that has a single bend in it, that the hole in the back is an elusive target. Forget all about getting a part with more than one bend in it through.
My suggestion is an openable front that you can lay the parts across, between the forge mouth and a firebrick or two. Same heat, easy to see and place. Large bent items are easy enough to accomodate, as well.
The only time I see a hole as an advantage is when you are restricting its use to making billets of pattern welded steel or similar ops, where you will not have to deal with bends at all, let alone more than one.
I made a forge with a hole in the back, and won't again. Far easier to deal with laying the long bar across the opening.
I'm assuming that the forge is based on a tube. I've made both kinds, and the tube forges are way easier to make. I've also done a relatively narrow gate (two 18" halves to it); all the scrolls were done in my little 5 gallon forge. Admittedly, some were pretty tricky to get in there, but it worked. Careful planning of what you do first, sometimes you have to put extra bends in places that will be easy to clean up later.
No sign of it here, I checked my filtered mail too. Email can have mysterious delays, but they're pretty unusual. Your email address is now in my whitelist, if you want to try email@example.com once more.