I agree with 90% of what you say, as it appears to have good authority. The thing that ran the English out of the steel business was not better steel, but marketing. Sandvik was bigger and had more stuff to offer, better prices. Cost effectiveness of unbreakable steel was moot. The UK steel was definitely better. But do you want to pay 90 bucks for hex bar stock and then trepann, machine thread and ends, and harden? Sheesh! And then you have to ship them across the pond and get the mines to buy them. Tricky.
Betamax was way better than VHS, but somehow the great mediocrity wons out. A Messerchmitt was better than a Yak-21 too, except for the loss rate.
Keep it coming. If I keep pissing you off pretty soon you are going to tell me all there is to know about drilling :)
It appears I was wrong about stellite. It is definitely a cobalt-chromium "steel", (more a metal with minor iron) with moly and tungsten, thrown in. Haynes developed it in 1905 with Deloro. Not that hard in test but harder in wear, as its carbides are the as RH as the H of H. But I had thot Deloro had something to do with the niobium-nickel super alloy turbine blades that will go to white hot with a smile. Maybe they did, but it is not called stellite.
"Many shaft sinkers now using hydraulic jumbos, drilling full face instead of benching. Drill large diameter(6 to 10 inch) pilot hole about 400 feet long as a relief hole then one pass 14 foot steel (yielding 12 foot hole) for blast holes."
I know they do that, but do you trust a sinking cut with only one relief hole? I would tend to use three, can it hurt? Or a tight group of three bull bit holes every six feet. Has to work. The trouble is if one does not go... whereas the way the big blasts work is most of the energy goes into one lift up .. the horizontal surface is 60% of your relief, and the single hole just gets the rock moving.. If you made it three smaller blasts the principle is different.. and the throw is greater too.
I never saw a reliable technique for drifting or raising that did not use a 3-2-1 where three of the holes (the upright triangle of bull bit holes) were relief holes, and the other three holes were blast holes into the flats between the pairs of reliefs. The danger here is you could get melting (or what they call 'freezing') if too much blast energy is concentrated in too small an area. So your blast holes had to be about 8 inches from your faces between relief. It is a balance between enough relief and too little.
EC<:-} |
