"Michael Koblic" wrote in news:gfqg26$ui6$ snipped-for-privacy@news.motzarella.org:
A water-jet would be far superior to a plasma for cutting blade shapes from already-tempered metal since there would be no heating of the material and, thus, no loss of the original qualities which prompted the project to begin with.
The drawbacks to using a water-jet are, of course, the expense and finding someone that has one that will take the job.
I have no direct experience with plasma cutting. How deep does it heat the material? Also, cutting the blank is only the beginning - there is (I assume) a fair bit of shaping and grinding to come, all of that generating heat.
Are you not pretty much committed to some sort of heat treatment at the end? Or is the material property irretrievably ruined by the plasma cut?
Plasma cutting produces a very narrow heat-affected zone (HAZ), which should produce only a minimum of upset to the existing heat treatment. It will be so shallow, if properly done, that you'll grind the HAZ away in the process of refining the shape and sharpening the edge.
As someone else mentioned, though, the consumables cost of plasma makes it a premium process and you'd have to judge carefully if it's worth it for this project.
About the need to re-heat-treat: As Larry mentioned, saw blades of any quality are preferentially heat-treated in a zone that extends only a short way back from the teeth. You aren't likely to get a usefully heat-treated knife blade out of a sawblade as it is. The blades are made of high-carbon steel, or high-carbon alloy steel in the case of better ones. Some blades are made of a 400-series stainless, which usually isn't as hard as good carbon-steel blades. I had one of these I bought from Sears in the late '60s and I finally got rid of it because of its inability to retain sharpness.
So you probably will have to heat treat them after cutting out the shapes you want. Any of the steels used for wood saws can be re-heat-treated without complication but it's going to be a tricky job anyway -- not because of the heat-treating itself but because long, slender shapes like knives have a strong tendency to warp when they're quenched. There are some ways to work around this, which you can learn from some of the knife-making sources.
-- Ed Huntress
I plasma cut armor plate and hot and cold rolled steel, Al, and copper.
AL is the nicest if thin - vaporizes the metal. When the air is dry.
The steel is melted and vaporized - very fine iron grains are spread about. The air drives the molten metal that isn't vaporized away from the base metal.
The metal gets to 3-5K degrees. It blues HRS 3/4" or more from the cut. Armor plate is about the thickness.
Mart>>> A water-jet would be far superior to a plasma for cutting blade shapes
My small air compressor may have been the reason the tips burned. The plasma cutter at night school ran a lot longer on a set of tip parts despite student abuse. I have a larger compressor now but it still needs work, like rings.
I am a very satisfied user of 1 mm cutoff blades in a 125 mm angle grinder, they last much longer than thicker blades and cut faster. I have a few 3 mm blades left which will probably never be used.
Alan
PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.