Thread: Table Plasma Cutter for blanks?

I know a machine shop that has a large CNC table plasma cutter. I was thinking about the possibility of razor blanks? I havent talked with the shop yet. I did run the idea past a friend who's been knife making and forging for many years and he expressed concerns about "possible issues" because of the heat of the plasma cutter unlike a water jet. Any thoughts from experienced razor or knife makers on the forum..?

I would think you'd be cutting large, and before any heat treatment, so I think it'd be fine. I also think cutting the blanks is probably the easiest part of the process.

Then again, I know next to nothing about steel.

As opposed to getting steel white hot in the fire when I am forging it?
You'll be just fine, as long as you make blanks and not the final shape of course.

You have to consider the kerf width and the heat affected zones near the cut. You could lose a little carbon in the burn areas. It depends on the steel type, thickness and how fast the PC can burn, too. Definitely before heat treatment though.

I think a member named medicievans hired a shop to cut out his blanks on that type of machine. Might look him up and ask about it.

As other have stated, you'll have a heat affected zone that you should remove because it changes the composition and microstructure of that area, and if you're not carefull you may not remove enough and have that bad area right where your edge is! It's thickness depends on material, material thickness, and machine perameters, but I know we were required to remove .050"-.080" for anything aerospace that was cut via "unconventional machining" on .125" stainless plate. And that's just stainless that wasn't going to be heat treated. Waterjet leaves you with no HAZ but does imbed the granite particles into the parent material. This is easily removed as it's much more shallow. For knives, I much prefer WJ, but in a pinch you can easily use laser or plasma as long as you take that HAZ layer into account.

It's much easier than bandsawing/filing/grinding the profile, that's for sure! It also allows you to cut test peices from mild steel for cheap to test ergonomics and fit prior to cutting more expensive tool steels without wasting much time.

Edit: Here's a good resource that has some basic information on what a HAZ is:
http://www.hypertherm.com/en/media/HAZdefinition.pdf

I think it would be even more important than ever to anneal and normalize before heat treating, due to the high temperatures involved in lazer cutting. Mike or Afisher?

Originally Posted by skipnord

I think it would be even more important than ever to anneal and normalize before heat treating, due to the high temperatures involved in lazer cutting. Mike or Afisher?

I wouldn't worry too much about the rest of the part. It's highly unlikely that it will reach it's upper critical temperature anywhere other than the HAZ, so as long as that area is removed the rest should be fine to work on prior to it's regular heat treatment. Plasma machines are normally using water to keep the rest of the part cool, and lasers (edit) can use nitrogen jets or another inert gas (can't remember) to cool the part as well.

Edit: water as well, apparently http://www.industrial-lasers.com/art...r-cutting.html

Thanks for the responses... Will be debating it.

The main concern is if you're using plasma cutting to actually create a finished knife, because then you will have to concern yourself with the effect of extreme heat near the edge etc. But for blanks there s no s since you'll be removing that part anyway.