Increasing strength of steel through rolling

I remembered reading that when I was considering research for this application, and I read it again during that research on RCM :)

It's hard to fathom this idea. I'm not saying I don't believe it, it's just not intuitive. For this reason, I might as well just get some material and cut out a blank (Dremel and a hand drill) and start testing. Propane torch to harden the teeth.

Regards,

Robin

Modern Marvels, episode 487 - "World's Sharpest". I can't find any clips or downloads for that episode unfortunately. Now you've got me drooling :)

Regards,

Robin

Yeah. Trying to keep the cost of each part low.

I looked into that type of work. Bimetal blades are electron-beam welded or laser welded. Both beyond my means at this point, although that doesn't mean I couldn't get someone else to make the coil for me. Shouldn't be too expensive if I'm willing to invest in a large (!) order.

Thanks for your thoughts. Helpful suggestions.

Regards,

Robin

Sci. Channel

"How Its Made"

"Scalpels, Oil Paints, British Police Helmets & Ice Axels"

Whether it was on that program or not, one "documentary" showed double-edged razor blades being made from continuous rolls of stock.

The blades were only seperated when it was time for encapsulation/packaging.

Everything else was done to them while they were still attached to each other.

I know it isn't intuitive, that's why I mentioned it. An easy demo is to clamp two identical pieces of hardened steel in a vise with enough sticking out that you can easily bend them, then anneal one. I posted a demo recently using sheetrock screws, or you could try cheap (carbon steel) hacksaw blades. Heat one red to anneal it, let it cool, then see how they both bend as you slowly increase finger pressure.

In technical terms hardness raises the yield point but doesn't change the coefficient of elasticity. I think hardness restricts microscopic rearrangement of crystal boundaries or slippage planes.

You may have problems experimenting with hardening and tempering unless you have some way to measure the properties of your samples. The standard lab tests are hardness, usually measured as resistance to penetration, and elongation under load. The important number is the Yield Point or Elastic Limit, the force/area where the sample stretches permanently. There really aren't any simple, cheap, accurate ways to make these measurements at home. Common practice is to temper to a color appropriate to the tool's application. What are you cutting?

Jim Wilkins

I've done manual induction hardening using a hand-held unit (with a massive umbilical cord to a large machine) for hardening trim edges and form/draw rads on large stamping dies.

The problem in induction is the cost. The machines are bloody expensive. I'd very certainly investigate going with induction once I think I have something worth selling, but right now it's not worth the money/hassle.

Regards,

Robin

I'll take your word for it :)

I must say, however, that in my case the part runs significant risk of being forced beyond its elastic limit due to its thickness. In this case, strength does have a bearing on rigidity, so I'm not completely convinced that hardness is trivial. This will be a tool that people will abuse, and increasing strength/hardness will have an effect on the tool's usefulness.

I'm actually a tool and die maker by trade, so I have a certain amout of experience with heat treat and dealing with hardened versus soft materials.

I'm at a very early stage, so I'm not too concerned with the exact numbers involved. I'd get a hardness tester of some description, likely before I start building the tooling.

Wood, and at not very high surface speeds.

Thanks for the thoughts. It's very useful to go through the thought processes and try to be cirtical of all these issues.

Regards,

Robin

Sawmill bandsaw blade stock might be practical, then. Perhaps you could find some free dull blades to experiment with. Unlike some metal- cutting blades the set doesn't extend to the bottom of the gullet so if you remove the teeth you have flat material. The set on metal cutting blades is a nuisance to remove because the thin steel doesn't stick to the magnetic chuck of a surface grinder very well. In my limited experience these blades are tempered enough to yield a little rather than shattering dangerously when overstressed.

Jim Wilkins

"Robin S." wrote in news:57414912-1f10-40a6-a2ab- snipped-for-privacy@y38g2000hsy.googlegroups.com:

Why not make your parts out of steel rule die knife?

You can even buy a rule cutter to cut your pieces to size.

I started out as a die bender.

I bought an old Scleroscope of some nondescription for feedback on my heat-treating experiments. It doesn't work reliably on thin material unless there is a very solid support directly under the plunger strike. Repeated readings can vary as much as from 30 to 50 on the scale. I think all errors are low, so the highest reading is most likely valid, but I have no good way to confirm this.

I haven't seen a Rockwell hardness tester for less than $600. Brinell hardness looks like the easiest one to measure with simple home-made equipment.

Jim Wilkins