What causes these patterns on the interior of 410 SS?

rimcanyon · Mar 10, 2021

I bought a bunch of cutoffs of 410SS. I noticed that every single one shows a strange pattern where it was cut. Not the saw marks but the curves that are perpendicular to the saw marks. Blade vibration, like a standing wave?

sfriedberg · Mar 10, 2021

Basically, yes. It's from the saw cutting, not anything inherent to the material.

TeachMePlease · Mar 11, 2021

Every piece of round bar, in any material that I've ever cut on our auto saw looks like that.

Mark Rand · Mar 11, 2021

It's caused by the set of the saw teeth pushing the blade/band from side to side in the cut as the teeth enter the work.

Gordon Heaton · Mar 11, 2021

Thanks, Mark. The question has come up many times over the years and you're the first to offer a plausible explanation!

boslab · Mar 11, 2021

I was told, and it seems reasonable that it’s caused by our old friend resonance, I’ve seen it on billot ( not military grade!) size round and square
It doesn’t reflect the internal structure in any way so the explanation sounds right, the slices were milled or ground, then etched and sulphur printed to reveal the internal structure, cooling, macro segregation, cracking due to casting machine misalignment, roll failures etc, no part of the internal structure was reflected in the eclipse pattern (I invented that one) cause it looked like the time stamped pictures of an eclipse that had just occurred in the late 80s, blade tension seems to bunch the arcs a bit, but as the blade gets hot they move out again, I was told that there was a turning phenomenon that leaves a ring pattern, Whittaker comes to mind but could not find any reference to this
Mark

BT Fabrication · Mar 11, 2021

all my horizontal bandsaws do this. im guessing as the blade hooks a chip it twists the blade vertically back and forth, as hook teeth are wider then the 0.030" blade, it allows it to wiggle side to side. the wavy pattern is probably all the teeth spacing equally grabbing a chip then flexing the other way and grabbing a chip on the other side. probably depends on how tight the guides are and spacing along with not getting an equal cut all the way through the bar stock.

thermite · Mar 11, 2021

BT Fabrication said:
all my horizontal bandsaws do this. im guessing as the blade hooks a chip it twists the blade vertically back and forth, as hook teeth are wider then the 0.030" blade, it allows it to wiggle side to side. the wavy pattern is probably all the teeth spacing equally grabbing a chip then flexing the other way and grabbing a chip on the other side. probably depends on how tight the guides are and spacing along with not getting an equal cut all the way through the bar stock.

Concur.

PHS do a "pattern" too, but waay less obvious off the wider kerf, stiffer blades, slower pace, interrupted passes, and somewhat variable cyclic crank rate across the timing of each individual stroke.

A bandsaw has NONE of those variables, may be a natural "seeker of resonances", but also inherently narrower kerf, high multiple of total tooth-count, self-cleaning of the gullets as it wraps around the guide wheels, hence more consistent, so ... "BFD".

Run what you got!

"Both" can be good?

And an abrasive chopper that can eat even the HARDEST or least-consistent of mystery-metal-nastiest of blade-trashing alloys, however tediously.... even if but a cheap-arse H-F POS? They don't each much cash nor storage space, stashed, after all...

bloomautomatic · Mar 11, 2021

I suspect its caused by the weld in the band not being perfectly straight. That slight bend hits the work and it cuts just a little different. Since it's the same distance apart on the blade, it would make a consistent pattern. Feed rate through the work changes as it gets wider resulting in the curved pattern.

Ray Behner · Mar 11, 2021

It's called "mooning".

thermite · Mar 11, 2021

Ray Behner said:
It's called "mooning".

LOL!

More than one way to "moon", after all. Heard of "tool porn", have we?

But it takes a parting-tool on a LATHE to ... "show us your tits"

CORONA VIRUS · Mar 11, 2021

rimcanyon said:
I bought a bunch of cutoffs of 410SS. I noticed that every single one shows a strange pattern where it was cut. Not the saw marks but the curves that are perpendicular to the saw marks. Blade vibration, like a standing wave?

View attachment 316193

Yup. California.

thermite · Mar 11, 2021

CORONA VIRUS said:
Yup. California.

ROFL!

Precarious geology rings it like a bell ever' time anybody on the LONGER end of a tectonic lever takes a dump?

And here I thot that was just looter politics trembling in trepidation they might NOT get much of anything actually USEFUL... out of a Federal bailout .. they have to fund in indiviual and bizness taxes, anyway!

Yes, there is too such of a thing as a "free lunch!"

Tireless Demlesscraptic Party can even get you the best prices for it!

Jashley73 · Mar 11, 2021

bloomautomatic said:
I suspect its caused by the weld in the band not being perfectly straight. That slight bend hits the work and it cuts just a little different. Since it's the same distance apart on the blade, it would make a consistent pattern. Feed rate through the work changes as it gets wider resulting in the curved pattern.

No. As Mark Rand posted above, and quoted below, it's caused by the set of the teeth, entering & exiting the cut.

Mark Rand said:
It's caused by the set of the saw teeth pushing the blade/band from side to side in the cut as the teeth enter the work.

And It seems as though the pattern left matches the tooth-spacing of the blade itself as well.

And happens on other shapes - Not just round solids.

muckalee · Mar 12, 2021

Has anyone noticed that the marks are at 90 degrees to the saw cut and parallel to the vise jaws? Try holding the shaft with bolt down device and see the orientation of the crescent shaped lines. I first observed these features around 1979 when I first used and saw cuts make be a horizontal hack saw.

thermite · Mar 12, 2021

muckalee said:
Has anyone noticed that the marks are at 90 degrees to the saw cut and parallel to the vise jaws? Try holding the shaft with bolt down device and see the orientation of the crescent shaped lines. I first observed these features around 1979 when I first used and saw cuts make be a horizontal hack saw.

Guess we should start a "museum" of saw-cut art?

Minds me of the lad observed smuggling PANCAKES, uneaten, out of ARAMCO mess, Saudi Arabia, at breakfast time, every dam' day, early 1950's.

US Army CID pounced on him at his quarters, expecting to find the pervert had enslaved and was feeding a local boy or girl in his "service". There could be SERIOUS bloodshed, ever the Saudi's found him out!

No such drama.

He had a GI footlocker full of dried-up flapjacks, his prized ones laid out to admire just as they nailed his twisted ass.

"Isn't is interesting the unique SHAPE each pancake takes as it dehydrates in this hot, dry, climate?"

They flew his ass back to the States, anyway. Just to be on the safe side.

I never thought to ask what had happened to the "valuable artwork"?

One-hump Camels et of em - petrified or never - mayhap?
You'd have to know the durable Dromedary? Tough bastards. Very!

Like to see the voracious buggers try THAT s**t with 4130 pre-hard..or even 12L..?

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What causes these patterns on the interior of 410 SS?

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TeachMePlease

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Mark Rand

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Gordon Heaton

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boslab

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BT Fabrication

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thermite

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bloomautomatic

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Ray Behner

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CORONA VIRUS

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Jashley73

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muckalee

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thermite

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