Niobium machining polishing

Enough with the easy stuff you guys..

Any ideas of how to get a mirror finish on both sides down through a deep (inches) 0.02-0.03" wide saw kerf in pure niobium? It's a through cut, if that helps (hand lapping?).

Best regards, Spehro Pefhany

Reply to
Spehro Pefhany
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Spehro, A slot is going to be a challenge. A little search shows Niobium tends to gall easily, so initial surface finish is going to be important. A reference to a suitable cutting lube:

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I would try to make a flat, snug lapping tool. Perhaps a sandwich with:
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# 4837A11 (various grits available) on the outside of the sandwich, then sheets of .005" shim stock for rigidity, with layer(s) of paper towel in the center for spring.

You don't mention the smoothness or flatness spec, more info would be helpful.

Dave J.

"The Journey is the reward"

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Reply to
Mechanical Magic

The general description of conventional machining is "like soft copper", but more prone to galling with carbide tooling.

We're working on getting the initial surface as good as possible, but it's not going to be good enough.

Thanks, and I guess one would need a fair bit of skill to get good result?

Maybe as bad as half a thou would be okay.

This reference:

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says that it takes more time and care to polish Nb compared to other metals of similar hardness. 8-(

Spehro Pefhany

Reply to
Spehro Pefhany

Is there any way to make it in two pieces that put them together? Anything that can polish a slot .020 - .030 wide is going to be very flexible and you'll be out of the 1/2 thou tollernace pretty quick.

Reply to
Dan

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Just dress one side by hand to achieve the necessary thickness.

JC

Reply to
John R. Carroll

Yes, in theory, but other things will suffer. It's actually wire-cut EDM'd BTW.

Understood. I don't suppose there's any such thing as CNC polishing? All the mold shops I've seen have a craftsman/woman and a lot of abrasive supplies with and popsicle sticks and such like. Best regards, Spehro Pefhany

Reply to
Spehro Pefhany

Ultrasonic polishing has been around since the seventies for just such applications.

JC

Reply to
John R. Carroll

There is EDM "polishing." Most technical molds today ("technical" referring to molds for functional parts, rather than decorative ones) are EDMed to finish. You can get down to 4 microinches Ra or thereabouts.

It's much more difficult with wire, but you can come close. 0.20" slots are pretty tough in themselves, too.

-- Ed Huntress

Reply to
Ed Huntress

(snip)

If you do a search on niobium electropolishing it seems that this is the method of choice for the type of super-conducting gadget you seem to be making.

-- Adam Norton Norton Engineered Optics

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Reply to
anorton

Thanks for the suggestion.

Most of those other guys seem to be making cavities, which are a lot more accessible. Going the other way (and not with Nb), I have not had good luck getting even thickness of plating deep in slots, but maybe there can be some trickery with the electrodes to get the electricity to flow where it is wanted. Best regards, Spehro Pefhany

Reply to
Spehro Pefhany

Can it be Electropolished? I suspect that is going to be one of your few options.

Its used a lot in the body piercing community as studs, earrings etc. Might want to ask someone in that business

Gunner

Political Correctness is a doctrine fostered by a delusional, illogical liberal minority, and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a turd by the clean end.

Reply to
Gunner Asch

I would sniff around the CERN website in Geneva, Switzerland. They use a lot of polished nobium plated metal for RF cavities in superconducting nuclear particle accelerators, and have spent a lot of time developing the technology.

Joe Hwinn

Reply to
Joseph Gwinn

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