Milling Niobium

[balnh]

Any one have experience with this stuff? Got some small parts that are about .55 x .24 x .098. I got a 12x12 sheet .125 thick. Small rads and features no holes. I'm assuming it's kind of gummy. SFM,hss, carbide, coated, uncoated?? This project was dumped on my desk with no one in shop having had to cut this stuff. Thanks.

[Guest]

http://www.espimetals.com/tech/machiningniobium.pdf

[Pilot Plant Supervisor]

Very gummy. We use uncoated carbide because you want a sharp tool with positive geometry. HSS works, but Niobium can be abrasive especially if it is alloyed. Use oil or flood coolant mixed on the heavy side. I would start about 150-200 SFPM and keep the chip load down to .001 or less for small parts/tools. It usually doesn't cut too bad, but can be a challenge to get good surface finish particularly when facing. If an endmill doesn't give the finish you need on the face, try a fly cutter or single flute tool.

[balnh]

Ok thanks parts actually get bead blasted then plated. I have a sample part and It looks atrocious. Material is customer supplied, but I'm told it is pure niobium annealed. I have no way of confirming that. Seems soft though. Thanks for the suggestions

[Pilot Plant Supervisor]

It will be dead soft then. Use sharp tools with lots of rake.

[balnh]

Thanks for the help

[clayallen]

On 6/2/2015 at 9:52 AM, Pilot Plant Supervisor said:

Very gummy. We use uncoated carbide because you want a sharp tool with positive geometry. HSS works, but Niobium can be abrasive especially if it is alloyed. Use oil or flood coolant mixed on the heavy side. I would start about 150-200 SFPM and keep the chip load down to .001 or less for small parts/tools. It usually doesn't cut too bad, but can be a challenge to get good surface finish particularly when facing. If an endmill doesn't give the finish you need on the face, try a fly cutter or single flute tool.

What would you start with for plunge milling a 1/16" HSS endmill in C-103? We are having issues with carbide 4FL tools. They just load up. Switching over to HSS, but need some advice on S&F. 

[balnh]

I’m not familiar with that alloy. For pure niobium I would use carbide if I could, and ramping not plunging. I treat it like 316. Drilling with high speed drills just kind pushed the material and left a huge mushroom. Fortunately I only have to go -.125 deep so I circle milled the thru holes. 

[clayallen]

3 hours ago, balnh said:

I’m not familiar with that alloy. For pure niobium I would use carbide if I could, and ramping not plunging. I treat it like 316. Drilling with high speed drills just kind pushed the material and left a huge mushroom. Fortunately I only have to go -.125 deep so I circle milled the thru holes. 

It has a much higher tensile than pure Nb, and contains Titanium. We are only going 0.06 deep, so ramping is a good option I had not considered. We were able to get a HSS endmill to plunge, but there is a lot of tool deflection. Carbide tends to wear really fast, and galls badly in the grade. So HSS is preferred. 

[Pilot Plant Supervisor]

I agree with balnh, helix mill if possible rather than plunge.