303 stainless steel

[BigSki]

Does anyone have a decent amount of experience with this? I got a 6' stick of .250 diameter to make some lower links. I ran my RPMs low, like around 250 with an easy pecking feed and cutting fluid and I was still destroying drill bits .

I was using a #30 for the tap hole for M4 x .7. I never got close enough to run a tap yet, I've never worked with this grade before, only some 416 which was harder than this but at that time I had carbide tooling. This time, only regular HSS jobber drill bits.

Any insite would be appreciated, I'd like to finish the links using this since I've already paid for the material.

[RCMFMaxxMan]

From what I remember from school, stainless work hardens badly. I don't think pecking is recommended. You don't want to stop in the middle of a cut if you don't have to. Did you start with a center drill and/or smaller bit? I work with 304 for my builds with just a hand drill, a set of good HSS bits, a center punch, and some cutting fluid. I start as small as practical, continuous cuts, and work my way up to the final size. Seems to work for me.

Disclaimer: I'm nowhere near what anyone would consider a machinist, so I could be right, partially right, or completely wrong. ;)

[QuesoDelDiablo]

Look into coated tooling and high pressure cutting fluid. Sorry I don't have time to elaborate more but that will start you in the right direction.

[CREEPERBOB]

TiNi coated bits man And plenty of lube.
Wait till you try to thread it .

[BigSki]

I found some Ti coated stubby #30's in my stash along with some BoeLube. I'll give it another go on Thursday. The BoeLube worked wonders when threading titanium, maybe it will help a bit with this "free machining" SS.

[BigSki]

Better results today. I used 650 RPM for parting, 325 RPM for spotting/drilling and hand tapped the holes. I used pink BoeLube, it made a big difference. The SS was peeling off instead of chipping off. Ti coated #30 drill bit and a 3 flute tap.





A tail stock that held collets would be nice, but this what I had to work with so I made the best of it. Not too shabby overall.

[Hal]

Nice looking links. If I remember correctly, 303 stainless is better than 304 to machine. 304 has more nickel in it so it tends to be gummier, if that makes sense. Nickel is terrible to machine. 304 is a good choice as the material tends to hold up better sliding over rocks. I personally would use 17-4-PH. It can be hardened after if you want or not. Smaller diameter machining requires higher speeds. I probably would have run the drill in at 1000 rpm, slower will work also but tends to put more stress on cutter. I work on very small parts .020 inch and smaller. We run some of our cutters at 30,000 rpm and flood coolant. Oil will help on almost all machining except cast iron. You might also want to think about heat treatabel steels, A2 and such. After machining heat with a torch and let air cool. Once hardened they slide over rocks much better and hold up better also. McMaster Carr or MSC have a lot of different materials available. Go on line and look for "feeds and speeds" for metal cutting it might help also. Good luck.

[BigSki]

Thanks. The 303 is considered 'free- machining' because of the sulfur added into the blend. I found it a bit difficult at first to figure it out, now I could work with it again and get consistent results. As much as I'd love to try my hand at hardening a material, it's not within the scope of what I can do where I'm doing the work right now, so I just try to make the best of what I have available.