Big Barn’s Retirement Farm Shop

[dstig1]

Yes, if I had a plasma table, I would have used that...or a water jet...or a wire EDM...or investment cast it... But like most of us, you use what you got. I got some leftover scraps and a mill and that is about it other than some grinders and a bandsaw for metal work (and a couple welder options). Cutting a slot out with a small bit would be another good way to do it with CNC, but no way I could make a decent rounded end like that manually. I know it is possible, but I am not that skilled, nor that patient. Plus the application is a slot "about the right size" to hang some long tools out of the way and not an inserted buried lifter on an injection mold... And yes, "you don't mill" sheet metal but again you use wha'chu got. And I used a ton of oil. At times it got so hot that even the oil was flashing off That was a hint.

I got the bit used from a guy reselling a bunch of resharpened HSS stuff for like 5 or 7 bucks, so it was not a financial issue but it would have been nice to have the bit around for any future need. I'll live... and I learned not to do what I did ever again! I started off at about 200 rpm (~5/8" dia bit) but it seemed too slow so I ramped up to 600. Perhaps I should have stuck with 200?

 

[the old grind]

You likely could have bumped the rpm up to 1k with the 5/8" HSS cutter. (300 series SS?) I like the fixture for the milling job.

 

[dstig1]

Yes, 304 14 ga. I would have said that I was running too fast as it worked better in the beginning when I was going slower RPMs.

 

[the old grind]

Your feed rate could have been much faster at higher rpm. Chips may clear better and less time in the cut makes less heat and smoke. If the mat'l was just wood you'd want to spin that cutter at 2k and get it over with. btw, I based my suggestion on 150 SFM, at the low end for 304 (150-250) and IMO a 4-flute would have served you better. (no plunge) Results matter. Nice job.

 

[Kyle_in_Tex]

I believe his tool was just high speed steel HSS. 40 SFM or less if so. I tried to cut up an old restaurant worktop made of stainless.....with an O/A torch....needless to say it didn't work too good.

Your feed rate could have been much faster at higher rpm. Chips may clear better and less time in the cut makes less heat and smoke. If the mat'l was just wood you'd want to spin that cutter at 2k and get it over with. btw, I based my suggestion on 150 SFM, at the low end for 304 (150-250) and IMO a 4-flute would have served you better. (no plunge) Results matter. Nice job.

 

[dstig1]

Yeah O/A only works to cut regular steels, so that probably made an awful mess...

Yes my bit was HSS (defintely WAS being the operative word as it is now a pile of slag...) and it was the case i made earlier of use whachu got. It was a one-off and not production. And a manual machine. No way I could run high feed speeds realistically. My knowledge of cutting 304 says low RPM, go slow but always take a chip or it will work harden. And plenty of oil.

 

[the old grind]

50 SFM is too low for SS period. Use higher SFM/rpm next time and read your chip for infeed as always. Your cutter will run cooler if it's in & out of the cut quicker. (proof in the fixture burning even w/coolant) Won't know 'til you try if there's another time.

 

[Kyle_in_Tex]

Here are hss drill speed recommendations. And this is probably with coolant.

 

[the old grind]

Thanks for that. Too many charts/calculators with different specs for 300 series SS. My bad. (Milling 14ga isn't done that often.) btw, don't think for a minute that I don't burn up a lot of tooling on ferrous metals.

 

[TMGT]

Thanks for that. Too many charts/calculators with different specs for 300 series SS. My bad. (Milling 14ga isn't done that often.) btw, don't think for a minute that I don't burn up a lot of tooling on ferrous metals.

I use to do a lot of drilling in stainless pipe with hss annular cutters, high SFM is definitely not your friend! Unless you enjoy the fight and have extra tooling.

I hate running stainless in a manual knee mill, the cutting window is pretty narrow and they are typically just not very rigid/tight.
End up breaking things when it grabs!