Need help, milling 316 stainless steel, 1mm endmill. Keeps snapping.

[GMitchell]

Hi, I'm a hobby machinist, general experience in aluminium and steel. I have to engrave some text into 316 stainless steel sheet with a 1mm carbide ball nose slot drill. They are very expensive, and I have snapped two, now I only have one left. What are your thoughts on speeds / feeds?

Mill is limited to 1600 RPM, feedrates recommended by the manufacturer is 160mm per minute, but the slot drills snap off when I try and engrave at 50mm / minute, I wasn't brave enough to try 160mm / minute. what am I doing wrong? Can someone please help?

Thankyou, GM.

[PixMan]

Your machine's 1600 rpm limit is what's killing you. You say you're using a "slot drill", and I'm not familiar with that term. If I were doing this at those speeds, I'd probably stop using carbide and go with a 1mm HSS-Co (high speed steel with cobalt) 3 or 4 flute ball end mill. A HSS-Co cutter can't run at the same speeds as carbide, but they are a lot less money and have a much-higher transverse rupture strength than carbide.

Run it a touch slower, perhaps at 1200 rpm. Load the tool at no more than .008mm per tooth, so 9.6mm/min. It'll take a long time to get finished, but less headaches and money spent.

[GMitchell]

Thanks, I tried running at 8mic per tooth, 1600 RPM, 12.8mm/min and all went smoothly.

I went through the tool manufacturer's website, and it turns out they had put the wrong data in their recommended cutting conditions!

Sutton tools (a major manufacturer in australia) calls a 2 flute tool a slot drill (cause it can plunge, and cut keyways and slots) , 4 flute is called an end mill but most calt plunge straight down.

I was using a 2flute (slot drill ) ball nose tool. 1mm.

Thankyou for your suggestions and advice, saved my bacon.

[PixMan]

Glad things worked out well for you, and if I helped, that makes my day. I had to do a little bit of converting to come up with my guess of 8 microns per tooth feed because everything in my head is in the imperial inch system.

[ahooper]

I have been having fun myself. I have purchased a Siex SX2 that has a top spindle speed of 2500RPM. I converted it to CNC and it seems to work pretty well with larger stuff...
I have just purchased some 1mm TI Coated 2 Flute ball end mills and am having fun trying to work out the optimum speed and stepdown.

The metal I am cutting is an unknown carbon steel that has not yet been hardened but still the specs say it should be running around 50m/min with a feed rate of 0,01-0,025 mm/tooth.

The I thought the Feed and Speed were the same thing or are they referring to the feed as the XY and speed as Z or is the speed the RPM?.