I was trying to mill 0.025" stainless steel with a 0.5mm bit.

General CNC CNC Routers
, ,
1

I was trying to mill 0.025" stainless steel with a 0.5mm bit. I had set up the feed rate slow and would only mill 0.01mm per pass. However after milling the first hole the bit would break. This happened 3 times before I gave up.

Now I am a newbie to machining so I tried to set feedrate and everything very slow, but was unsure if this was causing the bit to get dull?

Another fear I had was the work piece might vibrate and break bit, but since I got first hole made I figured it was not that unless the bit got dull.

Of course I was trying this on a shapeoko which has poor mechanical tolerances to begin with, but was wondering if there was some tricks and pointers to milling with small bits that others could share?

Thanks

2

Heat. You’ve got to cool the bit. And remember, it’s not just feed rate, but also RPM. Heating increases with both. Then there’s the quality of your bit.

3

So it breaks when plunging down to start a second pocket? What feedrate to you have for plunging movements?
0.025"=0.6mm thick…does the part vibrate?

4

Stainless steel work hardens. So you need to use a heavy feed with it. The lighter you go with stainless the harder it gets. More than likely your machine is simply too light to effectively work with stainless.

5

Too much for your machine.

6

What type stainless? 303 is much easier to machine compared to 304 or other types. You really need a much more rigid machine to cut metal. Try 303 if you want to have any chance and use slowest rpm your spindle supports.

7

I make only engraving, You need to go low RPM to make this
But I don’t know the good RPM and speed

8

I’m trying the free 30 day version of G-Wizzard. It’s supposed to be quite good for unusual cases.

9

Hi Trampas, can you give more info on your bit and material. How many flutes is your bit, is it carbide? What type of stainless, is it like 316 or a 4 series? That makes a lot of dicference on feeds and speeds.

10

It is 316 stainless, bit was cheap carbide end mill from Amazon.
Not sure on spindle speed it was shapeoko spindle with no speed control, so fast.

11

@Trampas_Stern Get a “PWM Speed Control”, Cheap or otherwise… I use one with a full size router…

12

OK, your bit is most likely loading up with material. The chip load should be about .002 of an inch per tooth. If you don’t know spindle rpm then the feed will be difficult to calculate. Your machine can do it but you need to have a constant feed to rpm ratio to maintain a chip load of .002 inch or you will be breaking bits.

13

Maybe you can try our special Carbide drill bits for stain steel .

14

@Tary_Tang .o0(I thought it was stainless steel .Why drill bits for stained steel. :wink: )

15

Slow and cold,I machine stainless alot,(in a professional machinist) stainless is tough but gummy it also gets very hard if it get hot. So slow the tool speed down and the feed rate. Use a cool mist unit or a cold air vortex unit to reduce the heat produced by machining.