Cutting stainless

[originator]

I need to cut out and engrave some hospital grade stainless and was wondering if anyone could tell me if it is doable with the carbide stuff that I already have. I am working with aluminum now with Micro 100 mills cutting out parts in up to .40 and engraving text. I know the stainless will be tougher to cut through, but if I just drop the feed and reduce the depth of cut, is there anything else to do to avoid wiping out my carbide mills?

[lakeside]

Yes The Tools Your Have Should Work Fine Try 900 Rpm 25 Sfm 1.ipm Use Oil And Do Not Let Tool Dwell On Part Cut .015 Deep

[Mcgyver]

not sure what hospital grade stainless is, if possible life would be easier if you could use a free cutting variety. regular stainless work hardens, so like lakeside says, you don't want to dwell or make little tiny chips - the surface immediately in front of the cutter hardens so you want the cutter getting under that on the next tooth/revolution.

I'd be concerned the work hardening is going to be problem for engraving cutters - if its a V shape, at the end of the V the chip load approaches zero and it is essentially dwelling.

[jaako16]

I work for a company producing high end stainless steel that are used for anything between pipelines to bulletproof vests.
The company also makes high end cutting tools for this type of work.

We use a cutting lubricant (paste) sold under the name ROCOL which is making wonders when working with stainless steels.

The problem is that the machine has to have enough power to run the tool as you have to take really aggressive cuts at low rpms.

Good luck

[spacelysprocket]

when cutting 304 series stainless i always will opt for a lower spindle speed and a higher feedrate, the idea in this is to get any heat produced during the cut to go into the chip, not the work piece, inturn avoiding any work hardening.

[originator]

thanks for the tips fellas. i will gve it a shot and see what happens. the main thing i want to do is get the edges looking nice after the parts are cut out. my limited experience with aluminum is that you must have an entrance and exit path or there is a mark where it goes in.

[ghornseth]

So-called "surgical stainless steel" is nothing more than type 304 or type 316 stainless. Both will machine the same--poorly.

All that the surgeons need is something that is relatively inert for short time exposure to body fluids (e.g. saline solutions about the concentration of sea water) and the ability to be sterilized in an autoclave without rusting/staining.

So, when the door-to-door salesman comes around hawking surgical stainless steel kitchen pots, you can have a laugh.

Good luck with it--I hate machining the stuff.

[originator]

I bought some socalled hospital grade steel today, cut it no problem with some micro 100 stuff. At first I tested some engraving with text, highest spindle speed, very low feed and many 4 or 5 passes to get to .015. The stuff loks great so I am very pleased. I used cutting oil at all times. I then tried cutting out a rectangle in the 16 guage 304 steel, I took 45 minutes to cut a 1 inch rectangle, but want to make sure I didn't damage the .25 end mill. At first I had it around 8000, and the oil was smoking, so I dropped the spindle down till it stopped smoking, 2200 rpm was magic number. I was going at .01 cut per rev to avoid any damage on my dirst attempt.

The end results were excellent. I need to find a way to take the sharp edges off the sides of the rectable piece, maybe just some fine sand paper by hand?

Side topic: what are you methods for applying paint to fill the text? I tried using a Qtip to dip the paint and fill the lines, then wipied the excess with a paer towel. I think there is a better way though, when it dried I had too much smear and had to use a solvent which affected the good paint in the grooves.

[lakeside]

try this 4 flute center cutting endmil .25 dia depth of cut .025 rpm 790 ipt .0007 sfm 52 ipt .0028 ipm 2.1

[anchornm]

Do a search on nameplate paint stick
that should get you close --- paint sticks are the best way to fill engraving in pet name plates. I did a job a few years ago --- we made 1500 sequentially numbered ID plates for computers

Originally Posted by originator I bought some socalled hospital grade steel today, cut it no problem with some micro 100 stuff. At first I tested some engraving with text, highest spindle speed, very low feed and many 4 or 5 passes to get to .015. The stuff loks great so I am very pleased. I used cutting oil at all times. I then tried cutting out a rectangle in the 16 guage 304 steel, I took 45 minutes to cut a 1 inch rectangle, but want to make sure I didn't damage the .25 end mill. At first I had it around 8000, and the oil was smoking, so I dropped the spindle down till it stopped smoking, 2200 rpm was magic number. I was going at .01 cut per rev to avoid any damage on my dirst attempt. The end results were excellent. I need to find a way to take the sharp edges off the sides of the rectable piece, maybe just some fine sand paper by hand? Side topic: what are you methods for applying paint to fill the text? I tried using a Qtip to dip the paint and fill the lines, then wipied the excess with a paer towel. I think there is a better way though, when it dried I had too much smear and had to use a solvent which affected the good paint in the grooves.

[troytoy]

Originally Posted by ghornseth So-called "surgical stainless steel" is nothing more than type 304 or type 316 stainless. Both will machine the same--poorly. All that the surgeons need is something that is relatively inert for short time exposure to body fluids (e.g. saline solutions about the concentration of sea water) and the ability to be sterilized in an autoclave without rusting/staining. So, when the door-to-door salesman comes around hawking surgical stainless steel kitchen pots, you can have a laugh. Good luck with it--I hate machining the stuff.

You're partialy right except that surgical grade stainless is garanteed to be 100% nickle free. The human body can have adverse reactions to nickle, and a small percentage of the population has allergic reactions to it.

[ghyman]

My experience with milling stainless (of most grades!) is that cobalt tooling works slightly better than carbide.
Carbide tends to go from 'cutting OK' to 'broken' pretty quickly; cobalt is a little more forgiving.
I will typically use a fine diamond stone and put a .0005" (max) edge break on the flutes and corners for stainless. That helps to prevent a lot of the edge wear from becoming a problem, and tool life goes WAY up.
The down side is that you sacrifice surface finish a little, and it takes a little bit more horsepower to drive the tool And, since stainless is usually running at low rpm/higher feedrate, that can make a difference.

Just my $.02