Machining slots in stainless washers

[fastturbovet]

I have some 1" OD, 1/16" thick (or thereabouts) stainless washers. I machine a slot that is about 1/4" wide and 1/4" deep in them. Right now I have a shaft and I put 40-50 of them on this shaft and put a nut on the end and just load it in my vice. I seem to be going through quite a lot of bits.

I am a newbie at this type of machine work and I am curious what sort of RPM, depth of cut, and feed rate I should think about? I am using a 4-flute endmill and I have carbide and TiAlN (I think thats the name) coated.

Thanks for any suggestions!

[Konrad]

This is something I would machine with a 1/4" wide Woodruff Cutter, http://www.newmantools.com/endmills/emwr.htm
it would speed things up app. 500%
Konrad

[psychomill]

I agree with Konrad. A key cutter (woodruff cutter) would probably work better for your set up. The endmill, since you're cutting on end, is probably moving and slightly spinning the washers. Especially since you're ganging 40-50 of them. When SS moves around, you end up banging the cutter and chewing it up.

[WilDun]

I agree with both answers above.
In a situation like this the good old fashioned cobalt high speed steel cutter will not chip. - If properly lubricated, it will last a long time, and can be sharpened over and over.
For milling, everything needs to be held as rigidly as possible, vibration doesn't help with tool life, also stainless must be kept cutting because, if it is allowed to "rub", it will work harden, (especially 316).
Coated tools (in my opinion) are great till they chip, and then they're finished, - good if you're selling them of course!

[HuFlungDung]

A small stream of flood coolant is almost essential. I'd also recommend cobalt or hss. Start with very sharp, and feed quite aggressively. With coolant, you can be aggressive, without, it will just burn and stick in your tool.

[SRT Mike]

Thanks guys, I will give the suggestions a shot. I do have a woodruff cutter the correct size but I was hoping not to have to use it because it means I need to develop a new fixture to hold the piece.

In the meantime I will try using coolant (I was doing it dry because my coolant pump croaked) and taking a more aggressive cut. I wasn't having a problem with the washers rotating because I really cranked down hard on the nut that was keeping them on the shaft, and cranked it down pretty good to in my vice.

Let's hope I have more luck this time

[gibbsman]

Using a woodruff cutter is old school in my opinion, you were doing it right with the endmill. Carbide is a better way to go with stainless. I don't beleive that a woodruff cutter can compete with the metal removal rate of an endmill. RPM and respectively feedrates are calculated using SFPM X 3.82 / by cutter dia X by chip per tooth. A carbide woodruff cutter would be expensive and to get one in the width you need is probably at least .625" in dia., compared to an endmill around .218" in dia. which I would think would be much cheaper. Even though you would have to take 3 or 4 passes it would still be quicker than using a woodruff cutter, but as I said it is only an opinion trying both ways is the only way to know for sure.

[WilDun]

GiBBSMAN,
You probably are correct, - but to say that carbide is the only way to go ....... ! Old school isn't necessarly bad school, and after a couple of thousand washers, I wonder which method would be cheapest!

FASTURBOVET? SRT MIKE?
I say give both methods a try, and then you'll know for sure, and you will be able to tell us
Very often textbooks and charts, (while good guides for starting points), can sometimes be at odds with reality! - each situation is different.

Please don't try to use high speed steel cutters at the high rotational speeds of the coated carbides though!!

[ViperTX]

I love this..."old school" versus "new school"......geesch whatever that is.......woodruff them...nope that is old school....ah.....broach them....nope that is old school......grind them....nope old school......mill them...nope old school.....I got it.....visualize them done in 3D with lazer reflections...that seems kinda new school....*chuckle*.......Hey, whatever works in your situation is quite acceptable!

[WilDun]

Good simple answer! ( despite all the words).

[Konrad]

this is defiantly not a job for a carbide endmill.......
I can out do the carbide endmill by app. 5 to 1...how can that be "old school"?
Only talking by experience....I can tell, who is coming from the "new" school!

Also, very worry free operation, tool last allot longer then carbide will...why?, because of
the situation we have...not 100% ridged,.... no washer rotation to worry about, which makes it a "much safer" operation, less down time, due to change over of tool etc
eventually, also cheaper on tools, because it will outlast the carbide by app.5 to 1.
Konrad