Trying to machine Lithium Disilicate

[JayH1119]

So, I've destroyed three Crystallume diamond coated end mills on some Lithium Disilicate I've been tasked with milling. Not only does it wear the coating right off the tool but then it starts eating the tool itself (of course.) I've been working with a high speed spindle and roughing at .001" chipload.

I've only ever seen this stuff machined with small grinding burrs, not with end mills and I'm starting to conclude that there is just no way to cut this stuff, that it must be ground.

Any insights or suggestions would be appreciated. I've also got some Leucite glass-ceramic to try but it's even harder that the LiSi2

Thanks,
Jay

[Dr Pete]

We do this all the time.
Yes your right diamond tool grinding is the way to go.

Not surprising the coating comes off the tool. Depending on the size and what features your trying to put into it.

You can cut it with a diamond blade and coolant on a surface grinder.

You can feature cut it on cnc mill or lathe using the right diamond cutter.

Speed & feeds are real slow compared to regular machining.

Hope this helps,

Dr Pete

[JayH1119]

Thanks Dr Pete,

Do you have any pointers to "the right diamond cutter." ? Or even a diamond grinder I can use in a swiss style collet?

Also, when you say speeds and feeds are real slow, I've been starting at 20k rpm which translates to a feed of about 1000 mm/min at .0254mm chipload. I'm assuming you're talking in the 5k rpm and under range?

Thanks again,
Jay

[Dr Pete]

We buy all our diamond tools either off the shelf or 95% custom made from National Diamond Lab in Los Angeles, CA
Talk with Jerry, his number is 818-240-5770
Fast service and they offer faster delivery on custom items for premium (which we pay gladly to get tools faster)
I have sent him a sketch of a tool in the evening and picked it up the next day.
No connection just a super vendor.

1000mm/min is WAY too fast for what we normally do here (not saying it can't be done)
Our HS spindle only does 10k thou.

We take maximum pass material removal of .005" and usually start at 5"/min then ramp it up or slow it down.

The diamond tools we use are metal bonded usually 100 grit diamond with 3/8 shank. Depending on the finish then we change tool to 220 grit.

Hope this is helpful, good luck on your project.

Dr Pete

[JayH1119]

Thanks for all your help Dr. Pete!