Drilling 3/4" C60 carbon steel balls

[milotrain]

I have 108 3/4" carbon steel balls that have a C60 hardness that I need to drill on center. They have a "reflective finish" according to McMaster-Carr which might mean they are chromed (I haven't bought them yet). Assuming they are chromed and I cannot anneal them how much of a PITA is it going to be to drill these guys?

Hole can/should be pretty small but not needle sized. say anywhere from .08" to .25"

Thanks for the help!

 

[steamer]

Sorry Milotrain.....I have no idea what will happen

I know standard drills won't touch it though. I would try a masonry drill and see.

Dave

 

[rake60]

The only way to cut C60 it with a diamond or CBN tool.

Even at that, the diamond or carbon boron nitrate would be like trying to cut it's self.

That's some HARD STUFF!

Rick

 

[GailInNM]

If you don't need the hardness for some other reason, you can buy unhardened semi polished mild steel balls from Tool Supply for about the same price. MUCH easier to machine.
Gail in NM

 

[milotrain]

Thanks so much for the help guys.

Gail do you have a link to the tool supply stock?

 

[GailInNM]

They have an ebay store online. It can be a bit confusing sometimes as their links from the description pages on the balls do not always work.

I have bought from them several times and gotten good service.

Here is a direct link to the 3/4 inch soft polish balls.

http://stores.ebay.com/ToolSupply/3-4-/_i.html?_fsub=12061242&_sid=74456173&_trksid=p4634.c0.m322

Gail in NM

 

[Ken I]

Maybe get your local friendly EDM shop to spark erode it throgh - shouldn't be too pricey if you provide the electrodes.

Ken

 

[milotrain]

Thanks for the link Gail.

I'd think about EDMing it but I've 108 of these to do and that might get expensive. My time and tooling is basically free (hobby, education) but friends with industrial shops have to make a living.

 

[Mainer]

You could try annealing the things, but even annealed they're going to be, to use Guy Lautard's phrase, "Tougher than woodpecker lips."

If you can get by with the soft ones Gail has linked to, that may be the way to go.

 

[Lakc]

Whatever you end up doing, beware that a drill exiting a curved surface will break through on the edges first, and be very prone to snapping. I have learned to slow the feed down considerably if I dont want a broken bit in the hole.

 

[LongRat]

If you have a high speed auxiliary spindle, such as a tool post grinder, you could plunge it into the ball while holding and turning the ball in a collet in the lathe. The axial plunging must be done off centre so the result is a hole that is larger than the cutter being used. Suitable cutters would be fine carbide burs or CBN abrasive tools. Probably not diamond as these generally aren't used with ferrous materials as iron carbide is formed.
This is the method used to produce the holes in CMM inspection stylus balls before the stem is glued in. Those balls are most often ruby, which is somewhat harder than C60. For a metal ball I would definitely say EDM is the easiest method.

 

[Noitoen]

This is from another forum http://youtu.be/d9w-P8QAseg but could do the trick if the hole doesn't have to go deep

 

[MachineTom]

I'd say that a Carbide spade drill should drill that. I've taken out plenty of broken taps with a carbide spade. Which should be as hard as those balls.

If you can choose the hole size .125 would be my choice.