Finished I thought

[MachineTom]

So I'm making a Newton Cradle using 2" BB, solid wires and BB pivots. There are 30 2-56 holes to tap, as careful as I can I'm making my way throught the job. I complete the last one without breaking the tap, feeling good as I clean up, there on the side is one more ball untapped drat-it or something like that. lube the tap run it down clearing as usual one more 1/4 turn, back it, crack. Yup busted nice and clean at the surface of the ball nothing to grab onto. No need to attempt removal just drill another hole, interesting drilling a .187 hole in a hardened ball bearing, 5K rpm, carbide $$ drill. Full faceshield, and a chip shield on the work.

Damn I love this hobby.

 

[flatbelter]

Yep, carbide is nice stuff, but did you try heat treating (annealing) the ball bearings first?

Heat em up then bury them in some dry sand.

Will need to be rehardened after machining, and tapping is still iffy...

Sounds like a good project, how did you make out?

FB

 

[MachineTom]

Without a real heat treating oven, annealing would likely ruin the ball, I have O/A setup but without inert atmosphere the ball would discolor any way I tried. The carbide drills are not that dear, maybe $15-20, and it drills quick with carbide. The first attempt was to drill a small hole and fill with low melting temp metal, the metal pulled out with some force applied, so the press in a drilled sleeve was used, so the #43 holes were opened up to 3/16 for the sleeves, they will not come out now. The trick in drilling a sphere is to grind a flat spot the size of the drill, prevents walking on these really hard materials.

 

[mcostello]

$15-20 for a drill bit hurts even from THAT far away!

 

[flatbelter]

I used the carbide drill trick on some rocker arm stud balls once to bore from 3/8" to 7/16". (Ford V-8) It was pretty slick, 16 holes about as fast as you could feed the drill press. Nice wall finish too. M-2 tool steel just wouldn't do it, not for lack of trying at the time...

I was more currious about your tapping methods. Pressing in a softer sleeve is brilliant.

Yea, heat treating would do a number on the finish, but you could probably ball mill polish after final machining. Packing the balls into some iron pipe, or wrapping with stainless foil would help, but not having to heat treat is the easiest solution.

 

[MachineTom]

Yes, what I did is turn a piece of O-1 to press fit into the drilled holes in the balls, then drill the tap drill size hole before pressing into the ball, threading after the press. Worked great, the piece is now complete and the grandkids had great fun starting the balls to clacking and swinging during the Holidays.

Now another piece to hang on the wall, always satisfied when the work is complete and matches or exceeds my expectations.