Thread: Looking for a 0.444" diam ball bearing

http://www.precisionballs.com/index.php

Bal-tec. First one Googled. A $20.00 minimum order and they have all kinds of materials including carbide.

I saw 440 SS ones for $3.59 and they have 9 in stock.
Bal-tec Inc., Ball Inventory

Pete

Thanks for the leads guys.

I tried my small rotary table on a bit of mild steel.



Bit of wet and dry and . . . . .
final diameter is 11.58 mm


Not perfect but remember the hardness of wood on a tree varies by +/- 20% so the bias from the ball will be a minor component of the final uncertaintie.

Now to do the same thing to a bolt.

Hi Bob,
Are you sure you have half a sphere and not half an AFL football?
I'd thought about this earlier but thought as you said it wouldnt matter much. But you're going to be using the radius as the depth. If you have a football a radius could be to shallow or to deep.

Of course it you might not be far enough out for it to make much difference.

Stuart

Yeah, it does look a bit footballish but that could be because the shape is turned as follows.

I turned the end of the rod down to to 11.62 mm in diam for a couple of mm longer than half the diam.
The slanted shoulder of the shank is just due to the shape of the cutting tool. I will change that to a 90º cutting tool end for the real thing.
Then I lined up the rotary table and adjusted the cross feed and cutting tool position so when I rotated it through 180º it just kissed both sides of the 11.62 mm diam shank.
Then I moved the saddle in by small increments and rotated the rotary table back at forth by 90º until it was cutting during the whole 90º of rotation.

It would be useful if the shoulder was exactly one radius from the end of the rod as the force meter would then register a jump to tell me it was exactly half way in but the testing machine has a precision (micron level) position read out so I just need to get it to register the force as a function of distance and I'll just take the force reading at 0.222" after the first position it registers any force (ie first kiss).

If you are interested to see where I got to with this have a look here.