# Drilling spheres



## mklotz (Nov 23, 2009)

A friend of mine asked me to drill some holes in some wooden balls for him. While this has nothing to do with model engineering, the fixture I used to accomplish this might be of interest (and future utility) to some of you.

The balls are 3" diameter - too large to hold securely in any of my lathe chucks, not to mention the fact that the chuck jaws, even padded, might make dents in the wood.

I took two pieces of 3/4" plywood and, with a hole saw, drilled a 2" hole in the center of each. Two additional holes were drilled to match the spacing between the T-slots on my mill.

The first photo shows how the ball was sandwiched between the two wooden plates on the mill table. Studs and nuts draw the top plate down on the ball. By reefing on the nuts, I got a pretty good death grip on the rather smooth balls.







This photo shows the underside with the studs and the trapped ball...






And here is the finished product...






The balls were drilled with a 3/4" Forstner bit to create a nice, smooth hole.


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## Artie (Nov 23, 2009)

Using the head Marv.... the boxes of bandaids next to the mill? Do you have a recuring problem with claret leakage? 8)

Cheers

Artie


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## bearcar1 (Nov 23, 2009)

At lest he moved up from the 'clear; ones to "ouchless" Rof}

BC1
Jim


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## zeeprogrammer (Nov 23, 2009)

Very handy tip Marv. Thanks.

What is 'reefing'?

How did you center the ball under the press?

The top board looks like the hole is beveled (chamfered?). Did you do the same for the edges against the ball? Any special consideration of angle?

And yes, I'm a little worried about having all those band-aids around too. Tell me you've recycled them to hold other goodies. (Actually...hard to tell in the photo...but it looks like they are.)


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## mklotz (Nov 23, 2009)

Centering the ball...

Touch off with an endmill on the eyeballed top of the sphere. Lower the endmill by twenty thou or so and mill a flat on the top of the sphere. This results in a very small circular flat. Eyeball the center of this circle (this is wood after all) and make a pencil mark. With pointy rod in chuck, futz around until point is on pencil mark. Voila, centered good enough for wood work. (Can you tell I have no respect for the medium?)

Reefing = slang for really torquing down a nut. It sounds like the origin might be nautical but I'm too lazy to look it up. BTW, it has nothing to do with the evil weed.

The holes in the boards are not beveled. It might be worth doing but, beveled or not, you're only going to have line contact on the sphere - hence the reefing.

Yes, despite my name, the Band-Aid boxes are there not for first aid, but because they're pretty much a perfect fit in the mill table coolant gutter and they're the right size to hold parallels upright.


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## zeeprogrammer (Nov 23, 2009)

mklotz  said:
			
		

> futz Voila Reefing


faffing (or phaffing) , Jabberwocky, and Scheiße...

pencil mark!

Man it's tough getting this jargon down.

Holders for parallels may be true...but having that many band-aid boxes still in service implies...

I like the fact that these tools can be used to do so many things.


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## mklotz (Nov 24, 2009)

You forgot 'aliquot'.

When you're more grown-up, we'll teach you about:

BFH - the ultimate tool
RCH - the ultimate measurement
RCI - my personal contribution, the ultimate confusion

Isn't English a wonderful language? 

My favorite quote on the subject...

The problem with defending the purity of the English language is that
English is about as pure as a cribhouse whore. We don't just borrow
words; on occasion, English has pursued other languages down alleyways
to beat them unconscious and rifle their pockets for new vocabulary.


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## Captain Jerry (Nov 24, 2009)

Just a thought about centering (if it ever comes up again. If you mount the wood plates on the mill table and drill through the top plate and into the bottom plate with a large forstner, then the balls will be perfectly centered as long as you dont move the bottom plate. That might mean separate bolts for the top and bottom so you can lift the top without moving the bottom. 

Jerry


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## zeeprogrammer (Nov 24, 2009)

mklotz  said:
			
		

> You forgot 'aliquot'.



I did! There was one other you used recently...but I don't have the right memory for it. :big:


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## ChooChooMike (Nov 24, 2009)

Those metal band-aid boxes/tins made a bit of a comeback  A couple of years ago I found a whole shelf full of those metal boxes in the medical aisle ! Think it's a great marketing tool


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