The Art of Making Ping Pong Ball Diffusers

augusthouse · Post by **augusthouse** » Sat Mar 14, 2009 3:12 pm

The Art of Making Ping Pong Ball Diffusers and Other Related Mysteries.

I'll start this thread with a question or two... ('cause I don't know the answer)

Slicing a ping-pong ball is an art in itself; but how do you make the hole in the top of a ping pong ball to accommodate the barrel of a microscope objective?

Ping pong balls are not very co-operative.

What comes first - the hole or the slice?

Would a rubber grommet assist in securely attaching/detaching the diffuser to/from an MO objective barrel?

Here is a related thread:

http://www.photomacrography1.net/forum/ ... cts+beware

Craig

lauriek · Post by **lauriek** » Sat Mar 14, 2009 4:15 pm

I've contemplated the same problem myself, though I don't have ping-pong balls to hand. I reckon a scalpel would be best to start off with, and the key to getting it to stay in place could be to make the hole _fractionally_ too small in one direction only, so it 'pinches' on. I don't see any rubber grommet in Charles' setup...

augusthouse · Post by **augusthouse** » Sat Mar 14, 2009 5:58 pm

Curved Dissecting/Surgical scissors with a sharp point are providing the desired result. I have an 11cm stainless steel set in my ento kit.

They also provide control of and assist in directing the cut safely and accurately.

Craig

rjlittlefield · Post by **rjlittlefield** » Sat Mar 14, 2009 6:31 pm

I carve mine with a Dremel rotary tool and a small carbide milling bit, then touch up with scissors sometimes.

One useful trick is to leave the hole just a tiny bit undersize, then cut some radial slits that let it expand to spring snugly around the objective.

--Rik

Graham Stabler · Post by **Graham Stabler** » Mon Mar 16, 2009 3:32 am

I found the key was marking it neatly, then you can use a scalpel gently with multiple passes or a Dremel like Rik if you have one. To make a simple hole take some tube with a suitable ID (such as the inner of some sticky tape) and place it on the ball, draw around the ID with a fine pencil.

I also used a soldering iron and considered using a hot wire (I build model aircraft) but it gives off a lot of smoke and I wasn't sure how healthy it was so could not recommend.

Graham

Charles Krebs · Post by **Charles Krebs** » Mon Mar 16, 2009 9:38 am

I use a "compass" circle cutter. Either one like this (CMP-1):
http://www.olfa.com/CircleCuttersList.aspx?C=51
or a readily available compass to which an Exacto blade has been attached. It is not rotated in the normal cutting direction (as you would use for paper), but in the direction that "scores" the plastic. It cuts through pretty quickly.

For smaller holes than possible with the compass cutter, I first make a small hole with an Exacto type blade. Then I use a tapered triangular file. Not in a back and forth filing motion, but rotating it in a circular motion. Gradually I work the taper up to the diameter I want. Makes a perfect smooth hole.

Usually I cut in half along the seam, making a small razor blade incision and then using a small scissors.

Planapo · Post by **Planapo** » Mon Mar 16, 2009 2:45 pm

A helpful technician from my institution has used such a conical drill bit (?, maybe that is not the correct English word for it, in German it's called "Blechschälbohrer"*)
http://www.werkzeugforum.de/Das_Geheimn ... 150.0.html

He used it with an electric drill machine for carving the holes, I had asked him for. It works very nicely with the (somewhat thicker than ping pong ball) hemispheres from some dismantled IKEA christmas illumination and with body caps. If applied with care this method could work with ping pong balls too, I suppose. I have recently bought one of these drill bits myself.

--Betty

*)"These things are not words, they are alphabetical processions. And they are not rare; one can open a German newspaper any time and see them marching majestically across the page. ... Whenever I come across a good one, I stuff it and put it in my museum. In this way I have made quite a valuable collection."
From Twain, M. 1880. The awful German language. In M. Twain, A Tramp Abroad. American Publishing Company, Hartford, Conn.

(Many thanks to Gene,

who kindly recommended to me this hilarious narrative of Mark Twain)

g4lab · Post by **g4lab** » Mon Mar 16, 2009 7:25 pm

Glad you liked it Betty. I remembered it incorrectly as Innocents Abroad another of his collections. I read it in a Mark Twain Reader.

Be careful using a hot wire on a ping-pong ball. They used to be made of nitrocellulose plastic and would burn into nothing very quickly. I believe if the burning is anything like contained they can cause a bit of a POP!

augusthouse · Post by **augusthouse** » Mon Mar 16, 2009 7:49 pm

Ping Pong balls don't like microwave ovens...
http://www.youtube.com/watch?v=s0uX7DIkT3E

g4lab · Post by **g4lab** » Mon Mar 16, 2009 9:50 pm

That is a wonderful video. The composition of the ball probaby absorbs plenty of microwave energy and the whole mass gets its temperature elevated so that its all very near the flash point. When you light one on pavement out of doors they burn with a slight flare and yellow flame and briskly but not like that. And one spot ignites and the flame propagates briskly around it.
But I guess the microwave stuffs it with thermal energy so it all goes off at once as soon as any point reaches ignition temperature.
It does not need atmospheric oxygen to react. Just like dynamite doesn't

DaveW · Post by **DaveW** » Tue Mar 17, 2009 4:50 am

Are ping pong balls still made from nitrocellulose (a form of gun cotton). I remember seeing table tennis matches years ago where a ball just hit had exploded in mid air:-

"By mixing solid nitrocellulose with camphor, John Wesley Hyatt of Albany, New York developed Celluloid, the first commercially successful plastic. The solid material could be heated until it softened and then molded into various shapes. Hyatt formed the Celluloid Manufacturing Company to manufacture and market these products. The earliest uses of this material were mostly as substitutes for natural materials such as tortoiseshell, horn and ivory. Ivory became very scarce at about this time in part because billiards became very popular. Since billiard balls were heretofore made of ivory, a great amount of ivory was needed to make them. Ivory comes from elephant tusks and therefore the supply is limited.

In keeping with the nitrocellulose origin of these earliest plastics, they tended to be highly flammable. Celluloid and Pyroxylin plastics were only slightly less flammable than gunpowder. In fact, on some occasions items made from Celluloid could explode. This was particularly bothersome with billiard balls where the force of impact would sometimes cause the balls to detonate. While this no doubt occasionally made billiards more interesting, it also had undesirable side effects such as personal injury as well as property destruction. Therefore, the explosive characteristics of Celluloid were generally regarded as negative.

Pyroxylin-type plastics began to be replaced by less flammable plastics in the 1920s and 1930s. Nevertheless they did not disappear. Better chemical manufacturing techniques reduced the incidence of detonation in later years. Celluloid plastics are still used in a few applications such as Ping-Pong balls."
DaveW

augusthouse · Post by **augusthouse** » Tue Mar 17, 2009 4:56 am

DaveW wrote:

I remember seeing table tennis matches years ago where a ball just hit had exploded in mid air

Wow! I always attributed that reaction to my wicked backspin

Craig

ChrisR · Post by **ChrisR** » Tue Mar 17, 2009 5:20 am

To have serious fun with ping pong balls you need to nitrate the cellulose. You may find the Nitric Acid fairly hard to buy, these days. I'd tell more but I'd probably get banned.

For smaller holes these hole punches work well
http://i5.ebayimg.com/04/i/000/b2/68/0598_1.JPG
The sets come on two ranges. The smaller one starts 2, 2.5, 3 4 etc millimeters.
They also work on thinnish brass sheet.

Graham Stabler · Post by **Graham Stabler** » Wed Mar 18, 2009 2:08 am

A soldering iron doesn't set them on fire (not modern ones at least) but like I said, no idea about the contents of the smoke.

Charles mentioned using the knife of his Olfa backwards and that reminds me that I think I did exactly the same, it turns the blade into a sort of plane, removing material rather than displacing it. I think you can actually buy knives for cutting plastic sheet based on this principle.

I have a laser cutter at work so that might be one to try.

Graham

AndrewC · Post by **AndrewC** » Wed Mar 18, 2009 6:28 am

Graham Stabler wrote:
I have a laser cutter at work so that might be one to try.

Graham

ROFLMAO - you are a scary man Graham, what do you use for cracking nuts ?

Andrew