View Full Version : CNC Killflash

05-23-2008, 11:25 PM
I decided to try making a couple of killflash filters for a cheap pair of binoculars just to see how well they work. They work fine. Much cheaper than the $31 that they normally sell for, each. I used black ABS about 0.125" thick and drilled a pattern with my mill using a .035" drill bit on 1 mm hexagonal spacing.





Next is a gyro stabilizer for the binocs. This is just a prototype and will allow me to experiment without worrying about the cost. The binocs were ten bucks.

05-23-2008, 11:42 PM
This may be a stupid question, but can you explain to me what it is doing Evan?

05-23-2008, 11:48 PM
Sorry, I should have said. They prevent any reflections from the objective lens which might give away your location to the enemy, or in my case birds. They also help to protect the lenses. Since these work so well I'm going to make some for my 7 x 50's and maybe even for a camera or two.

05-23-2008, 11:55 PM
A google on the topic will shed some light. Such a set of parallel
pipes basically means you can look out through a small angle
only, or vice versa any one looking in your direction is unlikely to
see the bino optics; one example is a sniper and counter sniper.
The holes mean your bino optics don't glint in the sunlight as any
off axis glare is blocked by the holes in the filter. That is one
reason why sniper rifles have a long hood on the front of the
telescopic sight. xray machines have long used (since the -20s)
such filter in front of the xray film to block off axis scattered
xrays and improve the resolution of the xray. They are called
collimators in this service. "kill flash" can also refer to glint reduction
by objects just outside the desired field of view of the bino such as
reflections off windshields when examining a car park. Optical
collimators are a commonly used device, Evan's device is one way
to make one.

05-24-2008, 10:45 AM

Is there a relationship between material thickness and hole diameter? Is the color important or is it the surface condition, as in non-reflective? What is the spacing of the holes compared to the diameter? I have some "hard core birders" in the family that would appreciate such a device.


05-24-2008, 11:41 AM
The field of view of the binoculars determines the ratio of hole diameter to length. It's simple geometry and can be worked out simply by sketching the hole to scale in a cad program or if you are comfortable with trig it can be calculated. To avoid vignetting of the field of view the cutoff by the edge of the micro-tubes shouldn't exceed 50 percent.

Material should be black and preferably non-reflective when drilled. Black ABS works well and also doesn't overheat as badly as other plastics when drilled. To avoid melting I program the cycle to withdraw a full inch above the work on each hole and use a compressed air jet to cool the bit and work as well as blow the swarf from the bit. If the swarf is melting to the bit slow down the rpm and increase the plunge rate.

Whoa! Live police chase on TV from Vancouver. Some guy driving a semi has gone nuts and is driving at high speed up and down a stretch of hiway making U turns and blowing thorugh busy intersections while weaving all over the road. He only has rims left on the back of the trailer.

Uh oh, he just took out a parked police car. He has about a dozen following him but they can't do squat to stop him.

He just hit a hill and can't make it. He's sliding back down the hill. Just jackknifed across the road and the driver has bailed.

Here come a cop. Hah! No taking any chances on this one, the cop just wiped him out with the cop car at speed. Right up over the windshield. He ain't running any more.

John Stevenson
05-24-2008, 11:54 AM
How much diesel is in the semi ?


05-24-2008, 12:02 PM
? No idea. They'll be showing this one for the next two days on the news. Might even make the international news. At one point he was gaining on a school bus but it looked like somebody radioed the bus and he floored it to stay ahead of the truck, fortunately. The truck came within a gnat's whisker of taking out numerous vehicles in a head on as he was weaving across all four lanes and across the median at times. This is all during morning rush hour.

05-25-2008, 10:01 AM

I guess you get em no matter where you live :eek:

05-25-2008, 10:14 AM
"Minor injuries". The way the cop hit him intentionally I suspect he has at least one broken leg or both. He tried to stand up and immediately fell back down. They had to support him on both sides to take him to the ambulance.

He is obviously more than a few brain cells short of the full complement.

05-25-2008, 11:26 AM
Do you think one of those filters might be useful for a webcam/millcam?


05-25-2008, 11:34 AM
I don't know. What would be the reason for using it in that application?

05-25-2008, 12:37 PM
Well at least with my millcam, it is very sensitive to light and shadows. I was wondering if maybe that filter would make it more stable.

Alistair Hosie
05-25-2008, 01:11 PM
Evan how did you get the extremely accurate spacing with the drilling looks good.Alistair

05-25-2008, 01:52 PM
With my CNC milling machine Alistair.