On Thursday, February 23, 2012 04:54:40 PM Kent A. Reed did opine: > On 2/22/2012 9:35 PM, gene heskett wrote: > > On Wednesday, February 22, 2012 09:14:52 PM R.L. Wurdack did opine: > >> Whatever you use, beware of reflections from the sides of the slots > >> themselves. > > > > Precisely my concern. The front& rear faces of the disk are > > basically a never mind. Its the walls of the slots I am concerned > > with. > > > >> i.e. The surface of the disk may not be the only reflection > >> problem. Will lampblack with a coat of clear flat Krylon work, or > >> just flat black Krylon.? > > > > Lampblack would be fine IF one could find a binder as effective as the > > krylon that wasn't glossy at low incident angles. A case where thin > > is good, but I expect trying to mill the outside 1/3" of it down to > > the point where knife edge diffraction was the major effect, would be > > pretty frustrating. Hence the search for something that would leave > > a truly non- glossy surface. I, after thinking about it, may just > > clean it up with Tarnex to dull& degrease the surface, and after > > much rinsing, try the vinegar dip and ammonia fumes route. After > > adjusting a few more params in the gcode, just made another, > > considerably neater cut one I am quite a bit happier with, if I can > > get it suitable blackened inside the slots. Low res .jpg attached > > > > Actually Dick, this is a case where a roughing bit might have been an > > advantage. :-) But I don't know as I've ever seen a 1/16" diameter > > rougher. That doesn't mean they don't exist, just that I never > > thought of it till a couple minutes ago. > > > > Hindsight, always 20/05 or better you know. :) > > Gene: > > Back when Jimmy Carter was President, I was engaged in some high-end > optical physics work that included measuring the specular and diffuse > reflectance of a large number of materials as a function of wavelength > and of angle of incidence. I could tell you what it was for but then I'd > have to...well, you know the saying. > > I never found anything better than lampblack smoked right onto the test > coupon. It became our reference material. Of course, it lasted only as > long as we didn't touch it. > > One technique that can help mitigate the reflectance from the sides of > the slots is to collimate the light source and use baffles before and > after. > > Simple pencil-and-paper raytracings of prospective geometries can reveal > a lot. So can a test rig with a scope. > > Good luck. > > Regards, > Kent > I've been screwing around with it a bit this afternoon, first giving a good scrubbing with lava bar soap which has pumice in it, dried, then rinsed & swirled for a few minutes in acetone, dried, then dipped in vinegar & hung over a half inch of ammonia in a capped container. What I seem to be getting is a very mottled almost black with red splotches, and the vinegar held in the slots by meniscus action is slowly dripping a blue tint into the ammonia, and on the re-rinse in the vinegar, slowly turning it blue. And it doesn't appear the edges of the slots, freshly cut without anything but an air sweep on the tool, no coolant/lube to contaminate the cut surface, aren't taking the color very well. I am not having great luck getting the brass to wet with the vinegar, even after I wasted an old brush in our electric toothbrush & worked it over again under the vinegar just now.
When the missus and the car get back, she's knitting a baby blanket or something for a friend, on a knitting loom we bought but haven't brought home yet & might get finished today if she has what it takes, copd being what it is, and I am getting tired of not having wheels so the check may be wrote for a fresher pickup yet, I've been stranded without wheels most of the week so far and haven't had a chance to go run down some liver of sulfur when a real pharmacist is behind the counter. Or even some of the Brass Black at wallies. Tonight, or I write a check. Hell, I can't even get to Advance Auto & talk to the real man about ordering a $2100 reman engine for my GMC! I am getting a bit frustrated as can be read here. Cheers, Gene -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) My web page: <http://coyoteden.dyndns-free.com:85/gene> "But Huey, you PROMISED!" "Tell 'em I lied." ------------------------------------------------------------------------------ Virtualization & Cloud Management Using Capacity Planning Cloud computing makes use of virtualization - but cloud computing also focuses on allowing computing to be delivered as a service. http://www.accelacomm.com/jaw/sfnl/114/51521223/ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
