I've had this idea for a while now and finally dug in and got it done. I have the desire to make multi-LED flashlights, but really don't like the whole process of mounting individual reflectors so I figured why not try to make a bit that will cut my own. I've seen a couple of threads in here about guys making their own reflectors, but they were not parabolic.
So I did the math using y = .875x^2 as my formula. I put it into a spread sheet so I could just move the wheels a set amount at a time and went to work on a piece of 7/8 drill rod.
Here's what it looked like after filing and polishing.
At the mill
On to the mill. This was more difficult than the lathe work. I probably only need one flute to cut aluminum, but want two. I debated on how thick to leave the cutting edges and ended up making them too thin on my first attempt. I chucked it up and tried it out. It cut well for a while, then stopped. The cutting edges had rolled over. Back to the lathe to make another. Grr.
My 2nd trip to the mill turned out much better. It's not a great picture, but I have to go to work soon. I'll try to get a better one later.
Here's the test reflector. It has some ridges, but they should polish out. I may be able to hone the edges of the bit too.
I'll post up any results from builds I make in here.
i wonder if after polishing, you fill that with steel balls from bearings and press them, than fill it with slightly different size balls and press it again…what would finish look like…some kind of orange peel perhaps?
Brave attempt, looking forward to the progress. :-) Most chinese reflectors I see are quite irregular, I wonder how much better a 'perfect' paraboloid will be.
Is the finish going to be the bare polished aluminium, or is there going to be a coating?
That’s a nice tool! Why is your finish so rough? If it’s because you’re not using oil, you should at least make the final cut with everything cleaned and oiled. Did you harden the finished tool or dress the edge? Just looks like a lot of work left to do on that surface.
I’m pretty sure that’s what most, if not all, aluminum reflectors are.(?) It’s definitely the easiest!
The finish is actually smoother than it looks. The macro function of my phone really brings out the lines. For instance, the first picture above when the bit is still on the lathe looks like it's a mirror finish by eye, but the picture makes it look like it's kind of rough.
I did harden the finished tool. Cherry red, water quench, blue, water quench again. I didn't have time to hone it. I will try that tonight or tomorrow. I'm tired after work, so probably tomorrow. Come to think of it, I'm working 14hrs tomorrow so we'll see.
I did use lube, but didn't clean everything off before the finish pass. I'll try that next time.
Yes it will be bare polished aluminum unless there is a powder coat that is suitable. I haven't really looked into that, but there are some decent looking chromes out there. Maybe.
That's the most accessible for an individual, but manufacturers use vapor deposition, most likely of aluminum in this application. It might be chromium deposition though, which may explain why when it's rubbed off there's usually a copper colored layer beneath it.
You’d think chrome would make one of the best reflectors but it’s doesn’t. It’s hardness and corrosion resistance makes it superior for holding it’s shine in harsh conditions but aluminum and a few other soft metals are far more reflective.
I may be wrong but I don’t see any advantage depositing aluminum on aluminum since the surface would have to be well-polished before coating anyway. A thin layer of something more corrosion resistant makes more sense. Hardness isn’t important.
Well, maybe not peasy. Remember the average reflector does what, about 15% loss and that’s a plated one. Polishing will leave tons of microscopic scratches. Check it with a 15x loop after and see. I imagine it will loose 20-25%. I’m not knocking what you are doing. It is an awesome test and one that I haven’t seen hardly anyone willing to try. I applaude your efforts and look forward to the result.
I wouldn't think it would be superior, except for those people that can't keep their fingers out of their reflectors, although aluminum coatings can have a polymer coating (used in automotive reflectors) that reduces efficiency by ~5-10%, but it's still better than chromium. The advantage should be a more uniform surface. You can polish an aluminum reflector, but you can't polish away the imperfections in the material. Some more expensive billet aluminum is formed under a vacuum to improve its quality, but there are still imperfections that occasionally make it unsuitable for an engine, not to mention a reflector. There's a whole lot about this that I don't know though. Everytime I start looking into this, I also look at economical rigs and lose interest when concluding that there's no budget way of doing this and there doesn't even seem to be shops that will do small orders.
I have tried to make my own reflectors before. The reflector finish turned out good but trying to get all the proper angles and curves in the reflector is way over my head. With each led type requires a different shaped reflector. The one I made turned out to be quite floody, it did have a large hot spot that was only slightly brighter than the spill. Would have made a great close up light I guess. I kind of like to have both, a decent hotspot that will throw a little and decent spill to light up the surrounding area. Looking forward to seeing some beam shots. Great job with making the cutter. Excellent work.
