Ok, no MT-G2 or XHP50 emitters in this SK68 build, although it can easily be done (possible to run a AA sized MT-G2 as done in T10T build MT-G2 Thrunite T10T Ti "Micro Sunbeam" - Flashlight Modding and DIY Parts - BudgetLightForum.com)
Instead, in this build, I am focusing on turning a cheap and budget ZTF light into something actually useful and a daily carry that can be used for most situations.
Here is the end product
I’ve always been interested in ZTF (Zoom to flood) lights, as they have the advantage of a high spotless flood for area work and a focused thrower beam that can be switched on the go.
Unfortunately, ZTF lights tend to lose a lot of light efficiency due to the aspherics, a lot of light is lost to the side of the light (unlike reflectors or TIR, which “collects” the light from the side and throws it out the front), especially when the light is zoomed out, losses of 50% or more is not uncommon
Enter the SK68, one of the most iconic and recognised cheap and budget lights, with its many clones, this light cost probably like 8 dollars?
I happend to have one SK68 lying around, concidentally, this particular SK68 happens to be the very first light I bought years ago when I got into this hobby, so it has a sentimental value as well… it was collecting dust on my table, hence, it was time to “revive” it
First, begin the stripping of anodizing, the light came with cheap anodizing and was peeling, most anodizing can be striped by using drain cleaners (look for sodium hydroxide), it chemically reacts with aluminium to remove the anodizing, it took me 15 minutes (wear rubber gloves, you do NOT want to touch any of the liquid)
The light is then progressively cross sanded with 500, 800, 1000 and 1500 grit sandpaper, followed by polishing with autosol, the result is a mirror finishing of the original light, only some original tool marks were left
SK68s, compared with SK98 (18650 version), has a smaller useful flood, due to the smaller lens and further distance of the lens to the LED, also, due to the smaller lens, small LEDs with high surface brightness must be used, while big LEDs like XML or even XPG will work, the SK68 shines when small LEDs like XPE2 or dedomed XPGs is used
So I set out to improve the available flood and increase its throw slightly, doing some rough sketches and visuals, I figured that I could file off about 2-3mm of the top of the pill so that the sliding head can slide closer to the led, thus improving flood, concidentally, the driver itself took up almost 3mm of space at the bottom, causing the pill to fill up the gap when screwed in tight, thus equalizing the space used for sliding, the result, the LED is now closer to the lens.
I inserted a rubber o-ring on the outside and a glow o-ring in the inside of the head so that when the head is screwed in, makes the head protrude out slightly, increasing its throw slightly (it eats into the flood improvement above, but the net gain is still good), the graphic shows the before and after as well as simulated beam shots
The original AA driver was removed and replaced with a 8 x 7135 105c Guppydrv driver, giving it a total of 3a, the driver does not fit, so I insulated parts of the driver on the underside and taped the driver to the pill with electric tape
Unfortunately, like many SK68s, mine came with a hollow pill, I put thermal cubes into the void and stacked copper discs till it was flush with the “hole”. The thermal cubes are elastic, and hence provide a “springy” bed to press the star against
A noctigon star was cut to fit into the 15mm of space in the pill and press fitted into the pill, pictured here is with a XPE2 dedomed for testing
After testing with the XPE2, while it throws really well, its flood mood is very dim, and the flood beam is VERY weird, with many black zones in the beam, in essence, a very ugly beam.
I reflowed the new osram square 4000k 92 cri to the star, at 3a, it should be able to put out about 500-700 lumens? to prevent artifacts in the beam, I put a sandpaper “gasket” on top of the LED, as well as blacktaping ALL shiny surfaces in the head
To improve throw, the osram was dedomed by slicing it with a sharp knife. I sliced it as close as I could and left it there (no more spare to risk)
As with all my light, I very much prefer forward clicky switches, it was a PITA to get the original reverse clicky switch out, and I wrecked the plastic gasket trying to get the switch out.
Fortunately, the gasket was not needed, the forward clicky will fit with a little filing and rounding of the switch’s square profile, one of the leads at the switch must be insulated as it makes contact with the tail, insulate the spring side of the switch
Finally, the light is ready to go, next to the MT-G2 T10T
I replaced the original tail clip with the tail clip from the T10T, it is much better and does not “rip” your pants like the original clip does
The flood beam is very uniform, MUCH better then the original beam that came with the light (forgot to take before modding)
The zoom pattern is like an “H”, projecting the die pattern of the osram
Also, because the dome was sliced, there is little if no tint shift, resulting in high cri light, both flood and zoom!! Imagine a high cri spot beam
Thanks for reading!!
