Drilling into lens

jgr

Member
2004-02-05 6:14 am
none
I tried searching for this but didn't find a good answer.

I know I can cut my plastic fresnel lenses with my dremel tool, but can I drill holes into it to secure it to a wooden board? I would drill it with the small drill bits the dremel has.

Will the plastic break or melt at low drill speeds?
 

cbm5

Member
2005-03-14 12:47 am
Arkansas
If you're using the Lumenlab fresnels, I found that they drill pretty easily. I just used a regular variable speed drill and small bit, and let it take its time. Probaly 200 RPM. No speed on a Dremel is "slow" unless you bog it down. But you shouldn't have troubles if you use a light touch, and maybe drizzle some 3-in-1 or motor oil on there.
 
cutting & drilling

But the important difference is the cutting tool, not using a Dremel or some other driver! The best cutting tool for acrylic is one of the thin abrasive disks, because it can't grab the acrylic and break it.

If you use a normal sharp drill bit on thin acrylic, it will grab and shatter it, especially near the edges or corners. A dull drill bit would be better, and a milling tool or abrasive grinding point would be even better. If you have to use a drill bit, then clamp the fresnel between sheets of metal, wood, or lexan, so the drill bit won't be able to yank the acrylic up as the edge grabs it.

Try drilling the scraps with various tools after you cut them, until you find something that works well.

Better yet: just use a clamp to hold it in the frame, instead of drilling holes. Like a piece of aluminum bar stock, screwed to the frame. Or glue it in with RTV.
 

jgr

Member
2004-02-05 6:14 am
none
Thanks for your posts guys. I want to screw it in so it is less susceptible to warping. I'm not placing them horizontally but when i got them from lumenlab they were already a little curved. I tried placing a piece of glass on them and some heavy weights to flatten them but it didn't take care of all the curvature.

Screwing them in will at least ensure that they don't curve unless they melt. I don't really have any split fresnel scrap, just an entire unsplit fresnel from an ohp.

Would using that soldering idron idea not melt too much of the acrylic around the hole? I have about 1/4" of mountable area and wouldn't want to melt anything outside of that. Ill try that on the unsplit fresnel.

If that doesn't work, drilling it with wood supports on the top and bottom will probably work good too, just a little more patience and accuracy needed.

Thanks guys.