Drilling New Lexan to Fit Existing Holes?

[Jamesbeat]

I'm so mad at myself.
I messed up my Lexan cpo while trying to paint it, and I think my only option is to start over.

Here's what happened if you want a laugh:

Drilled Lexan and wood together.
Painted back side of lexan black with Krylon Fusion spray paint.
Ran out of Krylon Fusion, store had none left, so bought Krylon Maxx Cover.
Watched in horror as the new paint made the old paint wrinkle spectacularly.
Tried to strip paint off with oven cleaner (I thought paint stripper would damage the plastic)
Repainted the Lexan.
Removed protective plastic film to discover that the oven cleaner had made the Lexan go 'milky' in some areas.
Tried to sand off the milky areas, which was only partially successful, and scratched up the now unprotected top surface.

I could probably rescue it and polish out the scratches, but I've wasted so much time on this now that it's just not worth it any more.

The problem is, if I start again with a new piece, I don't know how to get to get the holes lined up perfectly with the holes that are already in the wood.

I don't think that clamping the Lexan to the wood and drilling through the holes will be accurate enough. I experimented, and if I don't get the drill exactly perpendicular  I could end up being as much as 1/8" off.
I have a drill press, but my control panel is already built, and thus won't fit into the drill press.

I know I can't be the first person facing this problem, as I'm sure there are plenty of people who have cracked a Plexiglas cpo, but a search didn't turn up anything useful.

Any ideas?

[Slippyblade]

Being an 1/8" off shouldn't be a big deal.  Your button bezels will cover that.

[Jamesbeat]

But if the hole is 1/8" off from where it should be, the button won't be in the right place.
Or do you mean that I could 'egg out' the hole until the button is in the right place, and the button bezel will disguise it?

I feel like I must be missing something obvious.
The problem is finding the centers of the holes.
Maybe I could use the existing overlay to somehow line up a new printed button template?
I still have a copy of the exact template that I used to drill the original holes.

[Slippyblade]

I guess I'm confused.  Why do you need to know where the center is?  What kind of bit are you using to drill the lexan?

[Jamesbeat]

I need to know where the center of each hole is so that I can get the drill bit started in the right place.
Clamping the Lexan to the wood and using the existing holes in the wood to line up the drill bit won't be accurate enough. I tried it, and at this diameter, it just not accurate enough using a hand held drill.

I'm using a spade bit, but this would apply to any drill bit.

[Slippyblade]

A spade bit with lexan?  Wow - I'd expect that to explode the plastic.

I use a hole saw.  If you clamped the lexan to the wood then the CP would align a hole saw.  Sorry.

[Jamesbeat]

Yeah, Lexan is a completely different beast to plexi.
It cuts almost like wood, and it's practically impossible to crack.
That's why I chose to use it
The downside is that it's a bit more expensive and is somewhat easier to scratch.

[yamatetsu]

I need to know where the center of each hole is so that I can get the drill bit started in the right place.

Simple solution : Clamp the plexi to the wood. Let's pretend your holes are 1 inch in diameter. Take two toothpicks and cut them to 1 inch. Put one horizontally, the other one vertically into the hole. The intersection is the mid-point of the hole.

 

[Jamesbeat]

That's not a bad idea!
Maybe a mist of spray paint through the hole with the toothpicks in place would give me 'crosshairs' to aim for.
I'll give it a try, thanks.

[Maphreal]

The easiest way I've found is using a router with a flush trim bit.

Clamp the lexan to the wood, drill a starter hole big enough for your bit in each hole, and the flush trim bit will cut it to match your wood holes perfectly.

You can only mess up if you do what my drunk buddy did - after routing out a hole, he picked up the router from one side while the bit was against the edge of the hole. The router was still spooling down and cut into the plexi at an angle due to being picked up lop-sided. It's a pretty easy mistake to avoid, though.

[aldub516]

i personally do not see whats so hard about re-drilling these holes? ive used scroll saws, dremels with a drill bit..

im not sure why you cant just lay the plexi right over the wood, drill holes through the lexan and the wood holes, and just route/dremel/sand down the holes to the diameter? or even just use a hole saw that matches the hole size? If you have all the holes in the wood already, i feel like theres 100 different easy ways to make new lexan holes to match. From what i gather, youd be using a 1 1/8th inch drill bit to re-cut the lexan, and are afraid you wont be able to hit the EXACT center of each hole? In that case, drill a hole smaller than the wood hole, and use any number of tools to file it down to a clean circle matching the wood.

My personal route would be:
clamp down lexan over wood with holes
drill a hole right in the middle of the lexan over a wood hole, big enough to fit a router or sanding dremel into..then stick said router or dremel in the hole and just run it flush with the diameter of the wood hole.. lexan in my experience is extremely rugged. I can almost say i have to try to mess up lexan when cutting stuff... dremels melts right through it, table saws, basically anything..

also, kudos for the ridiculous attempt at saving that first piece of lexan lol. I dont think this should be very hard to do at all.. infact, rather easy.

[Jamesbeat]

Yes, drilling smaller holes and then enlarging them definitely seems to be the way to go about this, as it will negate the problem of locating the exact center of the holes.

Thanks guys, I think I've got this.

[Slippyblade]

We expect updates.  :p

[Jamesbeat]

I have a bit for my dremel that I was going to use (I don't have a flush trim router bit) but when I tried it, it was extremely difficult to control.

I ended up printing out my templates again, and taping them to the underside of my old cpo.

I lined up the templates exactly under the holes, and that gave me the centers I needed. I then clamped the old cpo over the new Lexan, center punched the holes, and drilled them.

It turned out almost perfectly. There is one hole that needed a tiny bit of adjustment with the dremel, but it was a lot better than trying to hog out 16 holes!

The flush trim bit idea was a good one, and probably would have been easier, but I got the job done.

[rackoon]

I have had this happen a few times. I took a hole saw and took out the arbor bit. Then I sandwiched the plexi between control panel and another piece of wood and drill lightly until hole is deep enough to guide its self