Exact procedure for cutting cp: plexiglass, mdf drilling/routing/cutting

[transfan]

Hello,  getting ready to cut my cp and since plexiglass isn't free, I'd like to make sure I am doing it the right way the first time. 

Please let me know if this is correct/optimal or if there's anything I can do to improve success:


1/4" plywood
1/8" Plexi
3/4" MDF

sandwiched together using clamps (or screws?)

Jigsaw to cut to shape, then sand (or route?) edges.

While still sandwiched, put artwork on top of 1/4" plywood and run pilot holes with fine drill bit

then remove artwork and drill 1 1/8" holes through sandwich, going through the 1/4" plywood first.

take the mdf alone and cut a slot along the edge that is offset by the size of the plexiglass

bezel the mdf with a router to hide the extra depth

put it all together

Thank you all so much for your help!

[push2reject]

I would recommend just shaping the MDF first.  Then put the Plexi on top of the MDF and trim it flush with a "flush trim" bit (the one with a bearing on the bottom).  With that much material you'll have a tough time drilling.  I assume you are using the ply to protect the Plexi from shattering.  It is a good idea but is not fool-proof.  You may still shatter Plexi whenever you drill it (especially the thin stuff).  If you layer or sandwich the boards it is a one shot deal.  If you work the MDF first, you'll only be out a sheet of MDF instead of all three layers in the event of a mistake.  You're right Plexi isn't cheap.  I'd get some practice with a router first.  Once you feel confident and understand its limitations you'll find its perfect for working Plexi.  Don't use a jigsaw on layers like that it will bind and drift with that much material.

[transfan]

So you're saying drill the holes in the mdf and then use the holes as a guide with the trim bit in the router?  but you have to drill a pilot hole to fit the bit first, correct?

What size flush trim bit should I get?  lowes.com has 4 different sizes



Any tips for cutting the plexi to a size that is close enough to the mdf to use the router?  I bought a sheet of plexi without having it cut because I was going to do the jigsaw thing

[push2reject]

So you're saying drill the holes in the mdf and then use the holes as a guide with the trim bit in the router? but you have to drill a pilot hole to fit the bit first, correct?

Yep.

What size flush trim bit should I get?  lowes.com has 4 different sizes

Depends on the router.  You want the biggest shaft (1/2 inch) that will fit your router with the smallest diameter blade and bearing.  You can run smaller blades at higher speeds and ½ shafts are more stable.   If you go to Lowes in-store they usually have 2 sizes ¼ and ½ inch with respective shank sizes.

Any tips for cutting the plexi to a size that is close enough to the mdf to use the router?  I bought a sheet of plexi without having it cut because I was going to do the jigsaw thing

Jigsaw is the last thing I would use.  The up and down/reciprocating action will likely crack and shatter the cut.  I would clamp a nice flat board (1x8) to the plexi sheet and rip it with a pattern bit on the router or a straight cut bit with a router bushing.  Run it along the clamped board.  You can also use a circular saw with a backwards rough cut blade installed or plywood blade at a shallow depth.  A table saw work as well.
The router is the go to tool.   I would use it for all cuts and all materials.  Straight cuts on MDF work well using a saw board and a circular saw.  MLCS (http://www.mlcswoodworking.com/) has cheap router blades that are good for beginners.  Lowes can be pricey.
Keep the questions coming and let us know how it works out.

[shan1784]

I just did mine over the past weekend and I had the same concerns as you... Mine turned out perfiect so I'll share my process with you..

I had my plexi sandwiched between my control panel with all the holes already drilled out and another piece of 3/4" mdf. I then used a hole drill bit and used the previously drilled holes as a guide. When I drilled I just let the weight of the drill to provide the pressure.. It ended up melting right through and made perfect holes for the buttons and joysticks.

I then had to cut the shape of the plexi to match the control panel. Again, do not use a jig saw. I've tried this in the past on other non related mame projects and it just made a mess of the plexi. I used a router with a flush trim bit... Mine did not have an arbor to guide it so it was a little tougher trying to eyeball it... So I scored the excess plexi so that it had about a 1/4" overhang on the control panel. I flipped the control panel over, still clamped in the sandwich, unclamped the larger piece of scrap mdf and used a smaller piece (needed more room for the router clearance). Clamped it back together.

The router cut through it like butter... It was very easy and didn't take to long...

Hope this helps...

[BadMouth]

I came across this yesterday and used the info to cut out and drill mounting holes.  This was my first time cutting plexi.
Scoring it didn't work very well at all.  Next time I'll use a saw or router and use a blade that meets the specs in the guide.
Sanding the uneven edge and and drilling went perfect.

http://www.plaskolite.com/products/flat_sheet/optix/

Click on Fabrication Guide.
Lots of good info.

[jimmy2x2x]

This is how I usually do mine (not my video)

[transfan]

went with a router using flush trim bit as suggested.  worked out great.  Thanks everyone!

[MriswitH]

So, from the video it appears he's got some sort of pilot hole already cut out or am I wrong?

From there, just basically work the router with a flush trim bit around till you, in essence, melt/cut the excess away to the hole in the MDF?

I'm quickly approaching my CP build and was very weary of doing the plexi approach due to the fear of breaking such an expensive piece.

Edit: Durp.. I guess I should've just clicked on the video link before posting that.. It takes you to his diary, which basically answered my question. Thanks everyone!

[laggerific]

The router is the go to tool.   I would use it for all cuts and all materials.  Straight cuts on MDF work well using a saw board and a circular saw.  MLCS (http://www.mlcswoodworking.com/) has cheap router blades that are good for beginners.  Lowes can be pricey.
Keep the questions coming and let us know how it works out.

I wasn't too pleased with the MLCS 1/4" bit I got from Amazon...it was a bottom bearing bit, and had serious trouble cleaning up the second side panel (3/4" MDO), and the bottom bearings fell off too quick, and after just doing the length of the monitor it was already looking burnt up.  I decided to splurge and get a Diablo bit from Freud.  I'm basically using the Diablo accessories for all my cuts.  Their carbide plywood blade cut through the 3/4" MDO like butter.  Same for the flush trim bit I upgraded to after the MLCS.  It just looks more solid with the 1/2" blade section, anyway.  The blade was also spotless after going around the entire side panel.

I, too, am starting to plan my CP build, and was considering using the same flush trim bit to do the plexi.  Might need to get a plunge router, though...I don't want to dig into the sides of the hole with an errant shift of the router. 

[push2reject]

I have only used my flush trim bit on plexi at this point.  I use a pattern bit with a 3/4" blade for thick sheet stock right now.  I'll admit my pattern bit from MLCS did develop a bad bearing collar and was converted to a straight cut bit for bushing cuts not long after I got it.  On the other hand the flush trim bit has held up for me nicely.

[justinjstark]

I wasn't too pleased with the MLCS 1/4" bit I got from Amazon...it was a bottom bearing bit, and had serious trouble cleaning up the second side panel (3/4" MDO), and the bottom bearings fell off too quick, and after just doing the length of the monitor it was already looking burnt up.

I have a 1/2" MLCS flush trim bit with 1/4" shank.  I use it a ton and never have problems.  It has cut through mdf and acrylic with ease.  My set did come with an allen wrench to tighten up the bearings but I haven't had a problem with it falling off either.  Strange.  Maybe you got a defective bit!?

[laggerific]

I hope so...I've been super pleased, though, with the Freud trim bit...and their boring bit was up to the task, as well.  I put the holes in the CP today.  Using a straight piece of scrap, I also had a frame to clamp the drill guide down for each hole regardless of location on the panel...and it worked out beautifully...the holes are tight and ready to be used as guides for my flush trim bit on plexi.

The boring bit was a phenomenal success...the cuts came out clean, even without a board underneath to prevent splintering. Once I'm done with the plexi, I need to take some depth out for the Seimitsu screw-ins this CP will be sporting.  Overall, I'm extremely pleased to have not wasted last weeks work making the curves.