Acrylic drilling help

[vast]

I need some real pointers / tips on drilling my acrylic cover for my CP.  I've probably tried to do it 7 times now and it either results in cracked plastic when drilling the mounting holes, or the holes for the sicks and buttons don't match...

I've got a metal CP and have tried clamping the 2 together and drawing out the holes, sometimes they fit, and then the plastic cracks when drilling the mounting holes.  I'm quite close to giving up on the idea of an overlay 

[SNAAKE]

drill backward. it melts the plexiglass. use a variable drill and go slow.

or just get lexan/lucite tuff. you can treat that as wood. drill however you want. lexan dont crack.

this dude here will cut it to size for you.
http://stores.ebay.com/POP-DISPLAYS/Lexan-Polycarbonate-Clear-/_i.html?_fsub=4957576&_sid=15241991&_trksid=p4634.c0.m322

(this is so old lol)

[Nephasth]

or just get lexan

This. It drills like butter!

And always drill a pilot hole for your larger holes.

[MonMotha]

For thin stuff, I've had pretty good luck using a spade bit to effectively score the edge of the hole from both sides (stop before the bit would start to remove the material from the center area), then popping the cutout piece out.  This is similar to the method used when doing straight cuts where you score and snap, except you can't really bend the entire sheet to snap it.

For thicker stuff, try slow to medium speed and very slow feed with a conventional bit.  A drill press may be useful to keep things straight and control feed speed, but you want to place almost no pressure on the material at all.  I've not tried the "melt the material" technique described above but it might work.  I'm guessing it'll ruin the drill bit, but eh.

And yeah, Lexan is so much easier to work with than acrylic.  It'll scratch a bit worse, but otherwise it will usually hold up better during normal use, too.  Most of the commercial designs I've seen use Lexan for control panel overlays.

[opt2not]

Cleanest way (and practically fool proof) is to drill the desired sized hole into a piece of wood as a template, then drill a pilot hole into your acrylic/lexan/plexi, then use your router and trim bit to widen that hole using the template.

[Turnarcades]

or just get lexan

This. It drills like butter!

And always drill a pilot hole for your larger holes.

We were dubious back in the day about acrylic overlays but seriously, we cut so many now and have never had a single problem with cracking, hand on heart.

We use 2mm Lexan (or Lexan equivalent, and the way we do it is to put the Lexan underneath the panel to be cut (lined up as though it were on top of course), then put a 'sacrifice piece' underneath that, clamping all the pieces together. Drill straight through from the top using good quality spade bits (not saw-edged hole cutters), with the drill set at full speed but applying just medium pressure straight down. There will be a bit of scorching on the wood, but as the sandwiched Lexan cannot vibrate (the main reason for cracking) it will breeze through.

We've been cutting our panels like this for years now and never had a problem. Although technically softer (so less scratch-resistant than perspex), it can flex a lot more so heat generated during drilling will not crack it if done this way. Hole saws are not a good idea as you have to keep them centred anyway, but an adjustable hole saw (with two cutting prongs rather than a saw edge) such as the one we use for trackball holes also cuts through very easily this way.

[Xiaou2]

drill backward. it melts the plexiglass.

Not True.  Ive managed to crack plexi drilling in reverse.   The problem is that the drill isnt removing material when going backwards, and the buildup of material can harden and that cracks the plexi.

 
 The main key to plexi:

1) Use a drill press, or a portable drill guide. Any variance or wobble can cause a crack.

2) Clamp the material.  Any variance or wobble can cause a crack, so all sides much be clamped well. Use rubber / cloth to keep from marring the surface. Dont remove the plexi protective coating till the very end, when all work is done.

3) Drill at maximum speed, BUT lower into the plexi very very very slowly. It should probably take +30 seconds per hole.  The drill will heat the plexi.. melting it, as the blades then clear out the melted material.  If you go too deep too quickly, the plexi is too rigid and can crack easily.

4) As posted, a smaller diameter starter pilot hole will help.  Smaller diameter holes have much less tendency to crack the plexi.   You could even use like 3 passes using 3 different bit sizes if you wanted to.

5) One a hole is finished, immediately fix the carriage bolt through it, if applicable. This again helps the plexi stay flat to the Control panel surface.

6) Use a test scrap piece to practice.

7) Lexan is much easier to cut holes in, however, the surface of lexan will scratch much easier, so when people play on your panel, they will scratch the heck out of it.. most esp if they wear any watches, jewelry, etc.

[Franco B]

Cleanest way (and practically fool proof) is to drill the desired sized hole into a piece of wood as a template, then drill a pilot hole into your acrylic/lexan/plexi, then use your router and trim bit to widen that hole using the template.

^^ this

drill backward. it melts the plexiglass.

Not True.  Ive managed to crack plexi drilling in reverse.   The problem is that the drill isnt removing material when going backwards, and the buildup of material can harden and that cracks the plexi.

 
 The main key to plexi:

1) Use a drill press, or a portable drill guide. Any variance or wobble can cause a crack.

2) Clamp the material.  Any variance or wobble can cause a crack, so all sides much be clamped well. Use rubber / cloth to keep from marring the surface. Dont remove the plexi protective coating till the very end, when all work is done.

Yes. I wouldn't dream of drilling acrylic without a drill press and with a good work holding device. I have a 18mm MDF table top for my drill press with some moveable rubber footed toggle clamps. I can move them so that they clamp either size of the hole in question. You want to get as much clamping pressure on the job as possible to stop it from moving and minimise cracking.

3) Drill at maximum speed, BUT lower into the plexi very very very slowly. It should probably take +30 seconds per hole.  The drill will heat the plexi.. melting it, as the blades then clear out the melted material.  If you go too deep too quickly, the plexi is too rigid and can crack easily.

I have always drilled all of my holes in acrylic at <300RPM. They cut the material nicely without melting and don't leave any kind of nasty melted edge.

4) As posted, a smaller diameter starter pilot hole will help.  Smaller diameter holes have much less tendency to crack the plexi.   You could even use like 3 passes using 3 different bit sizes if you wanted to.

Yes this is a good tip. However, bear in mind that if you are using a forstener or spade bit you need to make sure you leave enough material in the scrap piece below the acrylic for the center point of the next drill.

When drilling smaller holes standard jobber bits you can still crack the acrylic even when using a bench drill and a good work holding device if you try to feed the drill to fast. Acrylic and Polycarbonate (Lexan) are both relatively soft and if you wanted to you could drill through the thicker pieces fairly fast. Its the speed of the drill as it exits the work piece that is the important part. If you feed the drill too fast as it exits the hole it will grab the material and pull the drill through the last couple of millimetres. It is this increase of feed as well as the lead angle on the drill that will crack the material. 

You need to pay attention and keep an eye on when the drill is going to exit the material, obviously with thinner sheets this will be almost instantly. As the drill exits you need to make sure that you are feeding it slowly and at a controlled rate so that the drill isn't allowed to grab and pull its way though. A piece of scrap MDF etc below it is an absolute must as it supports the material around the hole as the drill exits.

90% of the time when cutting large (1/2"+) holes in acrylic I route them to size using a template. To drill the relief hole for the router bit i first drill a ~5mm drill for the pilot hole. I then use a 1/2" metal working slot drill. Slot drills have 0 degree lead on them and nicely cut though the material. Since they have no lead on them they tend not to crack the material as they break through as the whole cutter face breaks though at the same time.

This 1/2" hole allows me to get my roughing bit in. I use a 3/8" flush trim bit but with a 1/2" bearing on it. If I run this round the profile of the hole/profile etc it follows the profile exactly but will leave an even 1/16" of material on for finishing which I then remove with a 1/2" flush trim bit.

6) Use a test scrap piece to practice.

Yes, if you are not used to drilling holes in acrylic etc then you really should practice in some scrap pieces. You don't want to ruin a large expensive piece of material on your first go.

7) Lexan is much easier to cut holes in, however, the surface of lexan will scratch much easier, so when people play on your panel, they will scratch the heck out of it.. most esp if they wear any watches, jewelry, etc.

Yes, Polycarbonate is slightly easier to cut but it will scratch much easier. To be honest acrylic is very easy to cut and its an awesome material to work with.

IMO lexan should never be used for CPOs

[Cade]

I wasted a couple of them before I got the trick.  On thin acrylic the trick is to forget about actually drilling the plastic and instead try and melt it.  Basically just put the bit on the acylic and let it sit there spinning with virtually 0 force.  Eventually the bit will heat up and it will just melt thru the material.  It doesn't take that long honestly but the hole will be perfect.

[vast]

Wow, thanks for all of the replies guys, the only thing that I'm definitely not doing is using a drill press, so I'll grab one and try that.  I've got 2 more pieces on the way over to me at the moment.  This is getting expensive though!

Any advice on getting the holes lined up perfectly with the metal control panel?

I've been clamping the acrylic to the panel and marking out the holes with the CP as a guide, then finding the centre with a ruler and drilling there.   There is always a couple that are off by a couple of mm.  Is there a better way?

[Franco B]

If you have a router and a flush trim bit I would drill a small hole for the router bit and then route them.

The metal CP won't be thick enough for you to run the flush trim bit along so what I do is stick some ~1"x2" pieces of 1/4" acrylic using double sided tape to the metal CP, then use more double sided tape to stick the acrylic sheet to the acrylic pieces.

This will raise the height of the part that you wish to copy which will then allow the bearing to run along it whilst the bit cuts the acrylic.

I actually need to do a similar job tomorrow if you would like me to take some photos.

[vast]

I actually need to do a similar job tomorrow if you would like me to take some photos.

That would be awesome Franco 

[vast]

Followed Franco's advice and routed the holes, came out great 

[MK3FAN]

Lots of good advice here. I made a video a while back...

[ChadTower]

I find that it cracks mostly because when the drill bit gets through it starts to lift the plastic upwards and THAT causes the crack.  What you have to do is make absolutely sure that does not happen.  I usually clamp the plastic between two pieces of wood so that no part of the plastic can be raised during the drilling process.  If I don't have wood pieces to sacrifice I will put three clamps right next to the spot to be drilled.  Anything you can do to prevent that plastic from getting pulled up by the drill bit will likely prevent the cracking.

[monkey puzzle]

Is it possible to use hole saws for the holes? I have a large hole saw for my trackball. Should I risk using this?

[upprc04]

Is it possible to use hole saws for the holes? I have a large hole saw for my trackball. Should I risk using this?

I had great success drilling a small hole and used a router w/ flush trim bit to cut the holes for buttons/joysticks to the same size as the control panel. 

[Turnarcades]

I hate hole saws in general, as to get a clean cut you've got to go in dead level. Adjustable hole saws are good as the cutting tips cut their own path without much resistance, whereas the load on standard hole saws need to be even and at high speed to cut properly. Most of the techniques listed above are all good, though of course we've had lots of experience cutting with space bits by hand in the method mentioned earlier, so will stick with that.

On a similar note, I am toying with the idea of creating an incremental video series detailing one of our builds from start to finish to help kit customers and forum novices, what do you think?

[yotsuya]

Videos sound like a great idea.

I've had nothing but success using a Forstner bit to cut plexi.

[ChadTower]

I've used holesaws.  It does come out a little shredded but you can sand that off so long as you don't walk with the saw.

I have found that rather than trying to cut a perfect hole I have better results cutting a hole that is a little too small.  Then I use a circular sanding bit on a Dremel and sand it to the right size.  That allows you to customize the hole as you need and clean up the edges at the same time.

[Franco B]

I actually need to do a similar job tomorrow if you would like me to take some photos.

That would be awesome Franco 

Followed Franco's advice and routed the holes, came out great 

Apologies for not posting those photos. I did take them whilst working on that job but I completely forgot to post them  Anyway I'm glad to hear it came out ok 

I would like to think I'm pretty good when working with plastics. I may put up a 'how to' thread myself.

As an example, I just finished this for a customer this week. Its a control panel and gun holder for a Sega 2Spicy cabinet. It was all hand routed on a router table and hand polished.

[HaRuMaN]

Damn, dude...   

[ChadTower]

Wow. 

[opt2not]

*snip*

I would like to think I'm pretty good when working with plastics. I may put up a 'how to' thread myself.

^^ this.

 

[Cynicaster]

Wow, that gun holder piece is incredible.. nice work dude.

I busted a few pieces of acrylic when drilling my CPO.  I eventually settled on the following procedure, and it went very smoothly (this process assumes the acrylic and base CP material have already been size matched using a flush-trim bit):

- sandwich together CP, CP layout with "crosshairs" indicating hole locations, and acrylic
- using a small drill bit at high speed, drill a pilot for each hole through the sandwich
- disassemble sandwich, drill holes in CP with hole saw using pilot holes
- use pilot holes in acrylic to make slightly larger holes with a saw-edged hole saw with fine teeth**
- clamp together CP and acrylic so that the edges are nicely aligned, and route out the acrylic holes to size with a flush-trim bit

** These holes only need to be large enough to fit your router's flush trim bit.  I used a cheap-o set of $10 hole saws and it cut through the acrylic like butter, with no "tension" just waiting for something to break.  Very relaxed and stress free.  I think the key is fine teeth, if you went with larger and more spaced out teeth, it might not work.



This process is forgiving because it doesn't require you to be overly precise in any of the steps.  Rather than try to adhere to an exact fixed layout from the get-go, you just match the parts to each other as you go, and the result will always be parts that exactly match each other (if not exactly match your original layout down to the millimeter).