Making clean cuts in plastic

[Pasky]

Thought I'd ask this, was gonna PM Xian Xi but his inbox is full, might as well make it public for advice from others and so others will know as well.

Basically I want to know what are some essential tools for making clean cut outs in plastic. I'm rebuilding my CMVS and wanna put a LCD my arduino will interact with so I can set the hard DIPs from outside the case without every having to open it. So that the tarduino will just ground the DIPS based on the settings I select, but I'm terrible at making clean cuts. Same with DB15's and USB ports.

So normally I'd just drill a hole and just use a small file (or large one) to kind of file it into shape but it still doesn't look so great. I've tried a dremel but it'll melt the plastic or the tool will slip and I nick something.

Is there any specialized plastic cutting tools out there for precision cutting thick hard plastic like a specaialized X-acto knife? Any advice is appreciated, thanks.

 

[Craig]

Small laminate router and a straight edge. Clamp the straight edge down and use a cutoff bit in the router.

 

[xsq]

I've tried a dremel but it'll melt the plastic or the tool will slip and I nick something.

hm, I've had ok results using a dremel with the right attachment and a low rotation speed (if the plastic melts you're going too fast). I usually mark with a pencil what to cut out where and take away a litte less material than I need to make the connector (or whatever) fit, then file down the rest, checking with the component every now and then if it will already fit.

Sure, it's never 100% perfect (for that you'd need to have the holes CRC cut or get a punch), but it's decent enough for me.

 

[GohanX]

I'm not an expert, but what I do is mark the cutting area, drill a pilot hole then use a Dremel to make the rough shape I want. I then use some metal files to straighten out the sides and finish with a fine grit wet sanding.

 

[Reclaimer]

I'm not an expert, but what I do is mark the cutting area, drill a pilot hole then use a Dremel to make the rough shape I want. I then use some metal files to straighten out the sides and finish with a fine grit wet sanding.

This. Exactly this.

Getting the bulk of the plastic out with a drill/dremmel/knife is easy. Then file/sand, basically sculpt it down to its final form. Metal files help a ton here. Go slow, start small, test fitting often.

In thin flat plastic, I've also had good results in taping down a straight edge and slowly running an exacto blade over and over again till I'm over 50% through. Then parts will just snap off clean. Sand a bit for nice edges.

 

[ReplicaX]

hm, I've had ok results using a dremel with the right attachment and a low rotation speed (if the plastic melts you're going too fast).

I'm not an expert, but what I do is mark the cutting area, drill a pilot hole then use a Dremel to make the rough shape I want. I then use some metal files to straighten out the sides and finish with a fine grit wet sanding.

These, if you feel you don't have a steady hand or want it perfect use Gohan's method. If you are doing a lot of work I suggest a Dremel press for more control.

 

[Jaelus]

Cover the plastic in masking tape before you cut. You can draw on the tape, it will keep the drill or cutter from slipping, and it protects the surrounding plastic fairly well.

 

[Tyranix95]

Find a guy with a laser cutter.

It's worth it, if you have to have clean cuts.

 

[Pasky]

Cover the plastic in masking tape before you cut. You can draw on the tape, it will keep the drill or cutter from slipping, and it protects the surrounding plastic fairly well.

Why didn't I think of this?!

All this is great advice, thanks everyone.

 

[Xian Xi]

I use blue painters tape. I make all the measurements and draw it on the tape then use a straight edge and cut out parts that need to be cut out then I use a drill bit to cut along the inside of the area leaving about 1-2mm on the inside edge. I then use a router bit on my dremel to get it closer to the drawn outline then finish it off with a diamond file set or an exacto knife for the stubborn corners.

https://instagram.com/p/uOyOnbpYsg/?taken-by=jamma_nation_x

 

[Joneo]

Also, many of the hole shapes you'll likely be cutting already exist in a nicely cut PC card slot bracket somewhere. These make pretty good guides for tracing out the holes on your masking tape prior to cutting.

 

[Pasky]

I use blue painters tape. I make all the measurements and draw it on the tape then use a straight edge and cut out parts that need to be cut out then I use a drill bit to cut along the inside of the area leaving about 1-2mm on the inside edge. I then use a router bit on my dremel to get it closer to the drawn outline then finish it off with a diamond file set or an exacto knife for the stubborn corners.

https://instagram.com/p/uOyOnbpYsg/?taken-by=jamma_nation_x

Sweet. Looks good dude.

Also, many of the hole shapes you'll likely be cutting already exist in a nicely cut PC card slot bracket somewhere. These make pretty good guides for tracing out the holes on your masking tape prior to cutting.

Another brilliant idea, thanks.

 

[DNSDies]

To make the plastic extra smooth, use a fine glass file and then buff it with Jeweler's Rouge and a lint-free cloth.

 

[Xian Xi]

Also, many of the hole shapes you'll likely be cutting already exist in a nicely cut PC card slot bracket somewhere. These make pretty good guides for tracing out the holes on your masking tape prior to cutting.

Exactly, believe it or not, the stencil I use to cut DB15 ports on my Superguns and CMVS units is from a broken AES lower shell. The shell got destroyed in shipping(buyer used literally 4 sheets of newspaper as packing) so I sold him a shell from a non-working AES I had and cut the part that goes around the controller port and use that.

 

[Xian Xi]

To make the plastic extra smooth, use a fine glass file and then buff it with Jeweler's Rouge and a lint-free cloth.

Or in a lot of cases, you can just heat up the plastic with a blow-dryer/heat shrink gun etc.

 

[DNSDies]

Or in a lot of cases, you can just heat up the plastic with a blow-dryer/heat shrink gun etc.

not unless you're using kapton tape to protect the plastic you don't want heated! Errant heat from a heat gun or blow dryer can warp the plastic or even the PCB beneath it.
The glass file and rouge method is only a little more labor intensive, but it's cheaper (and requires less skill) unless you have a fine tip SMD rework heatgun with speed and temp controls and know the melting point of the plastic you want to gloss up.

Also, depending on what kind of plastic you're doing these cuts to (like Acrylic, or clear poly plastics) heat will cause discoloration.

I use jeweler's rouge and a buffing wheel to repair clear plastic with dings and scratches all the time. It works a treat.
Finish it off with a coat of Meguair's #10 and it'll look like new.

 

[ReplicaX]

I use jeweler's rouge and a buffing wheel to repair clear plastic with dings and scratches all the time. It works a treat.
Finish it off with a coat of Meguair's #10 and it'll look like new.

I'll take Novus over jeweler's rouge & meguiars any day.

 

[Atro]

Also, many of the hole shapes you'll likely be cutting already exist in a nicely cut PC card slot bracket somewhere. These make pretty good guides for tracing out the holes on your masking tape prior to cutting.

I use a Soundblaster stencil for the db15s. Helps millions.

 

[GohanX]

I wish I had thought of that when I was adding the DB15 ports to my Atomiswave!

 

[channelmaniac]

+1 for laser cutting.

That's one reason I joined Makerspace.

 

[Voultar]

Here are the two main tools that I use for small/fine plastic casework.

I use a Dremel to take most of the material out, and then when I have it at around 80%, I switch to a fine file to line everything up.

That's how I handle Multi-Out connectors for NESRGB modded systems.

 

[gtdoering]

Lots of patience and a small drill bit and file set. I'm not big on the dremel cause it usually doesn't turn out well for me.