I want to cut a piece of plastic peg. The peg will be visible (it is on my laptop stand), so want it to have a smooth finish. I could just use a saw, but the finish will not be good. How should I go about it? I am not sure if a file will be enough to get a proper finish.
I would recommend cutting the peg(s) using a fine toothed saw like this one:
These saws cut very smooth and are made by Xacto. Should be available from most serious hardware stores and craft centers.
Many types of plastics can be sanded with very fine sand paper. You want to look for a product known as "wet or dry" sand paper with a grit number up to 1500 or more. If the cutting operation leaves some saw kerf marks on the stub of the peg you may need to start with a courser paper and then work your way up to the highest numbered grit to get the polish you desire. The Silicon Carbide type wet-dry sandpaper should be available at good hardware stores. Sometimes you can also find this at auto parts stores.
As a follow-up to the advice about using very fine saws and super fine sandpaper, jewelers rouge is often used to do a final polish on plastic to get to a clear finish.
To smooth up the XActo saw cut (a truly excellent tool), you can often flame-polish most thermoplastics, provided you do so carefully. Flame-polished is smoother & shinier than sanded.
Here's the general process:
First, to determine whether this is a thermoplastic or a thermosetting plastic, expose one waste (past the projected cut) edge to high temperature (candle flame, cigarette lighter, etc). If it's thermoplastic, it'll melt. Good sign.
To flame-polish a rod of this material after sawing, carefully expose it to the flame from - say - a stovetop burner. Heat very gently, retract often. The plastic at the cut line will "heal" itself, flowing into the scratches made by the saw and finishing up with a high-gloss surface if done well.
Depending on the type of plastic, and the thickness / dimensions of the cut, a hot knife or a heated wire knife might be what you are looking for.
There are many ways to go about rigging a hot knife, the simplest being to attach an xacto knife blade to a soldering iron. Larger jobs might require a purpose built tool, or at least a much better setup.
Another option is to get the cleanest cut you can, and experiment with a heat gun to soften the cut area. Again, even heating without burning is key, and some plastics are easier to work with than others.
Keep safety in mind, plastic burns giving off very nasty fumes. Most people die on airplanes due to plastic fumes far before any in-plane fires reach them. While you (hopefully) won't scorch your plastic, even heating it should be done with ample ventilation (preferably outdoors).
If you are working with acrylic you should check these technical bulletins for information about how to work with arcylic.
I have successfully used a tablesaw to get a good straight cut then used a variable speed bench jointer to smooth the edge. I was working with 1/4" and 1/8" thick acrylic and resulting parts were all rectangular and more than 1" in each dimension.
If you don't have a jointer you might be able to use a bench mounted router to get a smooth edge but I haven't tried it myself.
I tried other methods for cutting the acrylic but only the table saw could gave me consistently straight cuts. (I tried a band saw, jig saw and the score and snap method)
All the Above are Exellent options to choose from I have also been sometimes successful with using a lazar to mark a straight line “especially when the item is round or circular”. Then I will usually start the cut if possible with a very tight blade on a good or professional quality hacksaw.
I have a Lennox brandon since I was around 16-17 years old, ya I started really early in life and I’m a few months from the dreaded 40; If I make It, but anyway I still have and use the same exact saw and brutally used sometimes and that’s probably putting it lightly.
Then over half of the time I just use the Blade Only! That’s been pretty much all over the best, quickest, and easiest and leaves a decent edge but it’s still a little jagged and unfinished. Not a big deal because like above in the other comments heat works well and Key to a lot of aspects of assaulting a project sometimes.
I use the heating methods as mentioned by the others but I also have a little different way of getting a smooth glossy finished edges product and can also be done in a contour or decorative finish or edging depending on what you choose to use but what I do is heat up a metal object “usually flattened” like scrap metals and very carefully use it like a big butter knife icing a cake! Always Use PPE!!!
There’s no auto parts store for OEM eyeballs and toes and fingers or hands arms and legs or eardrums either so get all OSHE’d up because you only get one or two depending on the body part at risk of loss or whatever else you don’t want.
Hopefully this helps and Your probably well over finish with whatever project It was that you were asking about so it turned out well. or if not you just found a way to not do it and tryout another approach or method for round two. Either way Cake sounds great so see y’all next trip. 🤯