How to make a small square notch…

[Curt B]

Hey all,

I’m trying to make a scratch part out of very thin sheet styrene which needs a small (about 2mm) square or slightly rectangular notch out of the sheet.  Ideally, I’d like this notch to be perfectly square (90 degree corners).  I’ve tried to use my Exacto knives, and I also have a small punch set, but I just can’t seem to consistently make these notches perfectly ‘square’. Anyone have any ideas for me?

[Rob de Bie]

Maybe like this? I built small 'ducts' from strip and card. It still lacks putty and repainting.

 

 

Rob

[Curt B]

Rob, Thanks for the reply.  No, what I'm looking for is a way to make the notches in a small thin plastic piece.  Below is the item.  The item is about 20mm wide, and the 2 notches are about 2mm wide.  What I'm looking for is a way to make those notches perfectly 'square', that is, perfect corners of 90 degrees and perfectly perpendicular sides of the notches, and I want to be able to duplicate those notches to make many of these items.  As I wrote in my first post, I haven't found a way to make the notches the exact same size and perfectly square corners, consistently.  You'll note that the notches I made are certainly not square, nor are they of the exact same size.  I did these with a hobby knife.  Close but not good enough for me.  A hobby knife doesn't ensure this, nor do the punches that I have.  I don't know if there exists a tool of some sort that could consistently make notches of this size.  Hoping someone knows of something that might work for me.

 

 

Edited August 14, 2025 by Curt B

[Rob de Bie]

Ah, that's indeed a very different problems than I understood 🙂

 

Maybe make a little jig from plastic strip, that butts against, and slides over the plastic card, and guides your knife cuts?

Rob

[Curt B]

That’s a thought.  Ideally, I was hoping there might exist a cutting tool of some sort, like a hole punch for paper, that could cut notches like that.  I’m sure I’m dreaming that such a tool exists.  

[Rob de Bie]

Nibblers for sheet metal do exist, but I thought that would be total overkill. They are avaible as hand-operated ones., and electric one that are more suitaible for cutting long lengths. But whether you can find one for the size you need?

 

Rob

[Curt B]

7 minutes ago, Rob de Bie said:

Nibblers for sheet metal do exist, but I thought that would be total overkill. They are avaible as hand-operated ones., and electric one that are more suitaible for cutting long lengths. But whether you can find one for the size you need?

 

Rob

Understood.  It’s not THAT big of a deal.  Unless someone else can give me some other idea(s), I may try to create that jig you suggested.  

[Tank]

17 minutes ago, Curt B said:

That’s a thought.  Ideally, I was hoping there might exist a cutting tool of some sort, like a hole punch for paper, that could cut notches like that.  I’m sure I’m dreaming that such a tool exists.  

A square punch set does exist but not sure it will work directly for how you envisioned.

 

https://umm-usa.com/onlinestore/tools-supplies-punches-dies-umma12-square-punch-accessory-p-7109.html?sort=2a

 

I would punch out squares and then glue to plastic to cut out or trance on plastic to cut out/sand to the line.

[ExchefAndy]

I just did a quick search online, maybe using a micro chisel? It would give you the 90 degree cuts you are after.

Type in "micro chisel for hobby" and you should find a multitude of options!

HTH

Andy 

[Tank]

34 minutes ago, ExchefAndy said:

micro chisel

Bought some at Nats but haven’t tried them yet. 
https://umm-usa.com/onlinestore/tools-supplies-cutting-umm12-ultra-micro-chisel-20mm-double-beveled-p-7431.html?sort=2a&keywords=Chisel

[Robert Garelli]

What I would do, start with drawing in lines with a pencil or marker to show how you want it to look. Then either drill or punch inside the lines with a round punch, use an xacto knife to clean up the corners a little.  Then start sanding with a file to the line and refine it as you need to. You should end up with sharp corners. I like using a triangle small file for the corners.

 

I did this in about 5 minutes. 

 

 

Edited August 15, 2025 by Robert Garelli

[Curt B]

Thanks to everyone who has responded...many good ideas here.  I'm going to ponder them all and try to implement each to see which one(s) work best for me...  If anyone is interested, I'll post how it works out!

[Tomcat Trebor]

Do you have a square scribing template, just use that with a sharp needle or sharp blade.

[Curt B]

Hi All,

It turns out that I had the answer all along, though the posts here helped me figure it out. I’ve had the Hasegawa Trytool Template Set 1 in my collection of modeling tools for a long time and never used it. This template is made of thin metal, and It has a variety of sizes of very sharp cornered rectangular shapes. Starting with a sharp pointed awl, I traced the outline of an appropriately sized rectangle, VERY lightly scribing the shape onto a thin plastic sheet, and followed that up with a new Exacto blade.  I’ve found that the key is to make the scribe marks or cuts gently with multiple passes. It works perfectly!

 

Thanks again to all of you who posted!

[Robert Garelli]

18 minutes ago, Curt B said:

Hi All,

It turns out that I had the answer all along, though the posts here helped me figure it out. I’ve had the Hasegawa Trytool Template Set 1 in my collection of modeling tools for a long time and never used it. This template is made of thin metal, and It has a variety of sizes of very sharp cornered rectangular shapes. Starting with a sharp pointed awl, I traced the outline of an appropriately sized rectangle, VERY lightly scribing the shape onto a thin plastic sheet, and followed that up with a new Exacto blade.  I’ve found that the key is to make the scribe marks or cuts gently with multiple passes. It works perfectly!

 

Thanks again to all of you who posted!

 

Glad it all worked out in the end. Good luck with your build. 

[JackMan]

Another suggestion:

https://www.1999.co.jp/eng/10830572

https://www.1999.co.jp/eng/10830571

 

[Curt B]

53 minutes ago, JackMan said:

Another suggestion:

https://www.1999.co.jp/eng/10830572

https://www.1999.co.jp/eng/10830571

 

Now THIS was EXACTLY what I was hoping to find when I started this thread!!!!  I would even consider buying this, but there isn't enough detail in the English to be sure it would do what I want in that if I could be sure that it could do single 1mm wide notches, I'd get it.  It appears that it's only something like $12 US, which is almost nothing...  Thanks for the post!!

[A-10 LOADER]

Use a small square file, that's how I made the chaff/flare bucket holes for my F-16DM.

Steve

 

 

[chukw]

Make it from 4 pieces- the long top, and the smaller lower sections. Cemnt the two outer sections flush with the edges of the long part, and center the middle part carefully between them. 

[Geoff M]

4 hours ago, chukw said:

Make it from 4 pieces- the long top, and the smaller lower sections. Cemnt the two outer sections flush with the edges of the long part, and center the middle part carefully between them. 

That's the ticket!