Product Review: Sun-Star Kadomaru Pro Neo 3-Way Corner Cutter

corner rounder - full image

Review by Tina Koyama

The corner rounder I’ve been using is an old Fiskars squeeze punch that is not very comfortable to use. I am also not fond of how the cutting scraps scatter all over the desk and floor. It was time to upgrade to the Sun-Star Kadomaru Neo 3-Way Corner Cutter ($13.75, available in black and white).

I’ve been making myself doodly, abstract coloring books with engineering templates and Field Notes Brand notebooks (see my personal blog for details). I usually use dry colored pencils, but sometimes I get in the mood to use watercolor pencils. Field Notes paper, however, is not the best for wet media, so I decided it was time to make a small coloring book with water-friendly paper. It was an ideal opportunity to test the Sun-Star corner cutter.

A key feature of the Sun-Star Pro Neo is that it offers three corner radii in one compact device – small (3mm), medium (5mm) and large (8mm).

 three sizes

3mm corner

 5mm corner

8mm corner

A lock in back keeps the cutter from cutting paper inadvertently.


I tested it first on a scrap sheet of cover stock. Slide a corner into one of the three marked cutting areas, and press the lever. Requiring little pressure, it’s very easy to use.

cutting corner

I chose the medium-size (5mm) radius for my little book. The cuts are neat and clean.

cover in place

cover corner

The paper I chose for the innards is Canson XL 98-pound mixed media, which has a nice tooth and can hold a light wash. It’s heavier than typical notebook paper, and I comfortably punched two sheets at a time. Three is pushing it.

punched cover and pages

Corner scraps are neatly collected in a compartment at the bottom, which is easy to open and empty into a wastebasket (instead of leaving corners all over the floor or my desk).

opened scrap catcher

There’s nothing like rounded corners to make a little homemade booklet look so much better and more finished! The Sun-Star cutter does the job nicely.

corners on finished book

Incidentally, if you are DIY-ing your own little booklets, I recommend a long-reach stapler. I use a Bostitch PaperPro, which requires very little effort to press and takes standard staples. Its only downside is that it’s difficult to see where the staple will go. I recommend stapling a scrap sheet and use a Sharpie to mark your stapler where the staple went. Then just line up your mark to the location where you want to staple. You will be an instant bookmaker.

DISCLAIMER: Some items included in this review were provided free of charge by JetPens for the purpose of review. Some items in this review include affiliate links. The Well-Appointed Desk is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon. Please see the About page for more details.

tina-koyamaTina Koyama is an urban sketcher in Seattle. Her blog is Fueled by Clouds & Coffee, and you can follow her on Instagram as Miatagrrl.

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3 comments / Add your comment below

  1. Oh my gosh, I have one of those! A 20 year old one from Creative Memories! Gotta fish that out and give it a spot on my desk! Wonder if it can cleanly cut thin paper like TR 52gsm letter sheets??

    1. @Caroline said: “Wonder if it can cleanly cut thin paper like TR 52gsm letter sheets??”

      I’m sure it can, provided the blade is still sharp. Personally I don’t consider Tomoe River 52gsm paper to be super thin, especially compared with the likes of some onionskin and vintage air-mail sheets I’ve handled. Worst case you can always layer the thin sheet with a thicker one then cut the corners together.

      What I was wondering is how thick it can cut. Here is a video I found where the reviewer shows a Sun-Star Kadomaru effortlessly cutting laminate and (separately) a stack of three 120 gsm sheets:

  2. Nice review, thanks.

    The punch reviwed here comes in black and white versions (at my write-time both are sold out at Jetpens). But there is third version from the same manufacturer that seems functionally identical, but different in form factor, and it costs less ($10.00 instead of $13.75). This lower cost version has a sort-of lever on it instead of a button that you need to push on. The lever seems to make more sense to me. Also, the cheaper lever version does not have a lock/unlock knob, which doesn’t really matter to me.

    Does anyone know of any other significant differences between the two punch types other than the lever versus the push-button, and the price difference?

    This page shows the different punch versions side-by-side:

    Here is a link to a video review of the punch with the lever:

    Interestingly, the creator’s comment on the video review mentions this: “Kado” means corner, and “Maru” means round or circle.

    By the way, these punches are one of the very few things from JetPens that I cannot find for significantly less money elsewhere.

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