Installation Blade Tech Talk

I want to talk about something that every installer uses each day whether they are installing window film, paint protection film, vinyl graphics or wrapping a car with vinyl. What I want to talk about are the blades we use in our knives. Commonly referred to as 13 point blades because they are scored in 13 sections to allow the blade to be snapped off, these blades come in many varieties from companies like Olfa, NT Cutter and KDS. We get many questions about the differences in the blades, so I wanted to share a bit of technical data regarding blade construction and what it means for you.

The Hone of the Blade

First, you may have heard of a blade being single-honed or double-honed. What does that mean? Let’s discuss what the “hone” of the blade is and how that affects how the blade functions.

Single Hone

The hone on the blade determines 70 percent of its sharpness. A scalpel has a single hone on both sides of the blade that forms a “V” at the tip. A single hone blade is designed to be sharp, but it is only good at cutting through soft matter. When a single-hone blade encounters something hard, the edge of the blade will tend to roll over or chip (See diagram).

patric1Double Hone

In an effort to correct the chipping and roll over tendency of a single honed blade, and to make the edge more durable, some manufacturers add a second hone (See diagram). This second hone, to be frank, makes the blade duller. But this dullness actually acts to make the blade “last” longer as the edge is stronger with the double hone. Double-honed blades don’t so much cut materials, but push them apart.

So, an installer really needs to determine what is most important. Would you rather sacrifice a degree of blade sharpness for more durability and cutting between blade snaps? Do you want blades that are extremely sharp right out of the box even if that means that you must snap off the blade more often? As is the case with many tools used in our industry, it comes down to the personal preference of each individual installer.

Stainless or Carbon?

Now comes the selection of whether to go with a stainless or carbon blade for your application. Let me begin by saying that typically carbon blades will be harder and more durable than a stainless blade. Many believe that carbon blades are also sharper than stainless blades, but that is typically a result of a carbon blade being able to be honed to a much sharper edge than a stainless blade. The hardness of a carbon blade allows this finer sharper hone to be used while still retaining good durability. So, what blade should you use? That depends completely on application. Let’s take a look at the options.

Window Film Installations

When installing window film, anywhere trimming of the film will be done on the glass, you should ONLY use stainless blades! The added hardness and sharpness of a typical carbon blade will enable the blade to actually cut the top surface of the glass. This cutting of the glass will appear as slight scratches wherever you cut with the blade and leave you with a very angry customer.

All stainless blades should have “stainless” stamped on the blade near the blade retention hole as seen in the picture. If you do not see this stamp, you should assume that the blade is carbon and not use it for any window film application that involves trimming on the glass. Please be careful to check any blades that a pre-installed in a knife that you buy. Many of these knives come with carbon blades installed at the factory and they will need to be changed out before you get started. Not checking the blades in a new knife has led to more than one window needing to be replaced by an unsuspecting installer.

Don’t be the next to make this easy-to-avoid mistake!

Paint Protection Film / Vinyl Graphics / Vehicle Wrap Installations

Because these applications do not require any cutting to be done on the glass, typically carbon blades are used. The reason that using carbon blades for these installations vs. stainless is two-fold. First, the paint protection films and vinyl tend to be thicker than window film, so the sharper edges found on carbon blades make for easier cutting of these materials. Second, the hardness of the carbon blade allows the blades to be much more durable than a stainless counterpart which means much less snapping of the blade.

I think that it should go without saying, but please do not use any of the blades mentioned to cut vinyl or paint protection on the surface of a car. Although some claim to have the skill necessary to do this without cutting or scratching the vehicles paint, I have seen my fair share of damaged paint as a result of this practice and I strongly discourage it.

I hope that this article gives you some basic knowledge of the blades utilized within our industry and why you might choose one over another. As with any job, equipping yourself with the proper tool for the job gives you a head start on a successful outcome.

Click HERE to watch a video with more information about blades.

7 Comments Comment

  • Twitch on July 23, 2014

    Can you advise to the difference in standard Olfa stainless of say 6-7 years ago vs today’s standard Olfa stainless they obviously don’t hold the same edge so did they change the hone ?

  • Patric Fransko on July 23, 2014

    @Twitch…We have asked Olfa directly about this as we have heard from the field that the blades have changed. Olfa claims that nothing has changed about the blades. Our guess is that the softer glass being used by many automotive manufacturers is playing a part, but it also seems that something may have changed as we have heard from too many people to discount it. Sorry that we cannot give a better answer, but we hope that helps.

  • Patrick LeonGuerrero on July 23, 2014

    Hi this is Pat from Pats window tinting Guam great article about the cutting blades yes we use only Olfa stainless on are cutting for window film because we get less mistakes on cut glass we do not want an angry customer thank you Pat.

  • Mike on July 23, 2014

    I hone my blade on my metal cutting guide and get weeks worth of use on one blade. Bin doing this for forty years.

  • Preston on July 24, 2014

    weve always had carbon blades get dull before stainless. and if you know a trick or 2, youll never have a problem cutting the glass with any blade 😉

  • Dick Peterson on July 25, 2014

    The problem with the carbon steel blade is, if you get the blade wet it will rust before you get to use it the next day and you have to throw the whole blade away. The only time I use carbon blades is to cut film off the film handler.

  • Al on August 27, 2014

    Can not wait for your blades they have been a nightmare around here, they just will not cut anymore. Wait to see if I have been buying and fake imitation. Loved the article, been there done that. 🙂

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