A knife maker's guide to abrasive grinder belts
Buying abrasives for your belt grinder / linisher can be a confusing endeavour, often leading to trial & error in an effort to find the belts that best suit the task.
To help get you making knives sooner and more efficiently, we have put together a simple guide for the most common belt grinder abrasives used by knife makers, most of which you can find on our website.
While there are countless belt varieties available on the market, we believe this is a good selection that will allow creators to hit the ground running.
Update: We have created an A4 quick reference guide that you can download, print and stick behind your grinder! (click the button below)
Definitions
Before we get into the nitty-gritty, we should first cover a few important terms you will hear surrounding abrasives.
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Friable / friability: Every abrasive grain has the ability to expose fresh (sharp) edges as it breaks down. The rate at which the grit breaks down is called friability. A 'highly friable' belt is able to break down more easily, with less pressure and in softer materials.
- Weights: The 'weight' of an abrasive belt is referring to the thickness of the belt backing (material to which the abrasive is bonded).
Belt Weights
Generally for knife making, you will be using cloth backed belts. Cloth is a durable backing that is able to handle the abuse of metalworking.
The following are a few of the common weights you will come across.
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“Y” Weight – This extremely heavy duty cloth is used for tough grinding applications. It is usually made of Polyester for added strength & tear resistance.
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“X” Weight – This heavy cloth, is recommended for all ordinary machine sanding operations. While a slightly stiffer belt that a "J Weight" belt, X weight belts can be used on small wheels and plunge platens.
- “J” Weight – This flexible, lightweight cloth, is used where more flexibility is needed, such as with contour sanding or when using small radius wheels (Small Wheels, Plunge Platen etc.).
Types of belt grinder abrasives
For 2x72" and 2x48" belt grinders, you will most commonly find belts using 3 types of abrasive - Ceramic, Zirconia and Aluminium Oxide.
While each of these belt types can turn steel and handle material into dust, some are efficient at certain tasks than others.
Choosing the right belt for the application is key to getting the most value out of your abrasives. So what are the pros, cons and correct applications for each type of abrasive?
Ceramic Belts
Ceramic abrasives provide the longest life and fastest cut rate when grinding hard materials such as steel (pre-heat treat and hardened).
These belts are designed to used hard and fast, requiring high belt speed and high pressure in order for the grit to break down efficiently.
These properties make ceramic belts excellent for heavy grinding applications such as profiling and bevelling blades.
While a fresh ceramic belt will remove timber, aluminium and plastics; these materials are not hard enough to fracture the ceramic grain, leading to the belt clogging / glazing quickly.
Most Ceramic belts feature a heavy weight polyester backing for increased strength and tear resistance. This means that they are not suitable for use on the 12mm / 6mm small wheel set or the 6mm plunge platen due to the tight bend radius.
The range of grits available for ceramic belts are usually in the coarse range as ceramic belts tend to glaze quickly in finer grits.
Zirconia Belts
Zirconia Belts lie somewhere in between Ceramic and Aluminium oxide belts. The zirconia grit is more friable than ceramic, but lasts up to 5x longer than aluminium oxide under heavy use.
Zirconia belts are an extremely sharp abrasive making them excellent grinding / sanding timber and other soft materials. When combined with a variable speed grinder, they are brilliant for use on all handle materials such as timber, micarta, antler, G10 and plastics.
Zirconia belts are also an excellent substitute for ceramic belts if the grinder you are using does not have the power to run ceramic belts hard or fast enough to stop them glazing.
Aluminium Oxide belts
Aluminium oxide belts are a low cost belt that is generally available in higher / finer grits.
Aluminium oxide is a highly friable abrasive meaning the grit breaks down effectively at lower speeds or without excessive pressure.
These belts have a relatively short life on hard steels but are great for refining scratches on blade and handle material once the heavy shaping is complete.
By tracking your belt 3-5mm off the edge off the edge of platen, these lighter belts can be used to achieve a nice radius on your plunge line.
These belts are an X weight belt and are suitable for use with our small wheels and plunge platens.
Hopefully this guide was helpful! If you have any questions and would like to know more, feel free to flick us a message on Facebook, email us at team@84engineering.com.au or phone and speak to one of our knowledgable team members on 0448531822.
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