As I sat at my dad’s workbench I had a sense of déjà vu. It was feeling a lot like a school day. As he lectured me on numbers and equations I had no idea what any of this had to do with polishing knife blades.
Usually a man of few words, he was unusually excited about his impromptu math lecture and I was totally lost.
You don’t have to be a math genius to polish a knife, the lessons I learned from my dad that day have helped me create a consistent and brilliant shine to my knife blades. Read on to learn how and I promise to keep the math to a minimum.
Buffing Knife Blades
Whether you call it buffing or polishing you need to understand this process if you want a professional blade finish.
Buffing is technically one version of polishing and using a buffing wheel will remove small amounts of material from your blade.
Note: If repairing a pitted blade, pits must be removed by grinding before polishing the blade
Prior to doing a finished polish, passes through a grease wheel should first be completed.
Preparing Your Buffing Wheel
Before polishing a blade you need to add buffing compound to your wheel. Buffing compound is fine aluminum oxide with additional polishing agents. It comes in a hardened bar and the bar should be touched against the buffing wheel while it is running. This is called “charging” and will leave some buffing compound on the wheel.
Keep in mind that there are numerous different buffing compound types and the one you use should be formulated for the specific type of steel your blade is comprised of.
How To Buff A Knife Blade
You will need two buffing wheels. Use a course buffing compound on the first wheel. This is referred to as a cut compound and it will provide a light polish to your blade.
The second wheel uses a less course buffing compound referred to as a color compound. This will leave your blade with a bright luster.
Generally speaking, cut compounds are grey while color compounds are white. Be certain to use them in the proper order.
Hold the blade in a vertical position to the wheel. This is because the blade was held horizontal during the grinding process and the scratches will also be running horizontal.
This is called cross buffing and it works beautifully for polishing those scratches away.
What Buffing Wheels To Use
Use loose wheels at a speed of 1750 RPM for the best blade finish. These wheels will also work well on buffing handles making them an excellent all around buffing wheel.
The bright finish they provide is the same as a factory produced blade and the wheels will not create too much blade heat.
Some knife makers will use a hard muslin wheel but these create too much heat and can temper the blade. Unless you have a lot of experience polishing blades I would not recommend going this route.
And polishing a knife is as simple as that. Well almost. Remember that math that confused me as a boy? There is a formula for determining the surface speed of your buffing wheel. This is a bit technical but it’s important to understand. For example, an 8″ wheel running at 1750 RPM with have a higher surface speed than a 6″ wheel at the same RPM. To calculate your buffing wheel surface speed per minute multiply the wheel diameter by pi ( which is 3.1416) and then multiply by the RPM and divide that by 12.
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