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How to create round corners and
convex surfaces with a file

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Image of a DIYer cross filing a piece of metal This process is similar in many ways to cross filing, but without the sideways movement.
A flat file which is used for rounding corners on a work piece You will need a file with a flat face. Hand, flat and half round files will work best.

Creating a curved surface

Image of a vice which should be used to secure the work piece in place

Step 1 – Prepare workpiece

Clamp the object you are going to be filing into a vice so that it is secure and doesn’t wobble around. Don’t forget to use a filing block!

Image to illustrate how to hold a file properly

Step 2 – Grip file securely at both ends

Use your dominant hand to hold the handle of the file, with your thumb aiming for the file’s point. Grip the point of the file between the thumb and forefinger of your non-dominant hand.

Image to show a DIYer preparing to file a curved surface by tilting the point of the file upwards towards the ceiling

Step 3 – Tilt point upwards

Before you start to file, tilt the point of the file upwards and push the handle downwards. This will set the file up so that you can start to create the round edge as soon as the file starts moving.

Image to show how a push stroke should be conducted when filing a curved surface

Step 4 – Push stroke

Applying light pressure, push the file forwards. As you do so, push the point of the file downwards and lift the handle of the file upwards.

Wonkee Donkee advises that you are careful to keep the face of the file in contact with the work piece
Image of a convex surface which has been created from a flat surface using a metal file This rocking motion will create a curve on the surface you’re filing.
Image showing a DIYer replacing their flat file in the position where they originally started their push stroke while filing a convex surface

Step 5 – Draw stroke

Return the file back to its starting position, but lift it away from the workpiece to do it.

Repeat the process

Step 6 – Repeat

Repeat this process, moving along the workpiece until you have rounded the entire edge or surface that you want to add a curve to.

Corners or convex surfaces?

Image of a DIYer using a flat file to round off the corner of a metal work piece The technique for creating rounded corners and convex surfaces is almost identical, but for two key differences.
Image showing the shape of the stroke for filing a work piece with a rounded edge To create a smooth corner, the file needs to start flat against the top of the workpiece. On a convex surface, you could choose how steep the start of your curve would be.
Image to show that a DIYer has to tilt their file much more quickly when they are rounding corners than they do when they are filing a convex surface When rounding a corner, you will need to tilt the file relatively quickly as you are rounding off a very small area. If you were working on a convex surface, you would be tilting the file much more slowly.

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