Magnetic Ball Bearing Internal Curved Surface Dent Remover




About: I enjoy everything

I made it at Techshop.

I needed to remove small dents from metal tubes and curved surfaces which are hard to reach.  Items like my horn collection, cans and occasional motorcycle body work.  Well here is one set up of the Magnetic Ball Bearing Internal Curved Surface Dent Remover.  I say one set up, because there are several variations of this to fit the specific requirements.  The ball bearing is placed on the inner surface and is rolled back & forth manually over the dent, using the magnet to keep it intact.  The curve of the ball bearing pushes the dents outward.

Items showed: Top cylindrical item is a rare earth magnet.  Center item is a plastic milk cap; I choose this because of its smooth outer surface. Bottom item is a steel ball bearing. 

Step 1: Set Up

A ball bearing is placed (sometimes dropped) inside the item that has a dent.  I still have my boyhood ball bearings (we use to call them steelies).  I select the largest ball that will fit inside the access hole.  With tapers, I try and go with one size smaller so not to stick in the smaller diameter. I use hard drive magnets with a rag or a cylinder rare earth magnet with plastic milk cap.  Having an item between the dented surfaced and the magnet, allows smooth movement without scratching the surface. The ball bearing is placed on the inner surface and is rolled back & forth manually over the dent.

Step 2: Removal of Dents on Brass Horn

Before and after dent removal, on one of my horns

Step 3: Dent Removal of Aluminum Can

These are not the best of pictures, but here is a before and after of an aluminum can.  This technique works well  (or complements) my snarling tools - see

Please note; there is a correlation between the strength of the magnet and the wall thickness of the dented item and the severity of the dent.  Bottom line is this technique works well but does not get all the dents out. 



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    6 Discussions

    Dave A

    5 years ago on Introduction

    This is smart! At first I thought:"Why?" but than I saw your horn undenting and I've some old horns lying around full of dents. This might become handy, thanks.

    1 reply

    5 years ago on Introduction

    Would't let me reply to your comment but I actually spent about 30 minutes looking and found this site: Hope that helps anyone who needs to buy some.

    1 reply
    Fikjast Scottemauger1

    Reply 5 years ago on Introduction

    The larger one I bought from Detroit ball bearing about 20 years ago. The others are from my boyhood marble collection. I won those in the school yard. I am told by others that you can get ball bearings from the auto salvage yard. I guess they fall out of old trucks. I have not tried this.

    Probably ebay or amazon for new ones

    I wish I could be more helpful.