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Ball Bearing Knife Questions


Warren Thacker

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Hey guys.  I tried searching for this, but didn't find anything.  A friend gave me a 3" ball bearing and asked if I could make him a knife from it.  I imagine it can be done, but where should I start.  I have a small press to aid in drawing it out, so I won't be hammering for days.  Should I anneal it first?  I'm open to tips, cautionary tales, and advice.

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It seems to help to take it up past critical and let cool before starting to forge.  Glad you have a press, working by hand a 3" bearing would truly take days to flatten by hand!  

 

Once it's forged to shape, normalize the heck out of it.  52100 likes a lot of thermal cycling. That also helps with and drilling or hand sanding you need to do.  

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Brings back memories of a FIF where they gave them 3 inch 52100 balls.   Biggest problem encountered was working material too soon. Participants were working material before interior metal was to temp, and taking too big a bite on initial forming. lots of cracking because of that. 

 

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vlegski beat me to what I was going to say, soak if for longer than you think you'd need to before you work it.  It really needs to be pretty hot all the way through.  Also, small movements (as a percentage) between heats while it is so thick.  

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This is probably obvious, but I had to learn it the hard way so I'll throw it out: 

Don't work it down too far in one direction at a time.  I've never broken down a ball that large, but the couple of times I have used a ball bearing, I learned it is best to try to keep it shaped like a bar with a square cross section until you are within reach of drawing it out into a knife shape.

 

In my case, it was easy to get carried away with the press and go too far in one direction leaving a awkward shape to reduce in the other direction.

Edited by Brian Dougherty
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-Brian

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One more thing:  When you weld a handle on the ball itself, assuming you are going to do that, do it with the ball at least 400 degrees F and slow cool.  This helps keep the weld from popping off a chunk of bearing.  

 

I did that to a 5" bearing I use as a planishing stake. so far it's held up fine!

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Something to be aware of: Not all bearings are 52100. I was in a bearing factory once. When I asked about the steel they were using, he said they commonly used 8 different steels. I don't remember him telling what they were, it has been some years. It wasn't a tour, I was just a tag along driver for a fabricator bidding a job. 

Edited by Matt Walker
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Matt Walker                https://www.youtube.com/@onedamascusmaker/videos

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  • 2 months later...

Warren,

Time flys ….Have you started yet?  Yes on the taking little bites at a time and alternating each bite to make it a bar  as opposed to making a pancake and then turning that on up edge….

 

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