Boring Tools from Ball Bearings

Some time back I used a large, dead, ball bearing to make a bit for a boring bar. Here is the story....


On the right an original ball bearing. The other one was totally rotten, the balls were all actually rusted to a high degree.

On the left, the remains after I sliced out a piece, then removed the ball cage and the balls. Bearing cases are very handy as they are pretty accurately ground and can be used as spacers, riser blocks, packing etc instead of those expensive 1-2-3 blocks.

Slicing was done with a 4.5" angle grinder with a 1mm wide cutoff disk, freehand. These disk are fantastic! They cut fast and cool and waste the minimum of material. I highly recommend that you find yourself some. I was given the 1mm disk and have subsequently worn it a fair bit smaller. I had to travel 130km to the next city to purchase more thin disks as the local hardware stores only have 3mm disks. I got 1.6mm (1/16") disks for a reasonable price and they're just as good.

Last edited February 20 2013 09:52:28.

Closeup of the slice. Didn't get it quite straight across, but it doesn't really matter since the piece is going to be extensively ground to make a cutter anyway. Critical is to keep it cool so don't cut as fast as possible.

Last edited February 20 2013 09:52:28.

The end of the bring bar showing the retainer screw (M3) let into the end of the bar by counter sinking.

There's a gap in the foto series here as I didn' take any fotos of the bit being ground (was about 2 years back after all) and I didn't want to take it out of the boring bar.

Quite simply, the piece of hardened steel from the bearing is ground square (or your preferred shape) by holding it in vicegrips and trimming the edges. Keep it cool though, we don't want it going soft, this is NOT HSS that can run red hot and remain hard.
Having achieved a suitable shape, the end is ground for the intended cutting use. This one is ground for boring (and needs sharpening, spot the little flat on the end) but one can easily grind for single point threading. I prefer sharp pointed tools, some like round nosed. Do what you like that works for you and suites the job at hand.

Last edited February 20 2013 09:52:29.

Rear end of the bit in the bar. I drilled the bar for the 'across flats' size of the bit after grinding, think it was 4mm, then filed the corners in with a small file. You don't have to do this on a bigger bar as you can drill an 'across corners' sized hole and let the sqaure or rectangular bit sit in that. The grub screw will hold it perfectly in a round hole as the corners dig in by themselves. Be careful to get it properly aligned the first time though as you do not want to make groves in the wrong place.

Last edited February 20 2013 09:52:29.

Another top view of the bit. You can just see the flat on the tip where it got blunt the last time I used it.

This bar is a piece of square steel orignally from an ordinary door handle mechanism. I drilled the cross hole and the end hole (a little off center, oops) while it was still all sqaure. I then chucked half of it in the 4 jaw and aligned the end hole on the live center in the tailstock so I could turn the corners off. This gives you a little more leeway in your starting hole size. This one will make it's first cut in an 11mm hole.

For a longer bar I used about 10 inches of 3/8" hot rolled bar left over from building a gate. Same process, drill holes, then round off in the 4 jaw and tailstock center. On the 4jaw page (3rd foto down) you can see this long bar being used to do internal threading. The bit is mounted upside down and runs against the far side of the hole. This gives several advantages when internal threading:

  • you can see what you're doing
  • the topslide setover is 'as usual' for outside threading
  • the infeed is as for external threading
  • the swarf falls away nicely

Last edited February 20 2013 09:52:30.

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Last modified: February 20 2013 07:52:31.