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Deep Internal Groove - Can anyone recommend a tool?


Apr 26, 2024
Clinton Township, MI

I’m quoting a job that has a EAU of 2,500pcs per year. Material type is C36000 Brass.

We having difficulty locating an insert or boring bar to machine the R.178 internal groove. We were looking at this in a sense of Turning the groove, but cannot locate a tool to make this possible.

Anyone have any ideas besides making a tool to circular interpolate this on the mill? It would be ideal to do this during the turning process.

Thank you in advance!


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Hi Rtstay20:
I'm with Frank on this...you need to make (or have made) a single point boring bar that's no more than 0.9375" diameter so it will fit in the hole and is cut away only from one side to reach in around 0.375". (I'm assuming you MUST access it from the threaded bore and cannot go in from the other end)
That leaves a shank width of about 0.5625" which is a bit scrawny but doable if you don't try to plunge the form in one go.
So I'd make the business end a full radius hook no more than 0.0625" radius (0.125" wide) that's hanging out 0.375"

Like this:
boring bar 20240427.JPG
I'd peck plunge rough with it in three goes and then interpolate the contour to finish.
In 360 brass it should last forever.
Just don't whang it into something and bust it.
Maybe even have it ground as a double ender so you have a backup if one of your guys fucks up an end.


BTW this mockup is modeled to be ground from a 1" diameter solid carbide blank 6" long.
Not much of a hardship for any tool grinding house.
If you really went to town on it, you'd have it plumbed for high pressure air so you don't pack chips while you're using it.
Just have it hole popped for a 3 mm airline, but now making it double ended is more of a problem.
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