# What are these and how are they used?



## gonzo (Feb 27, 2017)

I got several of these when I bought my lathe. They look somewhat like boring bars except the cutting edge does not extend out beyond the diameter.
They remain the source of much mystery to me.
Help me out here.


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## strantor (Feb 27, 2017)

Just a guess, but I'm going to say it's a boring bar that you're supposed to solder/braze a cutter onto it.


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## woodchucker (Feb 27, 2017)

Good guess.


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## ch2co (Feb 27, 2017)

I wasn't aware that Arm & Hammer made machine tool parts at all ??  Perhaps a tool to open one of their industrial products?


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## Wreck™Wreck (Feb 27, 2017)

Looks like a Split Blank, difficult to tell from the photos however.
Like so, carbide rods notched at both ends. Excellent for making tools as they save a lot of grinding time.
https://www.mcmaster.com/#tungsten-carbide-rounds/=16jkd85


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## willthedancer (Feb 28, 2017)

Those are reamers.

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## mcostello (Feb 28, 2017)

"D" reamer.


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## Chiptosser (Feb 28, 2017)

That is single edge cutter.  If you measure over the flat, it will be, half the diameter of the tool.

Notice the clearance ground along the one edge.   That is the cutting edge.   You can grind the face to the shape or clearance angle that your want.  
They are for light cutting.  You can use it in a lathe, or a mill, boring bar or mill.


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## willthedancer (Mar 3, 2017)

D reamers are for low speed precision reaming long holes. Needs a corner radius. A short bore is started at size, and then put the reamer to it. Slow. Lots of oil. The size of the diameter is the size it reams to. 
I'm making one up from O1 drill rod to finish the spindle bore on my new spindle project.

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## John_Dennis (Mar 15, 2017)

I used a similarly shaped carbide tool to drill out a broken tap without damaging the threads of the hole.  I just happened to have a 1/4 carbide rod with the end ground like that. The broken tap was 5/16 so the 1/4 tool left the threads.  I had to resharpen it a couple of times but I salvaged the part.


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