Great find (7/8″ rock drill), but what alloy?

[FulmenParticipant @fulmen]

Came across two rock drills of this type:

22mm inscribed, appr. 3m long. I wonder what steel it could be, something like chrome moly perhaps? I wonder if I can cut it with a band saw or if I need to bring out the cut off disk.

[Michael GilliganParticipant @michaelgilligan61133]

Having seen how tough such items are … I would recommend using the cut-off disk !

MichaelG.

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Edit: __ Here is one I abused earlier:

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[FulmenParticipant @fulmen]

I have a reasonable suspect. And not quite what I thought, I assumed it would be a basic chrome-moly steel:

https://www.alleima.com/en/technical-center/material-datasheets/bar-and-hollow-bar/hollow-drill-steel/sanbar-20/

C-1.0, Si-0.2, Mn-0.3, Cr-1.0, Mo-0.2

This is closer to a tool steel except for the low Mn.

 

Yeah, I’m not wasting a saw blade on that.

[bernard towersParticipant @bernardtowers37738]

Why would you bother with a piece of material that is so specialist / what the h**l would you use it for???

[Thor 🇳🇴Participant @thor]

I have used a piece of rock drill to make a boring bar. It is possible to machine using carbide tools.

Thor

[Michael GilliganParticipant @michaelgilligan61133]

Still a bit thin on metallurgical detail … but this is the best specification document I have found:

https://law.resource.org/pub/in/bis/S08/is.3559.1966.pdf

MichaelG.

[FulmenParticipant @fulmen]

@bernard: I need a few meters of steel bar for a rod mill I’m making. I was planning on using 25mm rebar when I came across these. Cutting it might be a pain but I will give it a try.

Besides I’m always on the lookout for heat treatable steel. I was hoping for something closer to a 41xx steel but it should still be usable. As Thor points out it should make for a decent boring bar.

[DiogenesParticipant @diogenes]

The defining characteristic of steel used in ‘Breaker Points’ will be resistance to repeated impact…

In any case, I wanted to show you this book because I’m sure your local suppliers must have produced something similar in days of yore – old, yes, but the ‘recipes’ will probably allow comparison.. it’s a mine of information.. ..an Ebay job for sure..

 

 

[Michael GilliganParticipant @michaelgilligan61133]

Pardon the topic-drift please … but Diogenes’ post prompted me to find this rather wonderful page:

https://tttg.org.au/index.php/article/Tool_Steels_Survey

MichaelG.

[FulmenParticipant @fulmen]

Good info, keep it coming. Detailed information on most construction and tool steels are available online, but I’m not finding much on these. The data on Sanbar20 suggests a hardening temperature of 1000-1100C which I find very high compared to say O1. But this might prompt me to fix my HT-oven so I can do a few tests.

I have a friend who has an abrasive cutoff saw at work, so that part is covered.

[noel shelleyParticipant @noelshelley55608]

It’s a standard chisel point for use in air or electro/hydraulic tools for breaking stone or concrete. Tough, yes, often reforged when blunt, so the harden able side is less important. When in use they get very hot so any tempering would be lost ? Noel

[FulmenParticipant @fulmen]

These are rock drills from a tunneling project, one of them has a conical point for attaching a drill crown. So they won’t be in direct contact with the work and shouldn’t see enough heat to soften.

[noel shelleyParticipant @noelshelley55608]

Ah, yes ! Missed the point about length, 3m long,now it all makes more sense. Noel.

[Les RileyParticipant @lesriley75593]

As a mining engineer I have used lots of these. When they get worn you can get out the oxy-propane and forge the end to a chisel and use as a crowbar or scaling bar. Every club toolshed needs one!

They don’t bend easily when heaving things about.

[FulmenParticipant @fulmen]

On the bright side they didn’t put up much of a fight against an abrasive wheel, so I shouldn’t have any problems chopping into bits. But yeah, they do make excellent pry bars.

[FulmenParticipant @fulmen]

I got around to cutting them down and the angle grinder was the only real choice. I actually stopped by an old colleague to borrow their shop saw but it was a carbide saw which was absolutely thrashed. So angle grinder it was, and it honestly didn’t take as long as I feared.

I also tried machining them, and it was tough but doable. After dusting off ye olde Reicherter it came out at 38 HRC, so around 1200MPa tensile. I’ll definitely make a new boring bar out of this, with the bore I can even run flood coolant to the tip.

 

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