Drilling 5/8 holes in stainless.

[coopec43]

Originally Posted by dlj

Hahaha - your question is pretty vague.

For automotive ball bearings, typically those are manufactured from either SAE 51200 or AISI 440C. when used in bearings, the hardness would typically be about HRC 64 and HRC 60, respectively.

Your second part, is asking "a piece of mild steel".... Now this is much more vague as the term "mild steel", while a common term found, is not a term that has metallurgical significance. It is typically a term used for low alloy carbon steels, of which there are a lot of alloys. Complicating that, there are also different forms and manufacturing techniques.

So for me to give you an answer, I'll define some parameters. Cold-rolled low-carbon steel strip per ASTM A109 can have a hardness range from a maximum of HRB 55 for dead soft material through a minimum of either HRB 90, for specific strip thickness, or minimum of HRB 84 for a different range of strip thicknesses in the "hard" condition...

But clearly, you aren't asking this question to "advance the knowledge of sailors and this sailing forum" are you....

dj

The thread is drilling holes in SS. I suppose that would be of no interest to the majority of sailors but to some of us it is nice to know what we are up against if we want to work on different metals - bronze, brass, iron, steels.....

I once had iron ingots which I planned to cut to length and and use for ballast but I was told by the experts to forget it. I then tried to cut it in my hacksaw and found it impossible.

Maybe I can look at this when I have nothing else to do.

https://www.mem50212.com/MDME/MEMmod.../Hardness.html

[dlj]

Originally Posted by coopec43

The thread is drilling holes in SS. I suppose that would be of no interest to the majority of sailors but to some of us it is nice to know what we are up against if we want to work on different metals - bronze, brass, iron, steels.....

I once had iron ingots which I planned to cut to length and and use for ballast but I was told by the experts to forget it. I then tried to cut it in my hacksaw and found it impossible.

Maybe I can look at this when I have nothing else to do.

https://www.mem50212.com/MDME/MEMmod.../Hardness.html

Might I suggest you start a thread specific to what you are looking for?

I read the link you provided, it's a bit confusing. they are using two different hardness test methods, Brinell and Rockwell. Brinell hardness testing is typically used on cast irons or other alloys with high inhomogenity in the microstructure.

The nomenclature they used talking about the Brinell hardness testing was incorrect. They used the symbol HB - the correct symbol is HBW. Furhtermore, there are multiple ways to run a Brinell hardness test, and there is only one of the many ways of performing the test that allows the simple HBW designation.

The table of values I'm not even sure what they are doing. the top row says Specimen, B scale, C scale. The numbers in each cell for the two scales don't make any sense to me. First of all, if the B scale column was supposed to be Brinell hardness, then the values reported can't be correct. If the B scale column is supposed to be Rockwell B scale, then there should rarely be both columns with numbers in them. The Rockwell B scale is a scale that essentially stops where the Rockwell C scale starts. The only time there might be overlap, and one could possibly have numbers in both columns would be at the high end of B scale, for example a HRB of 99 or 100, might be represented by a Rockwell C value of about a HRC of 20 or 21. If that B scale were representing HBW, then the numbers should be something like 234 HBW to say 243 HBW for that same hardness range. None of the values in the B scale column make sense if it is supposed to be Brinell hardness.

So do yourself a favor, don't waste your time reading that document.

dj

[coopec43]

Originally Posted by dlj

Hahaha - your question is pretty vague.

For automotive ball bearings, typically those are manufactured from either SAE 51200 or AISI 440C. when used in bearings, the hardness would typically be about HRC 64 and HRC 60, respectively.

Your second part, is asking "a piece of mild steel".... Now this is much more vague as the term "mild steel", while a common term found, is not a term that has metallurgical significance. It is typically a term used for low alloy carbon steels, of which there are a lot of alloys. Complicating that, there are also different forms and manufacturing techniques.

So for me to give you an answer, I'll define some parameters. Cold-rolled low-carbon steel strip per ASTM A109 can have a hardness range from a maximum of HRB 55 for dead soft material through a minimum of either HRB 90, for specific strip thickness, or minimum of HRB 84 for a different range of strip thicknesses in the "hard" condition...

But clearly, you aren't asking this question to "advance the knowledge of sailors and this sailing forum" are you....

dj

Thank heavens for google! (This is the sort of information I was hoping for.)



Machinability

What is machinability?

Machinability is the ease with which a metal can be machined. It is represented in percentage relative to a reference metal. A smaller value means the metal is harder to machine. Very difficult-to-machine materials can have a machinability rating of 10-20%, while very easy-to-machine materials can reach 200-400%


https://www.machiningdoctor.com/machinability/