Re: MOP steel

On 6/22/2025 4:17 AM, Jim Wilkins wrote:

strength of granite is given as up to 45,000 PSI. Single point carbide tipped chisels are recommended to carve it, carbon steel chisels for other types of stone dull in seconds on it. The rock drill rod I turned the jack adapter from is a broken and discarded end with the 3" drill bit still on. 1/2" carbide buttons worn hemispherical do the cutting/ pulverizing, with compressed air removing the dust.
 "Eglin steel can be welded easily" but machinability isn't mentioned. HSS cuts Grade 8.

My two miracle steels (other than various stainless) are 4140 and 1144.
4140 has an edge on corrosion resistance due to some chromium, but not enough to be consider stainless.
1144 has a huge edge due to machinability, but it seems to be only made in hex and round.
4140 is machinable, but tends to work harden unless you take fully engaged cuts with no rubbing.
4140 is somewhat touchy to weld, but with preheat welds nicely.
1144 tends to hot short when welded.  (Crumble or turn granular and crumble if I understand correctly.)
Both are forgeable, but I'd forge 1144 at the lower end of the forging range.  I have forged 1144 at bright red, but not orange heat with good results.
Both are pretty strong in the annealed state and may be used for many tough applications.  I tend towards 4140QT TGP for precision shafting, and if its very low corrosion environment, and I need to turn journals I'll go to 1144.
I tend to use 1144 more than 4140, primarily because its locally available.  I have to order 4140.
Subjectively I would say even in the annealed state 4140 has higher "toughness."
I believe both 4140 (certainly) and 1144 can be heat treated, but I would check the ** ASM Heat Treater's Guide Companion.   1144 may require a little more care due to its tendency to hot short.
If I need an easy mid carbon heat treatable I'd probably pick 1045.
** Unfortunately in the predominate abusive rapist mentality that seems to permeate the tech sector like an incurable virus, the ASM Heat Treater's Guide Companion APP no longer appears to be available through the Google owned Play Store.  First you are forced to create a password to approve payments, and then what you want can not be found.  I have not checked F-Droid, but F-Droid seems have little new to offer as of the last time I checked.
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Bob La Londe
CNC Molds N Stuff
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