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Group buy of logs a few years ago

DPittman

DPittman

Ultra Member
For those who were on the group buy of the steel logs a few years ago that @Jwest7788 and others had arranged...

I'm wondering if anyone got any info on the pieces? I got a 5" piece with a approx1" hole down the centre and in on it was written "4340".
I believe some of the other pieces were 4140.
I have found that I can only turn the stuff with my little lathe only with carbide and very light cuts. It seems to me the 5" hole in the middle stuff seemed harder???
Should I be able to tap any of this stuff with carbon taps or even hss taps?
Is this stuff considered partially annealed?
Another interesting marking on some of the logs was "Quarantine". Any idea what that would mean? (This was pre-covid days).
 
I didn't see any logs marked quarantine - that's interesting. @Alexander what is that?

I have not done much with the 4340 logs myself. anyone?
 
I have a full log of the the 5" 4340 as well. It is definitely harder than the 4140. The log I have is definitely annealed and is very nice to work with but I always use carbide tooling. It turns to a brilliant smooth finish, much nicer than the hot or cold rolled steel I usually work with. I would not try to use a high carbon tap to make a new threads in anything but aluminum as they dull quickly in anything harder and are really only good for chasing existing threads in my experience. Turning a 5" round of tool steel is probably a lot to ask from a mini lathe,
 
"Quarantine"

May have been awaiting evidence that it had been received from approved sources. Met approved specs.

You see that in the aviation field a lot.

Or maybe it failed approval?
 
Johnwa said:
I found I could use HSS if I ran really slow. IIRC about 50 rpm.
Click to expand...
Oh wow was that with both the 4340 and 4140? My little lathe will only get down to 100rpm and it does seem to have enough grunt at that slow. Edit it DOESN'T have enough grunt
 
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Both 4140 and 4340. I was running my Southbend in back gear.
it was a learning experience as I’d never worried about sfm before.
 
Turning 4340 is difficult with HSS as its close to the limit HSS can tolerate - especially things like tapping - which I drop engagement percentage from standard.
 
I found using a positive rake tool in carbide to cut the 4340 quite well, leaving a very good finish. This is on my lighter 12" lathe.
 
I can get a beautiful finish with carbide inserts on the 5 inch stuff but .010" depth is about maximum I can do with my little lathe. Chips roll off blue and if I push too hard they glow red!
20211029_162600.jpg
 
If the material was missing the paperwork I would write a non-conformity report and place it in quarantine. Technically speaking it should have a heat number written on each piece of material and each part that was made from it. The paperwork can be kept separately but must be available. This is industry standard but not something we need to worry about as hobbyists
 
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