Choosing the right alloy steel - and make a quill

4140 PH is Pre Hardened. It is usually a "medium level harness, around RC 30, so is still readily machinable with carbide and better HSS.
 
The suffix PH, supposedly meaning pre hardened is not at all a familiar term to me, have never seen it in steel catalogs, the term normally means precipitation hardened, a technique in heat treating; the commercial suffix is HT (Heat treated), that is what I always have seen in catalogs, and when I order that material, that is what I specify. It is quite tough, but not so very hard, and machines fairly easily with HSS or carbide, I would suggest that its use is overkill for a small lathe, if I had Stressproof on hand, it would be my choice due to it's machinability and also it's strength.
One suggestion: before embarking on the project, buy a Morse taper reamer to FINISH the bore, it will be money well spent, and available for touch ups if needed.
 
graham-xrf said:
Guys - thanks so much for the replies. Try not to laugh when I admit to being somewhat "YouTube-Trained". I know there is all sorts of potential for messing up doing that, but there are also lots of eye-openers for one like myself.
Dudley Toolwright has two videos where he explores the cutting of 4140 in 3 stages of hardness, two cutting speeds, for both negative and positive rake cutters.


For great entertainment on a property of 4140, WBF777 publishes how to chop up a big chunk of 4x2 with a 4140 tomahawk, then shave hair with it (the tomahawk)! It makes me think the average Gillette could be made of better stuff!

I don't know how hard a quill should be, but my internal reasoning suggests that drill male tapers are plenty hard already, and maybe want to be set into a not-so-hard quill. The friction in there would be better if one of the surfaces was slightly more compliant. I will be going with the temper standard as supplied.

In my internet searches, I came across a new thing to learn about. From the sentence..
"Blaze or consecration hardening of EN24T can accord a case acerbity of 50 HRc or higher."

OK -so I don't yet know what on Earth is "consecration" hardening, and "acerbity" is a new word for me. The mischief in my cartoon mind is right now showing a guy with a blazing torch in one hand, Bible in the other, offering up a prayer before applying the fires of Hell!
Surface flame hardening - right?
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The only thing wrong with the videos is that there is no accurate hardness known for the various samples, the way the heat treatment was done lends little credibility to the purported results, in my view, I doubt that the hardest sample is as hard as represented.
 
The higher carbon and higher alloy steels can become problems from work hardening if you are not quite careful to keep them cutting, not rubbing. Once those metals get work hardened, the job often goes bad. High tensile steel also can move with machining, warping into something unusable as the stresses are relieved. I think something like the 1144 Stressproof that mikey suggested would make more sense all around. Reasonably hard and strong, but also tending to not warp and move as material is removed. 1144 is commonly used for shafting and is very nice to work with.
 
All good suggestions, but in the final analysis you'll have to use what you can (afford to) get. Stressproof, being a LaSalle product is probably not available at a reasonable cost in the U.K. No need to get down in the weeds, use any of the 3 you mentioned and the bronze nut insert.

Next question.
 
benmychree said:
I would suggest that its use is overkill for a small lathe, if I had Stressproof on hand, it would be my choice due to it's machinability and also it's strength.
One suggestion: before embarking on the project, buy a Morse taper reamer to FINISH the bore, it will be money well spent, and available for touch ups if needed.
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John: You are absolutely right about overkill!
I ended up following the MrWhoopee-style line of least resistance, (which means I came across a low-cost 300mm chunk, 30mm diameter in EN24T), and rub into that I count the chromium and nickel content as making it somewhat more corrosion resistant. Only based on convenience and economics, this unreasonable tendency I have to go for overkill wins out!

Re: The suggestion about the Morse taper reamer. Already done Sir! I am looking at the MT2 twin-piece kit right now. I also have the MT3 (came with the MT2 as part of the package deal). I plan to use that one to very gently clean the crud out of the spindle, and peek in there for any dings. I think the lathe was mainly used with chuck for most of it's life, so I don't expect the spindle needs any more than a cleanup and some anti-corrosion (ACF-50).

P.S. The door chime with that fragment of a Strauss waltz just went off. It was the Postie!
Unbelievable! It was only ordered yesterday. It is going to be a bit of a fight to release it from the packaging. Those are big big bent-over staples in the cardboard.

£16.50 ($21.45) and free postage. (Clench fist - punch air a little) Yeah!!

EN24T-Steel Bar.jpg
 
As for cutting the alignment keyway, I'd be looking for a way to mount the part on the carriage of your lathe with an endmill held in a collet. If no collet capability, probably best to find someone with a mill. It's not a critical feature, but we're still (trying to be) machinists.
 
graham-xrf said:
I do agree that the SB quills, though tough, also seem kind of soft, which is why I was asking if anyone knew what they were made of.
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South Bend lathes had two options for their quills - standard and hardened. For standard quills, I wouldn't be surprised that a leaded steel was used, since it machines so nicely. For the hardened variety, some low cost, high carbon alloy was probably used, like 4140.
 
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