Centuar Ultra-t-shift sstem

On Sat, 22 May 2021 12:57:06 -0400, Frank Krygowski
wrote:

On 5/22/2021 2:06 AM, Jeff Liebermann wrote:
On Sat, 22 May 2021 10:56:25 +0700, John B.
wrote:

On Fri, 21 May 2021 19:17:06 -0700, Jeff Liebermann
wrote:

Nice, but a little big for a bicycle. I've stripped a few bits,
usually from driving at an angle. I've tried hardening some bits,
which helps.
"Experiment CRASH TEST hardening bit for screwdriver"
https://www.youtube.com/watch?v=Y7RSfVqbjSo (3:00)

Quite simply that guy doesn't know what he is doing, at least as shown
in the film. The quenching in carbon is probably a rather futile
attempt at case hardening and had he submerged the bit in carbon dust
and then heated the whole mess to a red heat and held it there for a
period and then quenched the bit he would have had far more success.
As for his quenching in liquids he doesn't seem to get the bit
anywhere near hardening temperature, i.e. red heat.

+1

He doesn't get it quite right, but I like the method and the result.
However, as you note, he made many mistakes.

Quenching in clean oil doesn't work. Quenching in used motor oil does
work because it contains free carbon which will dissolve into the
steel bit.

No, sorry. There's no migration of carbon into the hot steel during an
oil quench, dirty or no.

I've been using used motor oil for quenching for most of my life. I
never thought to check if that was a good idea.
https://www.practicalmachinist.com/vb/general/heat-treatment-quenching-motor-oil-157901/
Looks like the consensus is that there's no carbon migration. I guess
I should stop saving my old motor oil.

A lot of backyard mechanics don't understand oil quenching. They think
it's always magically superior to water quenching. But the purpose of an
oil quench is to give a slower quench than water. (Brine gives a faster
quench.) In a properly controlled industrial process, the choice of
quench rate is determined by the type of steel alloy. Some alloys have
the ability to fully harden with a slower quench. Those use oil quenching.

Agreed, except this isn't an industrial process. It's more like a
backyard mechanic fast fix for driver bits that are too soft. I've
only tried hardening a few bits, but the results seem to justify the
effort.

The big benefit is that a slower quench is less likely to warp or crack
the part. This can be important for parts with complex geometry, varying
wall thicknesses etc.

Judging by my grinder spark test on a new bit, the metal is definitely
not high carbon steel. More like low carbon mild steel:
https://en.wikipedia.org/wiki/Spark_testing
https://www.google.com/search?q=steel+spark+test+chart&tbm=isch
It's been a while and I don't recall what I found. I'll run it again
in a few hours and try to take a photo after I figure out how to
protect the camera lens.

However, controlling the amount of carbon absorbed is
difficult. One could easily end up with too much carbon and produce
brittle cast iron.

The diffusion of carbon into steel is called carburizing, and it's a
solid solution phenomenon. Solid carbon atoms _slowly_ make their way in
among the solid iron (or steel) atoms. It's a lot different from water
soaking into a sponge. It takes a long time.

Ok, got it. As I understand it, the diffusion process is much faster
for just hardening the surface (case hardening). Neither the video or
my tinkering allowed sufficient time to diffuse the carbon much below
the surface.

Hardening by slow air cooling is a good compromise between the
original untreated bit, and the various attempts to harden the tip.
However, air cooling only works with steel compositions that are made
for air hardening such as those with high chromium content:
https://en.wikipedia.org/wiki/Tool_steel#Air-hardening:_the_A_series

Yes. Air quenching is much slower than oil quenching, given similar
cross sections. It usually requires even fancier steel alloys.

Heat treating and annealing can always be made more complexicate. I've
never tried it, but cryogenic heat treatment is popular among knife
makers:
https://en.wikipedia.org/wiki/Cryogenic_treatment

BTW, I remember visiting a wire drawing factory producing steel wire for
radial tire belts. Occasionally the drawing process would cause a wire
to break. They had a rig that electrically butt-welded the broken ends
of the wire. But the thin wire air quenched to brittle martensite, so
the rig re-warmed it to temper it or anneal it. It was like this
demonstration of welding a band saw blade, but completely automatic:
https://www.youtube.com/watch?v=xuFpZTUjtmg

Nice video. However, when I do annealing, I don't let it get red hot.
A friend's vintage bandsaw has the same blade welding arrangement. For
when I was trying to make knives, the annealing was done in the
kitchen electric oven. For tool and high carbon steels, I wrapped the
parts in stainless steel foil to keep the carbon in the steel from
oxidizing into carbon dioxide. How it's done:
https://www.keithcompany.com/heat-treat-foils-and-tool-wraps.html


--
Jeff Liebermann
PO Box 272 http://www.LearnByDestroying.com
Ben Lomond CA 95005-0272
Skype: JeffLiebermann AE6KS 831-336-2558

On Saturday, May 22, 2021 at 9:57:11 AM UTC-7, Frank Krygowski wrote:
On 5/22/2021 2:06 AM, Jeff Liebermann wrote:
On Sat, 22 May 2021 10:56:25 +0700, John B.
wrote:

On Fri, 21 May 2021 19:17:06 -0700, Jeff Liebermann
wrote:

Nice, but a little big for a bicycle. I've stripped a few bits,
usually from driving at an angle. I've tried hardening some bits,
which helps.
"Experiment CRASH TEST hardening bit for screwdriver"
https://www.youtube.com/watch?v=Y7RSfVqbjSo (3:00)

Quite simply that guy doesn't know what he is doing, at least as shown
in the film. The quenching in carbon is probably a rather futile
attempt at case hardening and had he submerged the bit in carbon dust
and then heated the whole mess to a red heat and held it there for a
period and then quenched the bit he would have had far more success.
As for his quenching in liquids he doesn't seem to get the bit
anywhere near hardening temperature, i.e. red heat.
+1
He doesn't get it quite right, but I like the method and the result.
However, as you note, he made many mistakes.

Quenching in clean oil doesn't work. Quenching in used motor oil does
work because it contains free carbon which will dissolve into the
steel bit.
No, sorry. There's no migration of carbon into the hot steel during an
oil quench, dirty or no.

A lot of backyard mechanics don't understand oil quenching. They think
it's always magically superior to water quenching. But the purpose of an
oil quench is to give a slower quench than water. (Brine gives a faster
quench.) In a properly controlled industrial process, the choice of
quench rate is determined by the type of steel alloy. Some alloys have
the ability to fully harden with a slower quench. Those use oil quenching..

The big benefit is that a slower quench is less likely to warp or crack
the part. This can be important for parts with complex geometry, varying
wall thicknesses etc.
However, controlling the amount of carbon absorbed is
difficult. One could easily end up with too much carbon and produce
brittle cast iron.
The diffusion of carbon into steel is called carburizing, and it's a
solid solution phenomenon. Solid carbon atoms _slowly_ make their way in
among the solid iron (or steel) atoms. It's a lot different from water
soaking into a sponge. It takes a long time.
Hardening by slow air cooling is a good compromise between the
original untreated bit, and the various attempts to harden the tip.
However, air cooling only works with steel compositions that are made
for air hardening such as those with high chromium content:
https://en.wikipedia.org/wiki/Tool_steel#Air-hardening:_the_A_series
Yes. Air quenching is much slower than oil quenching, given similar
cross sections. It usually requires even fancier steel alloys.

BTW, I remember visiting a wire drawing factory producing steel wire for
radial tire belts. Occasionally the drawing process would cause a wire
to break. They had a rig that electrically butt-welded the broken ends
of the wire. But the thin wire air quenched to brittle martensite, so
the rig re-warmed it to temper it or anneal it. It was like this
demonstration of welding a band saw blade, but completely automatic:
https://www.youtube.com/watch?v=xuFpZTUjtmg

I'm really not that knowledgeable about steel castings though I know it is done commonly. These are generally machines like auto disk brakes and the like. But making steel from iron, the steel has to be rapidly quenched to prevent the formation of a crystalline structure that will fail along the crystal lines. It took Detroit a long time to stop casting entire blocks and machining them for piston bores. Eventually they cast the blocks so that they could press in more perfectly round piston sleeves which were also replaceable.

On 5/22/2021 2:58 PM, Tom Kunich wrote:

I'm really not that knowledgeable about steel castings though I know it is done commonly. These are generally machines like auto disk brakes and the like. But making steel from iron, the steel has to be rapidly quenched to prevent the formation of a crystalline structure that will fail along the crystal lines.

No.


--
- Frank Krygowski

On 5/22/2021 2:14 PM, Jeff Liebermann wrote:

Heat treating and annealing can always be made more complexicate. I've
never tried it, but cryogenic heat treatment is popular among knife
makers:
https://en.wikipedia.org/wiki/Cryogenic_treatment

The cryogenic stuff is another kettle of fish entirely. (Frozen fish,
obviously.) I never understood how it works, and I've been told most
metallurgists don't really understand it either.

Fortunately, I'm retired now, so I don't have to puzzle over it!

--
- Frank Krygowski

On Saturday, May 22, 2021 at 12:57:07 PM UTC-7, Frank Krygowski wrote:
On 5/22/2021 2:58 PM, Tom Kunich wrote:

I'm really not that knowledgeable about steel castings though I know it is done commonly. These are generally machines like auto disk brakes and the like. But making steel from iron, the steel has to be rapidly quenched to prevent the formation of a crystalline structure that will fail along the crystal lines.
No.

You're wrong Frank. Why do you suppose that metal fatigue in steel parts are all crystalized? The work heats the parts to above the point where crystallization can occur, and then the part fails along the crystal lines. http://www.graemecooper.com.au/objec...20x%20234).jpg

On 5/22/2021 2:58 PM, Frank Krygowski wrote:
On 5/22/2021 2:14 PM, Jeff Liebermann wrote:

Heat treating and annealing can always be made more
complexicate. I've
never tried it, but cryogenic heat treatment is popular
among knife
makers:
https://en.wikipedia.org/wiki/Cryogenic_treatment

The cryogenic stuff is another kettle of fish entirely.
(Frozen fish, obviously.) I never understood how it works,
and I've been told most metallurgists don't really
understand it either.

Fortunately, I'm retired now, so I don't have to puzzle over
it!


Engine builders are very enthused about it and the results
are fine, this is not new any longer.

The time/temperature change can be ambient-hot-ambient or
reversed for cryogenic. A lot like accelleration /
deceleration formulae really.

--
Andrew Muzi
www.yellowjersey.org/
Open every day since 1 April, 1971

On Sat, 22 May 2021 11:14:47 -0700, Jeff Liebermann
wrote:

Judging by my grinder spark test on a new bit, the metal is definitely
not high carbon steel. More like low carbon mild steel:
https://en.wikipedia.org/wiki/Spark_testing
https://www.google.com/search?q=steel+spark+test+chart&tbm=isch

Spark test on a cheap #3 Phillips driver bit:
http://www.learnbydestroying.com/jef...Bit_spark_test[1].jpg
Based on:
https://winnmachine.com/2020/06/11/traditional-metal-identification/
Looks like it's low carbon (mild) steel. If that's true, then case
hardening, which adds carbon should work. However, conventional
quench and anneal hardening isn't going to work.

Here's a video how to harden "mild" steel:
"How to Harden Mild Steel? (Impossible!)"
https://www.youtube.com/watch?v=LPVxVpdNWKs (10:00)
However, he cheated by finding a piece of structural "mild" steel,
tested it, and discovered it had more carbon than usual.

I'm tempted to try again, this time with case hardening (pack
carburizing):
"Case Hardening"
https://www.youtube.com/watch?v=f_bXiIfcBWs
Oh-oh. This is going to be rather messy.


--
Jeff Liebermann
PO Box 272 http://www.LearnByDestroying.com
Ben Lomond CA 95005-0272
Skype: JeffLiebermann AE6KS 831-336-2558

On Sat, 22 May 2021 11:58:15 -0700 (PDT), Tom Kunich
wrote:

I'm really not that knowledgeable about steel castings though I know it is done commonly. These are generally machines like auto disk brakes and the like. But making steel from iron, the steel has to be rapidly quenched to prevent the formation of a crystalline structure that will fail along the crystal lines. It took Detroit a long time to stop casting entire blocks and machining them for piston bores. Eventually they cast the blocks so that they could press in more perfectly round piston sleeves which were also replaceable.

100% wrong. Congratulations on a perfect score. This might be your
first prefect score, but I'm sure it won't be your last.

1. We're not discussing castings. These are steel forgings,
extrusions, or stampings.

2. Steel that is rapidly quenched is going to be hard and brittle. If
you want your bicycle steel parts to crack when stressed, by all
means, quench rapidly. Oh wait. None of your bicycles have an steel
parts. Never mind.

3. The piston is not sleeved. The cylinder is what is sleeved.

4. Cast iron cyclinder sleeves are installed in aluminum engine
blocks. The cast iron provides wear resistance. The aluminum
provides low weight and high thermal conductivity. However, todays
"cast-in-place" sleeves are placed in the mold before the aluminum is
poured in. Some are replaceable. Some detail:
https://www.enginebuildermag.com/2013/06/sleeves-liners/

5. I covered the "prevent the formation of a crystalline structure"
in a previous rant. Except for amorphous iron:
https://en.wikipedia.org/wiki/Amorphous_metal
all steel compositions are crystalline.

6. Cracks do not occur along crystal boundaries. They occur along
the grain boundaries. A grain is an area where the crystal structure
is quite regular (homoginous). A grain boundary is where different
grains meet at angles that do not produce strong bonds between grains.
That's where crystals crack.



--
Jeff Liebermann
PO Box 272 http://www.LearnByDestroying.com
Ben Lomond CA 95005-0272
Skype: JeffLiebermann AE6KS 831-336-2558

On 5/22/2021 5:21 PM, Jeff Liebermann wrote:
On Sat, 22 May 2021 11:14:47 -0700, Jeff Liebermann
wrote:

Judging by my grinder spark test on a new bit, the metal is definitely
not high carbon steel. More like low carbon mild steel:
https://en.wikipedia.org/wiki/Spark_testing
https://www.google.com/search?q=steel+spark+test+chart&tbm=isch

Spark test on a cheap #3 Phillips driver bit:
http://www.learnbydestroying.com/jef...Bit_spark_test[1].jpg
Based on:
https://winnmachine.com/2020/06/11/traditional-metal-identification/
Looks like it's low carbon (mild) steel. If that's true, then case
hardening, which adds carbon should work. However, conventional
quench and anneal hardening isn't going to work.

Here's a video how to harden "mild" steel:
"How to Harden Mild Steel? (Impossible!)"
https://www.youtube.com/watch?v=LPVxVpdNWKs (10:00)
However, he cheated by finding a piece of structural "mild" steel,
tested it, and discovered it had more carbon than usual.

I'm tempted to try again, this time with case hardening (pack
carburizing):
"Case Hardening"
https://www.youtube.com/watch?v=f_bXiIfcBWs
Oh-oh. This is going to be rather messy.

Note the 8 hour carburizing time.


--
- Frank Krygowski

On Sat, 22 May 2021 18:28:51 -0400, Frank Krygowski
wrote:

On 5/22/2021 5:21 PM, Jeff Liebermann wrote:
I'm tempted to try again, this time with case hardening (pack
carburizing):
"Case Hardening"
https://www.youtube.com/watch?v=f_bXiIfcBWs
Oh-oh. This is going to be rather messy.

Note the 8 hour carburizing time.

Duly noted at 4:40 in the video. He also mentions that it's 8 hrs to
produce a 1/16 inch thick carburized layer. That might be too thick
for a small driver bit. Maybe half the time for half the thickness? I
probably won't be trying to case harden any bits. Besides the mess,
it will require some equipment that I can't easily borrow, and more
time than I want to spend on the project.


METALLURGY FOR CYCLIST II: Steel is Real
https://www.competitivegear.com/articles/metallurgy-for-cyclist-ii-steel-is-real-pg90.htm

Bicycle Metallurgy for the Cyclist Paperback – January 1, 1990
https://www.amazon.com/Bicycle-Metallurgy-Cyclist-Hayduk/dp/0961897708


--
Jeff Liebermann
PO Box 272 http://www.LearnByDestroying.com
Ben Lomond CA 95005-0272
Skype: JeffLiebermann AE6KS 831-336-2558