I use a fair bit of O-1 steel and depending on whos catalogue I read it's
either tool steel or hss.

They have different chemical contents and different properties. I use
different tool steels for different applications, sometimes chosen by price
rather than perfectly matching applications. HSS is a bit pricey. What do
you make with the O-1?
--
There are only 10 kinds of people...Those that understand binary and
those that don't.


"Damned if i know" wrote in message
news:PhI7c.126223$Up2.25042@pd7tw1no...
I use a fair bit of O-1 steel and depending on whos catalogue I read it's
either tool steel or hss.

There is a big difference in being able to heat in the home shop. Tool
steel, i.e., O-1 and W-1, is heat treatable in the home shop. High speed
Steel, (Hss) which most commercial tools such as drill bit, taps, dies,
etc. is made from requires a multi-step procedure not ordinarily available
in the home shop. IMO, and from what I have read, "tool steel" is very
adaptable to the more casual heat treatment available in the home shop. In
fact, in the book, "Tool Steel Simplified", from the 30's, recommends using
W-1, then O-1 and only then HSS for the toughest jobs. From my limited
experience there seems to be very little difference in tools made from W-1
and O-1.

A footnote and kudos to Ed Huntress for turning me on to Tool Steel
Simplified!

Bob Swinney
"Tom Gardner" wrote in message
y.com...
They have different chemical contents and different properties. I use
different tool steels for different applications, sometimes chosen by
price
rather than perfectly matching applications. HSS is a bit pricey. What
do
you make with the O-1?
--
There are only 10 kinds of people...Those that understand binary and
those that don't.


"Damned if i know" wrote in message
news:PhI7c.126223$Up2.25042@pd7tw1no...
I use a fair bit of O-1 steel and depending on whos catalogue I read
it's
either tool steel or hss.

Hi Bob,
I use a bit of both and from my narrow experience W-1 seems more brittle
than O-1, It's almost as though it isn't as dense or as well molecularly
bonded. I know that sounds strange. I use W-1 for the cost factor and some
of the stuff like square drill rod that I use isn't available in O-1 unless
I use ground stock...again the cost factor for perishable tooling that gets
consumed anyway.
--
There are 10 kinds of people...Those that understand binary and those that
don't


"Robert Swinney" wrote in message
...
There is a big difference in being able to heat in the home shop. Tool
steel, i.e., O-1 and W-1, is heat treatable in the home shop. High speed
Steel, (Hss) which most commercial tools such as drill bit, taps, dies,
etc. is made from requires a multi-step procedure not ordinarily available
in the home shop. IMO, and from what I have read, "tool steel" is very
adaptable to the more casual heat treatment available in the home shop.
In
fact, in the book, "Tool Steel Simplified", from the 30's, recommends
using
W-1, then O-1 and only then HSS for the toughest jobs. From my limited
experience there seems to be very little difference in tools made from W-1
and O-1.

A footnote and kudos to Ed Huntress for turning me on to Tool Steel
Simplified!

Bob Swinney
"Tom Gardner" wrote in message
y.com...
They have different chemical contents and different properties. I use
different tool steels for different applications, sometimes chosen by
price
rather than perfectly matching applications. HSS is a bit pricey. What
do
you make with the O-1?
--
There are only 10 kinds of people...Those that understand binary and
those that don't.


"Damned if i know" wrote in message
news:PhI7c.126223$Up2.25042@pd7tw1no...
I use a fair bit of O-1 steel and depending on whos catalogue I read
it's
either tool steel or hss.

Well, I finally dug out my electropolishing recipes and typed them in.
Then I looked at the previous calculation I did to substitute battery
acid for concentrated sulfuric acid in the citric acid recipe, and for
shame, I discovered that I had slipped a bit or three and was not using
nearly enough. So now I have to mix up some fresh stuff and see how
well it works before I can really comment on how sensitive it is to
temperature and cathode material. I plan on starting with equal volumes
of citric acid powder and battery acid, and will tweak and test from
there. Anyway, here's what I have from a couple of old vacuum
technology books and other sources.

From Fundamentals of Vacuum, author unknown, which credits Armco Steel
Corp. for the recipe
Citric acid 50-60 parts by volume
Sulfuric acid 15 parts by volume (64 parts if battery acid)
Water to make 100 parts
Temperatu 85-94 deg C (185-201 deg F)
Current density: 0.5-1 amp/sq. in.
Voltage: 6-12 V
Cathode: copper or 18-8 stainless steel

From Vacuum Technology, by Andrew Guthrie
Water 20%
Sulfuric acid 20%
Phosphoric acid 60%
Temperatu less than 80 deg C (176 deg F)
Current density: a few mintues at 5 amp/sq. in.

From the Metals Handbook, 8th. ed., Vol. 2
Water 14% by weight
Sulfuric acid 41% by weight
Phosphoric acid 45% by weight
Temperatu 170-230 deg F (77-110 deg C)
Current density: 200-350 amp/sq. ft. (1.4-2.4 amp/sq. in.)

From the Vacumetrics, Inc. Electropolisher Manual
Distilled water 22% by volume
Sulfuric acid 15% by volume
Phosphoric acid 63% by volume
Temperatu apparently room temperature or simply self-heated because
their unit does not have a heater

The sulfuric and phosphoric acids listed here are the concentrated
liquids. Concentrated sulfuric acid has approximately 18 moles/liter of
H2SO4 (specific gravity 1.84, 96.0 weight percent) while battery acid is
about 4.25 moles/liter (specific gravity 1.25, 33.3 weight percent) or
4.24 times weaker, which means it's much too weak for use in any of the
phosphoric acid recipes and really a little too weak for the citric acid
recipe. Since other metals and salts will degrade the performance,
always use distilled water in these recipes.

A tremendous amount of heat is liberated when concentrated sulfuric acid
is diluted with water. Always start by adding the distilled water to
the mixing tank, then slowly adding the sulfuric acid with stirring,
making sure the temperature does not rise over about 70-80 deg C
(160-180 deg F). Then add the phosphoric acid the same way. The
concentrated sulfuric-phosphoric acid solutions are hygroscopic. They
will absorb moisture from the air and can actually overflow the storage
tank in a matter of weeks if it is not kept well sealed and it's in a
humid room.

To mix the citric acid recipe using concentrated sulfuric acid, start
with about 20 parts of water in the tank, slowly add the sulfuric acid
with stirring, then add the citric acid, and finally add the remainder
of the water with more stirring. Note that 64 parts of battery acid and
50-60 parts of citric acid add up to 114-124 parts, over 100 parts, so
the battery acid really isn't quite concentrated enough to make this
exact recipe. I plan to start with 50 parts of citric acid and 50 parts
battery acid, and then try adding a little more battery acid after some
testing, and then maybe some more citric acid if called for. Given how
weak my current solution is in sulfuric acid I'm sure that equal volumes
will work, and this may solve the poor performance I sometimes get if
the solution is too cool or the cathode isn't copper. This solution is
basically supersaturated with citric acid at room temperature so all
will not dissove without heating, and some may precipitate out each time
you cool the solution but it seems to redissolve okay with heating the
next time the solution is used.

Citric acid is available from www.mcmaster.com and in the canning or
spice sections of some groceries, and battery acid is usually available
at local auto parts stores. The concentrated acids are hazardous
materials and expensive to ship, and some chemical supply companies
won't sell to individuals.

The solution volume needs to be at least five times the workpiece
volume, and preferably much bigger than that (but the electrode spacing
requirements usually take care of this). Otherwise the gas given off at
the workpiece and electrode causes too much foaming and the solution
heats too much from the current passing through it. The cathode area
needs to be several times the workpiece surface area, and the workpiece
to cathode distance needs to be at least two or three workpiece
diameters. Ideally arrange multiple cathodes all around and under the
workpiece. Otherwise the polishing action will be localized on the side
facing the cathode and will be very nonuniform. Additional stirring
also helps make the polishing more uniform, especially with larger
workpieces. For small pieces just stirring it around by hand, plus the
evolved gases, is enough. A magnetic stirrer hotplate is ideal if you
have one, otherwise a lance across the bottom of the tank with several
small holes drilled into it and fed with compressed air works okay for
stirring but accelerates evaporation and makes the fumes worse. I use a
small water bath because I had one and its thermostated, and I use a
small polyethylene bowl sitting in the water bath as my polishing tank.
It gets a little soft at 85-90 deg C but I never try to pick it up while
hot.

In the past I've used lead sheeting as a cathode, and stainless steel is
supposed to work but I have had very bad luck using it with the citric
acid recipe so far. I split some 5/8" copper tubing scraps and
flattened them out to make 2" wide rectangular strips, bent into "L"
shapes, and use at least one on each side of the bowl so there is
cathode surface on opposite sides of and below the workpiece. The
copper slowly corrodes if you store it in the solution (I'm sure it is
dissolved oxygen from air causing this) so remove the cathodes for
storage.

The power supply can be as simple as a variac controlling the primary of
a transformer, with a bridge rectifer on the secondary connected to the
electrodes. That's what I use. I scrounged a variac, bought a surplus
110 V primary 13.8 V at 20 amps secondary transformer from www.mpja.com
(I don't think that exact one is still available), and a 50 V 50 A rated
bridge also from mpja. Put the rectifier on a heatsink, add a small
muffin fan to blow across the heatsink and then across the tank to carry
the fumes away from me, and clamp an ac current mulitmeter to one of the
leads from secondary to rectifier to monitor the current. Mpja also has
a current shunt and dc meter if you want direct measurement. The fuse
in the variac should protect the tranformer but the rectifer seems to
pop much faster than the fuse when I get careless and let the wires
touch or when I'm trying for too much current. The current densities
and voltage requirements are such that I doubt a simple battery charger
will work well, but feel free to experiment with your charger :-). I
use 308L stainless steel welding rod to make hangars, but pay attention
to the currents and note that the composition of stainless steel is
purty close to that of nichrome. Something like 10 amps will make 1/16"
diameter rod glow red in air, and even the 1/8" stuff will glow and
oxidize pretty quickly at 30-40 amps. The portion that is submerged
will usually be okay, cooled by the liquid, but remember that all that
current is entering the workpiece at whatever spot it is contacting the
rod so sometimes you get arcs and burn marks if the connection isn't
perfect. I try to wrap the welding rod around the workpiece when I can,
to get a solid connection and spread out the current. I've had arcs
erode the threads when I tried just sticking the wire into a small
threaded hole to polish a small piece. I have a large alligator clip on
the leads from the rectifer. The negative lead stays on the copper
cathode and I clip the positive lead onto the stainless steel hangar a
few inches above the surface of the solution to keep the clip as
uncorroded as possible, and then I just dip the workpiece into the
solution, turn on the variac and set the current by eye, watching the
bubble streams, and swish the piece around while it polishes. Pull it
every five or ten seconds for a look, and typically ten to thirty
seconds is enough. Definitely a "feel" type of operation but easy to
learn. The workpiece needs to be clean to start with. No oil, grease,
dirt, or fingerprints. Wear gloves while cleaning it with hot soapy
water, rinse well with tap water, ideally give it a quick rinse in
distilled water (if practical), shake the water off and start polishing.
I don't like to dry it first because any spots that form will interfere
with the polishing, and sometimes it helps to swish the piece around in
the solution for several seconds to kind of wash it off and to let it
heat up before turning on the current.

I will post my results with the citric acid battery acid solution when I
have them, but it will probably be a little while before I need to
electropolish anything.

--
Regards,
Carl Ijames carl.ijames at verizon.net