My personal choice has always been with a dressing stick. As much as some
rave on about star dressers, they are very wasteful of grinding wheels, and
difficult to use in getting a grinding wheel to run true, something that is
very important when grinding toolbits. Dressing sticks (the sintered
type, not the solid boron carbide variety) will leave a sharp surface,
almost as good as the star dresser type, and will do it without wasting any
of the wheel. You're likely to not see any difference between one dressed
with a star dresser and the other with a dressing stick in how they cut but
you will see the difference in how well the wheel turns out.
Dressing green silicon wheels (and black ones as well) is very bad for your
health (silicosis). Breathing the dust should be avoided at all costs.
Dressing with a star dresser really compounds the problem because so much
more of the wheel is wasted.
For dressing wheels on a pedestal grinder, they are far superior. Diamonds
leave a wheel very smooth, necessitating greater pressure be applied to get
good grinding action. Wheels so dressed are very poor for grinding tool
steels. You might say that the wheel starts behaving like a bearing
instead of a grinding wheel. A dressing stick, being softer than diamond,
will remove bits by breaking the bond instead of cutting them like a diamond
does. That yields a far better (slightly rougher) surface for off hand
grinding, yet it is easy to get the wheel running true and flat.
Diamond dressed wheels cut very hot as compared to those dressed by a star
dresser. On machine tools with rigid setups and flood coolant, that's not
an issue. The problems of a star dresser have already been discussed, so
what you get is a compromise of the two when you use a dressing stick.
Dressing sticks are generally made of silicon carbide (or they may be boron
carbide) and resemble a hand stone, usually about an inch square, six inches
long, very coarse, perhaps 24 grit, and not expensive. The only negative
effect of using one is that they have a slight tendency to dull abrasive
grains that do not get knocked off the wheel. The surface they yield is
a good offset, though, so they are a good dressing device, especially for
grinding HSS. I highly recommend one for any shop.
yes, I've noticed that. but, having only a diamond dresser (all I
could get would you believe) I'll not give it up. out of true
grinding wheels give me the absolute heebies
swarf, steam and wind
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And there's no need to. Using the diamond to get a wheel running true is
the best of all worlds. The trick to getting the wheel to cut freely is
then to touch it with the dressing stick, which roughens the surface every
so slightly, making it cut much better. For a few bucks you can see for
yourself. I promise you you won't be disappointed.
I kinda missed where this thread was going. Are you advocating use of
a stick for touch-up after truing with the diamond on my surface
grinder and on my Black Diamond drill sharpener?
You know, I've got some dressing sticks I picked up with wheel stones
at auctions. At least one white and a few black, but never used any
of them. Sounds like I should learn. Does the stick "colour" mean
anything we should know about, say relative to colour of the wheels?
On Tue, 6 Jan 2004 01:55:53 -0800, "Harold & Susan Vordos"
No, never for machine type grinding, that defeats the purpose of the
diamond. Conditions on a precision machine are far different from offhand
grinding, though. I'm not certain when diamonds became the dressing tool
of choice, but there was a time when precision grinders were dressed with
star dressers. In today's demanding world of precision and fine finishes,
that wouldn't fly.
The point of my post is that dressing wheels with a star dresser is
wasteful, and achieving respectable results can be difficult. A diamond
works very well for truing the wheel, but the superior finish it leaves on
the wheel creates a couple problems that are not in the best interest of
offhand grinding, especially tool bits. Because of the slick nature of a
diamond finished wheel, it takes considerable more pressure to get the wheel
to cut. It also cuts one hell of a lot hotter. Anyone that knows
enough to run a cutter grinder knows that wheels are hand dressed when
sharpening end mills. That prevents over heating of the cut, and the wheel
demands dressing often to maintain the cool cutting condition. The
same principle applies to offhand grinding. By using a dressing stick,
the wheel is slightly roughened, which lowers cutting pressure tremendously,
and heating as well. That is not to say that diamonds don't have a place
on cutter grinders, or on pedestal grinders, but you have to know when to
use one, and when not to. There's nothing wrong with using a diamond to
get a wheel running true, but it should be slightly roughed up with a
dressing stick before using it to grind offhand. If that's not right, then
the shop where I was trained did it wrong for years.
Fine grained dressing sticks that are white are primarily intended for
dressing diamond wheels. Yeah, I know, that sounds nuts, but diamond wheels
get loaded with particles and get glazed such that they start not cutting
well. By running a fine stone on the diamond, the crud is removed and the
wheel surface restored. You're not really doing anything to the diamond,
and if you do, you're doing it wrong. The dressing operation should do no
more than clean the wheel, and the diamond tends to remove material from the
dressing stick, as it should be. You don't want to remove the matrix bonding
the diamond for obvious reasons. Dressing diamond wheels should not be a
prolonged operation, one should stop the moment the wheel is cleaned.
The dressing stick I used for years for that purpose was black in color, but
a friend recently gave me a new one, which is white. The black one is no
doubt silicon carbide, the white one aluminum oxide. Both will clean a
diamond wheel, and I have no idea why they are made from both abrasives.
In the scheme of things, the aluminum oxide one would certainly be softer,
kinder to diamonds, but the hardness difference between diamonds and silicon
carbide is so great I'm not convinced it makes a significant difference.
If you have in your collection of dressing sticks one that is very coarse,
made of shiny black bits of abrasive, it is most likely a silicon carbide
stick made for dressing aluminum oxide grinding wheels. There would be no
harm in trying it on a grinding wheel on your pedestal grinder, which is
where I highly recommend these items be used. If it is a dressing stick,
the wheel is readily abraded. I suggest you not use a white one on an
aluminum oxide wheel, use only a black one.
It was common practice for us to use dressing sticks to relieve the sides of
wheels when we had face work to do. Even on precision grinders, face work
is generally done with hand dressed wheels, and for the same reasons,
keeping heat down. It was not uncommon to get heat checking on faces of
heat treated tool steels otherwise, so how the wheel was dressed was rather
critical. Face grinding keeps a lot more of the wheel in contact, so more
heat is generated. The rapid heating and subsequent quenching by coolant
was the source of heat checking. Hand dressing is almost mandatory for that
operation. That would be true if the side of the wheel was used to kiss
the face. If the wheel head is turned, a right angle is dressed on the
wheel and grinds both the cylinder and the face with the periphery of the
wheel. By grinding that way, the problem of heating is reduced to
Hope this helps~
I agree with Harold in all respects save one. If you have a badly worn
bench grinder wheel and you want to get it flat again, a star dresser will
do the job much faster than anything else. That's why I keep one in my shop.
Harold & Susan Vordos wrote:
I agree that the star dresser could be faster under that circumstance. I'm
not convinced it would beat a diamond, though. Another very good use for
the star type dresser is on larger wheels used in welding shops. Star
dressers, just like diamonds or dressing sticks, have a place. It's a wise
person that knows when to use the right one.
Hey Guys, and Fitch (I hope),
OK....my turn for Questions and Answers (hopefully) on the rotary
convertor I'm about to attempt to hook up.
First.... the question.... I have a 3 phase wound rotor motor to use
as a convertor for 220VAC single phase to 220VAC three phase. How do
I "hook up" with this? Do I short-out the slip-rings and just
consider it a squirrel cage, or do I wire to both the rotor and
stator, or wire to the stator and take the three phase off the
slip-rings (actually I don't think THAT works), or.....or....or????
Now for the description, for those that are still reading.
Long-winded, as usual, but it helps me out to do so. Sorry.
I was fairly recently blessed with two freebie 20HP motors. Except,
different to any earlier postings here that I recall, these are wound
These were in use on AC geared traction elevators, and were wired for
"Dynac" use, which is a 1960's method of getting speed control almost
like a DC operation from AC motors, using some special mechanical
features and controls and incorporating either 2 or 4 medium size
thyratron tubes. Gladly get into details for anybody that wants, but
this is merely explanatory/descriptive here as I won't be using any of
The motors were made by Bull Motors, England, as 208 VAC, 3Phase,
60Hz, 1150 RPM, 67 Amp, all copper windings. One pair of 1/2" X
5/8" brushes on each slip-ring. One of the two motors has had the
stator redone locally fairly recently (and that's the one I want to
use), and in the external junction box it just has three stator lead
connections ,and three direct to the slip-rings connections for the
rotor. The second motor has some BAD gooey rubbery disintegration of
the 3 of the wires as they feed through the motor frame to the stator,
and so I don't want to use this motor; BUT.. it has a small Bull
original print diagram in the junction box showing that the motors had
9 leads... 3 to the slip-rings for the Delta connected rotor, and 3 to
the STAR stator field pieces and 3 connected together to form the
STAR. I assume that the STAR shorted leads are done internally on
the rewound motor I hope to use..
These motors are fairly beasty things, with about a 20 pound flange
coupling still in place on a 2-3/8" rotor shaft turned down to 2" for
the coupling. I may well cut the couplings off later, but I can't
pull them in situ here without a largish puller. And I've wondered,
and maybe somebody can tell me, if the heavy coupling would actually
assist in strengthening the output after reaching full RPM. If so,
would heavier be even better? I can pour lead in to do that!. In
original operation, this flange was coupled to a special 20" diameter
X 12" long brake drum with1" thick flange with the external diameter
having pressed in copper bars through it parallel to the motor shaft,
so they were pretty heavy and added a lot of inertia "smoothing" to
the speed variations in operation.
Any suggestions? Or do I still need to call Marty for the rotary he
has for sale????
ps..... Also posted to modeleng-list
The 3 leads from the wound rotor would normally go to a
starter/speed control box. The box would have a sequence
of resistors that would be inserted between the leads
coming off the rotor, with maximum resistance for starting/
slowest speed and zero resistance for max speed.
The difference between starter service and speed control
service is that for speed control, the resistors have to be
able to dissipate heat on a continuous basis. For starting
service, they are rated for intermittent duty and don't have
to be as big, wattage wise.
I don't have a clue as to what a good starting resistance would
be. If I were doing this, I'd probably try 100-200 watts
of light bulb for each resistance to see if it would start.
I can check my books at home tonight. I have an old Audel's
book on elevator controls and it might have more information.
How about some of those old screw-in heater elements,
that have light bulb bases, but are conical ceramic
with resistance wire wound around them, for old time
================================================= please reply to:
JRR(zero) at yktvmv (dot) vnet (dot) ibm (dot) com
Or one of those water heater elements that you some times see in the
surplus catalogs. The important part is to take that resistance out
of the circuit and short the rotor leads together once its running.
The low speed (relatively) wound rotor motor with the rotor leads
shorted together to minimize rotor losses ought to make a great
converter once its running.
Looks like some items of interest for some of us. No lathes or mills
though, but have a quick peek.
cross-posted to modeleng-list
*Construction & Concrete Equipment*
Close-Out Liquidation AUCTION
Vermu Contracting Ltd (Waterloo) & Others
BRESLAU AIRPORT ROAD AUCTION COMPLEX
5100 FOUNTAIN ST North, BRESLAU (Kitchener)
Sat May 1st 9:00 am
Visit our online flyer at:
For dressing the wheels on bench grinders I have always liked the clustered
diamond ones. The rectangular ones about 3/8 x 1" with a handle, looks like a T
with a real narrow top.
How's the snow, Harold?
Aside from the way-too-smooth surface created, they do an outstanding job.
I still prefer a dressing stick over them. Or both, one to get the wheel
running smooth and flat, the other to produce a better surface for grinding
manually. If you haven't done it, it's hard to understand. I have. I
do. Lots of converts to "doing it right". :-)
Yeow! 15" on the ground and it's snowing as we speak, with below freezing
temps over the past couple days. Weatherman said we can expect the most
severe snow storm we've had in years. It's going to be a long night!
Supposed to turn to rain after a foot or so drops in the next 24 hours.
Worst weather I've seen since moving here in '96. Figures! <g>
Hmmm.. my rememberer is too slow, but my forgeterer makes up for it by
being too quick!! So I can't recall what it was you did to protect
the house project for the winter. Is it something that you have to
keep brushing the snow off to stop accumulation? Hate to think you
and the missus have to do a "navy watch" system every night you get
some frozen precip.
Take care. Don't overdo it.
On Mon, 5 Jan 2004 22:20:45 -0800, "Harold & Susan Vordos"
I ended up draping a string reinforced visqueen tarp over the interior,
which is supported in the center by the floor trusses of the second story of
the house. The sub-floor is not installed. The tarp drains from the
center, and there are temporary crickets directing the water towards the
drain, which is 3" diameter drain pipe. It's worked pretty well so far, but
anything that hits the roof ends up going down the drain, nothing comes off
the sides because the tarp is, for lack of better description, a very flat
funnel, only about 20" taller on the edges than the center. In order to
prevent snow from tearing it down, I've had to get up on a ladder each day
(that it snowed) and reach in as far as I can with a broom and drag the snow
off the outside edges. It's complicated by the rebar that's on 15" centers
sticking up. the rebar, however, is the anchor point of the tarp, so it
serves a useful purpose in spite of being a PIA. Of all years to get record
snow, naturally it had to be this one. We have about 19" on the ground
now, it's put down 4" since late last night. If we make it past today,
we're supposed to warm up. It's been interesting, Brian! What really
irritates me is last year we had no snow.
I appreciate your concern.
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