What is the proper tool/method

of dressing the green silica(?) grinding wheels used for Carbide lathe tools?
Many thanks.
Roger in Vegas Pets have owners. Cats have staff.

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tools?
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.
Harold
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Harold & Susan Vordos wrote:

I'm not familiar with those. How to they compare to a diamond dresser?
Ted
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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.
Harold
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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
-- David Forsyth -:- the email address is real /"\ http://terrapin.ru.ac.za/~iwdf/welcome.html \ / ASCII Ribbon campaign against HTML E-Mail > - - - - - - -> X If you receive email saying "Send this to everyone you know," / \ PLEASE pretend you don't know me.
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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.
Harold
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Hey Harold,
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?
Take care.
Brian Lawson, Bothwell, Ontario. XXXXXXXXXXXXXXXXXXXXX On Tue, 6 Jan 2004 01:55:53 -0800, "Harold & Susan Vordos"

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Hey Brian, 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 manageable levels.
Hope this helps~

You too!
Harold
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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.
Grant
Harold & Susan Vordos wrote:

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shop.
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.
Harold
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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 rotor motors.
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 that mode.
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????
Take care.
Brian Lawson, Bothwell, Ontario.
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
ps..... Also posted to modeleng-list
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Brian Lawson wrote:

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.
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The cold resistance of the bulbs might be too low to allow soft start. Something on the order of 20 to 40 ohms sounds about right for starting a 20 hp wound rotor motor.
Gary
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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 space heaters?
Jim
================================================= please reply to: JRR(zero) at yktvmv (dot) vnet (dot) ibm (dot) com =================================================
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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.
Fitch
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Hey guys,
Looks like some items of interest for some of us. No lathes or mills though, but have a quick peek.
Take care.
Brian Lawson, Bothwell, Ontario.
cross-posted to modeleng-list XXXXXXXXXXXXXXXXXXXXX
*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: http://www.mrjutzi.ca/2004-05-01.html
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Harold & Susan Vordos wrote:

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.
michael
How's the snow, Harold?
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snip---

clustered
like a T

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>
Harold
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Hey Harold,
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.
Brian Lawson, Bothwell, Ontario. XXXXXXXXXXXXXXXXXXXXXX On Mon, 5 Jan 2004 22:20:45 -0800, "Harold & Susan Vordos"

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Hey Brian,
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.
Harold
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