The "well dressed stone"

[thomas harris]

Ive always been one to hop on a grinder and fix tools when needed. Now that I need hss lathe bits it's gone to a new level. I finally grabbed a wheel dressing stone. This is reallly nice! A real pleasure to have that surface the way I need it. Flat on the front and an edge on the sides. Now all I need is someone next to me yelling " not that way moron". I'm sure I'll pick up a few wrong techniques, but the bits are definitely cutting and looking better. I think the dressed stone will make sharpening hss twist drill a lot easier too. I used a Drill Doctor before, but it's usually hidden in the shop somewhere, while the old bench grinder is always right there waiting.

[Harold_V]

Don't know if you read a few of the posts I did some time ago on grinding HSS and grinders, but I recommended a dressing stick in them. For those of us that have run cutter and precision grinders for a living, I'm not sure we could survive without them.

While diamond dressing is a great way to true a wheel, it leaves a great deal to be desired for offhand grinding. It may run true, but it cuts hot and requires considerable pressure on the grind in order to overcome the smoothness of the wheel. Those are non issues with a machine with coolant. A dressing stick has the ability to yield a smooth wheel that is almost perfect for offhand grinding. It's hard enough to dislodge dull bits of abrasive from a wheel without being able to cut them cleanly as a diamond does.

Congratulations on your new discovery.

Harold

[thomas harris]

I read the sharpening threads and gleaned much info from it. The hard part is when one tries to grasp a mutifaceted cutting edge with only a few pictures or just a verbal explnaition. The wheel dresser I picked up was indeed a silicon carbide variety and not diamond.

[Harold_V]

I read the sharpening threads and gleaned much info from it. The hard part is when one tries to grasp a mutifaceted cutting edge with only a few pictures or just a verbal explnaition.

Those are the kinds of things that are hard for me. I can do the grinds, but I have some trouble describing them to those that don't have the same understanding. Hopefully you got the impression that when you grind each face of the tool, that it is one common plane. That was what I tried to convey---in other words, to not chop up the grind with multiple faces. They look lousy and are much harder to stone. Worst of all, if you're really bad at grinding, you often find that the one that matters the very most, the one near the cutting edge, is often negative----so the tool won't cut. I've seen tools ground that were chopped up badly, with the center of the tool the contact point. I guess if there's anything good that can be said about the tool, it would have to be that you won't wear it out using it!

The wheel dresser I picked up was indeed a silicon carbide variety and not diamond.

I assumed it was, from your description. The only reason I made mention of diamond was for the benefit of others than may not have been down that road. All too many think that a diamond dressed wheel is the ultimate------and it is-----but not for off hand grinding. I like to say something about that very subject at every opportunity-----which can be helpful for the guy that hasn't been so informed before.

Harold

[miker]

Hi, which particular sticks would be best suited to the home shop A/O 6 inch wheels. There are a lot to choose from.

http://www.ind.nortonabrasives.com/Medi ... Sticks.pdf

Rgds

Michael

Australia

[Harold_V]

Michael,

A good choice would be any of the 1" square sticks in either 20 or 24 grit. The coarse grain is used for dressing conventional wheels, with the fine grades reserved for diamond wheels. You will find an acceptable choice in the vitrified dressing sticks S/C portion of the pdf. file. on page 1. An example of a good choice would be one of the 37C20SVK sticks.

While I am a strong supporter of Norton products, you may find an import stick will serve your needs quite well. Don't discount them if you find one available. I've seen them offered for a fraction of the price of name brands.

A dressing stick, used routinely, will last for years----you need not buy more than one, and there is little advantage, if any, in having more than one type. Avoid the boron carbide type, small in size, for they tend to dull with use and begin performing quite poorly. If you can keep a sharp corner on such a stick, using a diamond wheel, it will serve quite well, although I question the value when cost is considered. In general, a wheel so dressed will not be as sharp and cut nearly as well as a wheel dressed with a sharp corner of the silicon carbide variety.

Harold

[miker]

Thanks very much for the reply Harold. I will start chasing down a Dressing Stick.

Rgds

Michael

Australia

[david freeman]

First things first , silicon carbide wheels are cheep , they need to be dreesed often and generate alot of heat and should not be used for softer mat'l's like copper , brass and aluminum. Alundum wheels are a step up and will grind all common mat'l's easily except carbide . For HSS you can't go wrong with an aluminum oxide wheel . Rough with 60 or 80 and finish with 120 or 150 . Honning the edge is the key to a good cut . Don't get carried away with the tool nose radius . .008 to .010 is ideal for finishing . Dressing sticks should be used to finish the dress when working free hand on finishing wheels . Using a star wheel will expose a fresh cutting surface quickly . Call a locale Tool Crib for cost and details .Do not over heat HSS . You should be able to hold the ground section in your hand . Quench the tool in water often .Keep the wheel dressed and don't get in a hurry !!! Buy a Machinist Handbook , it will give details on rake angles for cutting various metals . .002 thou per rev. is a good starting feed rate for light machines . Rigitity is a must .
Diamond & Vitrified grinding of carbide is a whole other animal .

[Harold_V]

Using a star wheel will expose a fresh cutting surface quickly

While a star type dresser is the best choice for preparing a wheel surface for grinding, I do not recommend them.

For starters, the grinding system I endorse uses no grinding rest, so it's next to impossible to apply such a dressing tool.

The second problem is that they are not easily mastered, even when in good condition. A large amount of wheel can be wasted attempting to get a wheel running smoothly. A bouncing wheel is virtually useless for the type of grinding I endorse.

Star type dressing attachments dress by hammering, breaking bonds of the grain. It's the best possible way to remove dulled abrasive ----- but it comes at a price----often in the form of a bouncing wheel, and a lot of wasted wheel while attempting to eliminate the bounce. That can be avoided by not using a star type dresser.

A wheel dressed with a proper stick will come very close to performing at the same level of the star dresser------and will remove very little of the wheel in the process. Not only do you save the wheel, but you also minimize the amount of harmful dust in the shop. One must use good judgment when using the stick, it goes without saying. Placing a broad, well used stick surface on the wheel can have a dulling effect on the grain. Sharp edges of a sintered stick work best.

A bouncing wheel is very best trued with a diamond---followed up with a dressing stick to "rough" the wheel so it cuts freely. A diamond dressed wheel is a poor surface for off-hand grinding---requiring too much tool pressure from the operator. Not only does the wheel cut hot, it lends more danger to being harmed by slipping and hitting the wheel with one's fingers.

Silicon carbide wheels should not be lumped as a group----the wrong message is being sent to readers. Green silicon carbide wheels are formulated for very hard substances-----tungsten carbide and the grinding of various types of rock--------but black silicon carbide wheels are the wheel of choice for soft metals---aluminum, copper, copper alloys. Neither of them are recommended for grinding of the steel family-----although the black one is the recommended wheel for cast iron.

There's much to know about proper wheel selection. Some of it is opinion, most of it is hard fact.


Harold

[david freeman]

Norton has a great web site . Well worth the time to read and explore . With all the diversity in this world you will find wheels in any color of the rainbow. Norton makes a great black aluminum oxide wheel , a gray, a light blue , white etc . for grinding steel . These are the synthetic equivalant of corundum . Rubys and saphires are made of corundum and were crushed to make sandpaper & grinding wheels along with garnets and emory until aluminum oxide was introduced . I was at Gem Mountain in Philipsburg Montana last month and was appauled to learn as late as WW2 they were still mining the gems and crushing them up for sandpaper .
The Geen or Black silicon carbide wheels are different due to the purity . They far exceed the inexspensive gray , darkish blue wheels you can buy for a few bucks and are great for carbide and non-ferous mat'l's .
A star wheel crushes the surface exsposing sharp crystals . A steady rest is a requirment . The dust is hazerdous and a resperator or face mask should be used . Carbide dust is at or near the top of the list .

[Harold_V]

The Geen or Black silicon carbide wheels are different due to the purity

They are different in color to differentiate them from one another.. neither is an inferior copy of the other. Green silicon carbide wheels are made intentionally soft so they degrade rapidly, keeping sharp crystals exposed. They lend themselves to grinding very hard substances, and fail miserably on soft substances. That's in keeping with the concept of a hard wheel for soft objects, and soft wheels for hard objects. Softness in this case relates to the bonding of the wheel, not the abrasive from which it is made.

Silicon carbide wheels should not be confused with aluminum oxide wheels-----which are the wheels of choice for grinding steel----the reason being that silicon carbide readily dissolve in steel at heat----thus, in spite of being harder than aluminum oxide, it doesn't grind steel as well-----failing almost instantly. That's the same reason diamond is not recommended for grinding steel. Run them slow enough, it's not a problem.

They far exceed the inexspensive gray , darkish blue wheels you can buy for a few bucks and are great for carbide and non-ferous mat'l's .

The wheels of which you speak are not silicon carbide, and are not great for non-ferrous. Silicon carbide is the choice for non-ferrous. They are aluminum oxide, and not suited to grinding hard materials, particularly carbide. They are clearly the wrong choice, and don't even do much of a job on HSS. Generally they're too hard. Soft silicon carbide or diamond is the proper wheel for carbide.

A star wheel crushes the surface exsposing sharp crystals .

Yes, by hammering. I'm not a stranger to star dressers, which is the reason I don't like them.

A dressing stick displaces grains, it does not cut them, unlike a sharp diamond. In a sense, it, too, dresses by the same principles as a star dresser, and will yield a wheel very much like one, assuming you don't apply it improperly.

I ran grinding equipment for years-----primarily precision grinding, although I had a brief excursion in cutter grinding as well. I'm very familiar with grinding wheels and their characteristics, at least "old school" wheels. While a dressing stick was a part of our tool kit for precision grinding, it was impossible to run a cutter grinder without one. If you have never used one, may I suggest you give one a go before passing judgment? You may come to understand why they enjoy so much popularity.

Harold