Using a surface grinder questions

Take light cuts. I can't emphasize that enough. I watched my boss blow up a wheel and take out a wall when feeding around .010" on tool steel gear cutter bits. Don't force it. If the wheel starts slowing down you are hogging off too much, reduce down feed or cross feed or both. Oh yeah, never start to wipe off the water on the magnetic table until the wheel has -completly- stopped. I lost a couple of knuckle tops that way. Your machine probably has a manual table feed so going too fast won't be too much of a problem. The hydraulic table feeds can really force things and the wheels can't take much of that. Best of luck with it. 73 Gary

Feed as fast as you want..but only take off a few tenths (.0001) at a time. Depending on wheel, and material, sometimes you can go fat and take off up to a thousand..but you will likely wear the wheel fast and get burn marks on your material. Plus the finish may suck as the head bounces.

A heads up. The wheel needs to be dressed with a diamond dresser (cheap) and aways...aways...aways start high. If you screw up and start low..and hit the side of the workpiece..you could grenade the wheel. Not a fun think even if it doesn't hurt you.

Gunner

Rule #35 "That which does not kill you, has made a huge tactical error"

I strongly disagree with grinding instructions you've received. If my opinion matters, here's a link

that will take you to a site where grinding is currently being discussed. My posts clearly state a procedure for grinding that is far superior, and explains why. There is some very good information provided for anyone that desires to learn to grind well.

Harold

This is a problem that can have so many causes that it's almost beyond the scope of a post.

First, how are you grinding? Are you subscribing to the notion that you should constantly down feed your wheel and take large swaths with each pass? You'll never achieve what I consider a good finish by that method. You must learn to grind in a different manor.

Are you grinding dry? Heat alone will give you more problems than you'll ever be able to overcome. If so, no matter what it takes, get your grinder running with coolant unless you're grinding small items like punches. Grinding creates an enormous amount of heat, which must be dealt with. The expansion of the work makes holding a tight tolerance almost impossible, to say nothing of the poor finish you're likely to get regardless of your effort.

Are you grinding soft materials? Cold rolled steel, for example? Soft material never grinds as well as hard material, but you can get a good surface void of waves when things are right.

To change how you grind, I suggest the following:

Think of your grinding wheel as a milling cutter, which it really is. It is a multiple toothed cutter that will cut very best by using a corner. Try grinding your objects by picking up, then moving over to the edge and feeding down a reasonable amount. If you have .010" to remove, and it will come off one side, take .005" and run across your item repetitively, feeding the cross slide roughly .030"/.050" each pass, allowing the corner of the wheel to take all the meat off. Take all your passes in this manner, with no down feed until you're ready for the next pass. By grinding in this manner, the wheel takes all the meat off with the corner, leaving the balance of the unaffected wheel to constantly spark the surface. That yields the best finish, and is actually much faster than grinding by the plunge method. It creates a shoulder on the wheel that must be dressed off when it becomes a problem. You'll know when, because the wheel doesn't cut well. It can be because it's gradually developed a tapered shoulder, or it's loaded. Loading is usually caused by the wrong density of bond or wrong hardness of wheel.

The very best scenario when grinding is that you grind both faces, whether they require it or not. That way you keep stress in balance, so the part tends to remain flat. Try to take equal amounts off both faces, even when it's not necessary. Your reward will be flatter parts. Don't take it off one side then the other, take a cut, flip the part, take a cut, flip the part, etc., until you're to finished size. That's the best way to achieve a good finish and a flat part. Your final pass should be something like .0005", with a freshly dressed wheel.

If you have a manual grinder, you're not nearly as likely to be happy with this process as you might be if you have a hydraulic feed machine. Unless you're involved in fine toolroom grinding, I highly recommend you avoid manual machines. I've done some very difficult toolroom grinding with several hydraulic machines, but can't imagine grinding large surfaces with a manual one. You can turn on the hydraulic machine and grind as I recommend while you're doing other tasks.

Be certain that you have matched the wheel to the work at hand. Aluminum oxide wheels for steel, always. Never silicon carbide. Using a silicon carbide wheel on steel creates a glazed wheel almost instantly, and that generally leaves a wavy surface. Too hard of a wheel does the same thing, and a too soft wheel breaks down so fast it almost always leaves a rough finish.

Wheels that are properly selected will cut without loading and leave a decent finish, assuming your grinder has not had the motor replaced by another motor (that has not been precision balanced), and has good spindle bearings. Even a V belt can cause your finish to suffer. It must run smoothly and not transmit any type of motion to the spindle. The slightest vibration will translate into a poor finish. As little as a few hundred thousandths variation show up as waves in your finish. Use a hard wheel for soft material, and a soft wheel for hard material. Wheels must break down at a proper rate (to stay sharp) in order to achieve a good finish.

Are you running your grinder single phase? You're likely to never get a good finish if you are. The uneven power pulses tend to translate into the finish.

If you can provide more information I may be able to provide some guidelines.

Harold

Excellent post Harold

gunner

Rule #35 "That which does not kill you, has made a huge tactical error"

*Blush*-----

Thanks, Gunner.

Harold

Several comments. First this guy just bought a Delta toolmakers grinder. Its is about as light weight as you can get, so advising the guy to take 5 thou is very bad advice! Believe me, I own the rockwell version of this machine and it won't do it! Period.

Second. This machine is not equiped with flood coolent. Mist coolent was an option. I have never tried using coolent because of health concerns but I'm sure it would work better. I have done a lot of grinding dry with decent results. Definately a step up from the milling machine.

chuck

Wouldn't some coolant options be healthier than the grinding dust?

I own a small lightweight (1500 pounds) 6x12" manual surface grinder. I'm not real good at getting terrific finishes either. My grinder manual says to ease the corners of the wheel with a dressing stone, and this helped quite a bit for me. I've always gone with the .0005" downfeed, wide crossfeed, and I'm going to try Harold's .005" downfeed, .020" crossfeed.

I hooked up flood coolant when I ground in my mag chuck. It somehow got under my table and turned the way oil to jelly. I haven't tried coolant since. Most of the things I grind are pretty little, though.

I'm also planning to try precision balancing my wheels. Eric Snow told me recently that little grinders really work better with perfectly balanced wheels.

Grant

Harold, that is pretty much the way they taught me how to use a surface grinder at work. I'm no longer in that department, but they grind several HSS tools a day for the wickman multi-spindles. Todd

Yeah, but what does Eric Snow know?

The comments (in the post that was copied from a different site) were directed to a person that was operating a B&S machine, not for the owner of a Delta. However, everything stated still applies-------perhaps with a lighter depth of grind. Regardless of how rigidly a grinder is built, surface finish will be profoundly improved by the method proposed. Coolant is a must-------it's not a luxury.

I'm not sure I understand your concern for using coolant and your health. Are you suggesting it's healthier to breath the metal particles than some mist? You want to remain healthy? Quit working with metals. There's a given risk for those that do---------it goes with the territory.

When you suggest you've achieved decent results, try selling your results to a QC department. It's all a matter of what you deem acceptable. My time on grinding machines tells me that there's no way in hell you'll come close to the results of grinding wet----and that includes holding dimensions. Typically, grinding is close tolerance work--work that is rendered nearly impossible when grinding dry. If, on the other hand, you have no clue about working to tight tolerances, perhaps that's not a concern. For me, it was. I'm afraid I'll have to put my years of experience in precision grinding up against your opinion.

Harold

Its pretty easy to wear a half face dust mask to avoid breathing the dust and to clean up aftewards.

I don't know how to deal with mist coolent. Seems like anything wet would plug up a resperator pretty quick and you have to deal possible machine damage by the moisture as well.

No doubt that coolent gives a better finish, but for a small rockwell/delta toolmakers grinder (like I have ) your not going to compete with a real surface grinder anyway.

To me it easier to deal with the devil that I know vs the devil that I don't know.

chuck

Use good judgment in the depth of grind. My comments were (originally) directed towards a much more robust machine, a B&S.

When you use my proposed method, do *not* modify the edge of the wheel. That's no different from a wheel that has already done considerable work. It's the corner of the wheel that does the work by this method. You want it as close to a right angle as possible. It's when it becomes tapered that it becomes necessary to dress the wheel.

One other thing. Again, my (original) comments were directed towards a machine that is built for coolant. I fully understand your reluctance to use coolant if you've had a negative experience----like running coolant on a cutter grinder that is intended to be run dry. I obviously wouldn't recommend coolant on dry machines---but I also wouldn't own a dry machine when coolant was a *requirement* for good success. I practice what I preach.

Harold

Chuck, What Harold says. I sometimes will dry grind a small tool but it is really slow compared to using mist or coolant. I just finished my grinding room and it has two exhaust fans. But having even some mist on the part will actually be better than the fines that come off of a grinding operation. The water will get the fines to clump together into larger size particles. I noticed this helps the amount of dust in the air. Especially when grinding cast iron. Even with a mask you will smell iron for hours after grinding cast iron dry. ERS

What kind of dust mask are you using? Are you sure it will block the particle sizes created by grinding?

Check to see if your table has stops. Otherwise you can crank the table right off the ways, and oops, the table will kick up and smack the wheel!

Tony

"Harold and Susan Vordos" wrote in news:4256092f$1 snipped-for-privacy@newspeer2.tds.net:

I was beginning to think that I was the only person that grinds on a surface grinder that way. I've got a question for you Harold. Have you ever done any double disk grinding? I'm looking for a wheel supplier, and maybe some advise. Very tight tolerance parts on a brand new very accurate machine with auto sizing. I'd sure appreciate any help you can offer.

"Waynemak" wrote in news:jiD5e.139$ snipped-for-privacy@fe06.lga:

The power required is a function of the depth and cross feed. Reducing either reduces the power required. Take .0025" and cross feed .010" and you've reduced the power required by 1/2.