No, it's really not a problem. I've taken as much as .050 in a pass. You just have to be careful with your cross feed. Grinders really need to be fed hard in order to cut well. The wheel NEEDS to break down so that you're always cutting with sharp grit. Grinding too slowly will actually generate more heat because the grit gets dull instead of falling off the wheel. You can tell by the sound of your grider if you're feeding too aggresively. Obviously there are limits. If the wheel disentigrates, and lodges into your neck, take smaller passes. :)
That depends on the size of your part. The thinner the part, the more you rough, and the more accuracy you need, the larger the demand for coolant. If your part is a couple of inches thick, and you're only taking off .01 or so, coolant isn't that big of a deal. If you really got to hold accuracy though, it's a good idea to let your part cool before taking the final pass.
It's a far less efficient way to grind. You're better off with a lighter depth of cut, so the wheel isn't crowded . Keep in mind, the depth of cut dictates the amount of wheel loss when dressing.
You
Exactly------but that's more an indicator of the wrong wheel hardness than feed rate. The wheel must be friable enough to break down when the individual bits dull, not before. By exceedingly heavy cuts, you crush the wheel prematurely. You think you're gaining ground on the project, but you're just wasting the wheel.
Grinding too slowly will actually generate
Again, that's a sign of the wrong wheel. A light cut doesn't dull the wheel-----if anything--it prolongs the useful life, actually working the wheel instead of reducing it by crushing. I'm no stranger to precision grinding, be it cylindrical, internal, surface or centerless. I've even spent a little time on cutter grinders.
How fast the edge moves across the wheel is a more than adequate indicator of how the wheel is performing. If it won't tolerate a feed of .030" or slightly greater, the depth of cut is greater than it should be. That's been my experience, and has served me well. Understand I'm not timid in my approach to grinding, but I'm wise enough to understand that sacrificing wheel life for the appearance of kicking butt is a false economy.
Do that when the wheel breaks down too quickly and you don't have to worry about anything in your neck. You don't have to have a catastrophic failure to know when you've gone too far, you simply have to understand what the wheel is telling you-----and to be able to discern the difference between a loaded and dull wheel.
Efficient grinding, *if size is critical*, relies on coolant, full stop. It has nothing to do with the size of the part. Ten thou off a piece that's a couple inches thick is going to raise the temperature of the part to some degree----like it or not. There's a reason gage labs are operated in temperature and humidity controlled rooms----because miniscule temperature changes make a difference. The closer you come to duplicating those conditions, the better your chance of achieving your objective. Sure, you can grind dry------and guess at the amount of heat in your work------or even give the part an hour to stabilize. I see no advantage when coolant prevents the problem and allows for faster and cleaner stock removal, with size control left to direct measurement, not chance. I've ground enough to know that doing so without coolant is a mistake, but then I also had to work to specifications. Given a free reign of size, maybe you're right.
Before you jump to conclusions about my comment, yes, I understand that there are exceptions -----just like there are exceptions to using manual versus hand operated surface grinders. I'd rather fight the hydraulics when grinding intricate pieces on an intermittent basis than fight hand grinding on a regular basis. I'm funny like that.
Most of that wheel loss happens at the leading edge. I never worry about dressing to 100% wheel width. The wheel can be dressed to 80% width within about .010.
Harold,
You're obviously very experienced. I don't mean any disrespect, and I KNOW that your grinding technique will result in a quality part in a resonable amount of time. But, I also know that back in the day before high quality carbides and machines that could run them, there were many instances that I could rough a block on the grinder as quickly as many people could mill them. Tollerances of +-.0002 were often held without coolant. While I don't believe that your technique is necisarily wrong, I don't believe that mine is either.
I've dressed more than my share of wheels where I didn't eliminate the edge and have paid the price in keeping with what I consider a mistake. Once the edge fails and begins to taper, it doesn't grind well----not well at all, and encourages rapid degradation of the new edge, which really isn't an edge at all. In a nut shell, I wouldn't do it, nor would I expect the wheel to perform well if I did. Understand I've even run a centerless, with it's 24" diameter wheel and 6" of width. It just doesn't work well when taking huge cuts, which likely accounts for production grinding shops running three or more centerless grinders in series to turn out a finish ground part. They don't take large passes per wheel, because it just doesn't work well. That, in no way, implies that the machine can't do it.
YMMV----if for no other reason, you're using a grinder like a mill----for stock removal. The only time I saw that done with success was when a friend was running a large Blanchard with 250 horse on the head. They used to use a back hoe to remove the swarf from the settling pond.
Nor do I. After all, it's all in one's perspective and objective. I'm coming from the position of having to work to tight tolerances, and was trained accordingly. I also reaped the rewards of having learned to grind properly. If you use procedures that introduce questions, you work by chance. I was taught early on that that wasn't an acceptable scenario. Bear in mind, I also worked where there was no need to use a grinder as a mill. We had proper machines for the work at hand.
Given a project that doesn't require the best finish, nor to be held to exceedingly tight tolerances, of course, you can grind by pretty much any method that suits a person----even a disk grinder will suffice given a loose enough tolerance. The problem here is that if one learns to ignore the finesse of fine grinding, it's a chore to achieve tough work when called upon to do so. A good grinder can easily do rough work if required, but it's a whole different matter to expect a lesser skilled and experienced person, particularly if they have never been schooled in finesse, to turn out tough work. I'm sure you've seen that in your years of die making. My years in the trade have taught me that not everyone can turn out quality work.
In today's society, it has become more than acceptable to turn out mediocre work-----regardless of the arena. Making a fast buck is far more important that doing a good and proper job. Builders turning out shoddy houses, machinists turning out work that is marginally compliant with prints, etc.. I'm sure you get the idea. That is far and away from anything I find acceptable in my life and business practices, and always has been.
I ran my small commercial shop for 16 years and dedicated myself to excellency. Didn't always achieve it, but that wasn't due to lack of trying. Sometimes it doesn't matter how hard you try, you fail. I never worked for the money, always for the pride in doing a job well. If I happened to make a little extra along the way, that, too, was acceptable, and it goes without saying that I had to make a living.
There's room for all types of workmen, but when the chips are down, those with exceptional skills and work habits will find employment when the others are on the outside looking in. I've yet to meet a person that could fake skill. You have it, or you don't. I try to encourage folks to learn the best way, for they can always play down, but it's almost impossible to play up.
If you're stepping over .035 or more, the sharp corner you created isn't relevant. Essentially, you're plunge grinding. As the edge wears, there's a new spot on the wheel to take it's place.
In a nut shell, I wouldn't do it, nor would I expect the
Perhaps this is where our experiences differ. I've never run a centerless grinder. I have spent many hours creating complex contours on a surface grinder though.
A grinder is a metal removal tool, just like almost all other equipment found in a machine shop. That's what it's made for.
We had an old blanchard. It wasn't nearly that size though. It had the nastiest coolant in it you've ever smelled because there wasn't a good way to drain the tank. One day, I threw my part off the machine. :( I had to lay on the table, reaching my arm down inside the machine into the muck and foul for nearly an hour before I could find it. :(
Oh, the good ol days. :)
The procedures I use don't introduce questions. The results are very predictable.
So did we. Where I worked, the proper machine was the one that got the job finished to the proper quality in the shortest amount of time. Anything less is stealing, or lack of skill.
My experience comes from building plastic injection molds. We often made intricate cores and cavities with complicated seal offs. We had to form grind angles and radii that would have to fit properly with mating parts. These parts were ground after heat treat. The blocks were nearly always above 50 RC. In those days, you had 2 choices. Grind it, or burn it. Grinding is MUCH faster.
----even a disk grinder will suffice given a loose
Sure, I can't disagree with that. When it comes time to hit the numbers, you've got to slow down and take your time. I'm just saying that if you've still got .050 on the part, why mess around with .005 passes?
My experience in that regard, and it's never varied, is that the edge doesn't break down uniformly, but instead forms a taper of sorts, leaving way too much of the wheel in contact with the work. The surface finish, which, to me, has always been just as important as the degree of precision, goes straight to hell. On small grinders (that use 7" x 1/2 wheels), the wheel starts hopping instead of grinding as it should. I've run various makes of grinders and have had almost identical results with them. It's dead easy to know when it's time to dress the wheel.
I've seen more than my share of surface grinding accomplished by folks that don't give a damn about surface finish, and it's not for me. I take far more pride in the work I do than to turn out finishes like that. Again, there's not necessarily a right or wrong way----it's just a matter of my personal pride. Some folks do as little as they can to get by. I tend to do far more. That's what set me aside from others when I was in the trade.
The principal doesn't change-----what is troublesome with a centerless is just as troublesome with a surface grinder-----you're just willing to tolerate the trouble. I'm not. It's clearly a difference in how each of us was trained, and the systems we've been willing to assimilate.
I've studied the complexities of a spoon (or fork) mold, if you're alluding to that. Yes, I understand, but I'd still do it with more finesse. Grind lines would need little, if any, polishing. It's the way I think. Yes, I was competitive, but only because I wasn't trying to make more than I was worth. My shop never suffered for work, and from the best of sources.
But it is typically used within it's real capabilities. Suggesting a depth of cut of .05" on a 6 x 18 grinder is telling folks that they can do it safely. That's simply not true, and could lead some to tragic ends. There's one hell of a difference between you grinding the outside of a die that's 2" thick and the guy that trying to flatten a small item. Keeping it on the chuck tends to be important, and deep cuts make that impossible.
Tank? Heh! Did you notice I said *pond*? This dude had made a coolant setup outside his shop, literally a pond next to the building. This was in Utah, where winter can be tough, temps below freezing both day and night, often for a few weeks at a time. I have no clue what he did in the winter time. I never worked with this guy, but subcontracted from the shop where I met him (working in progress), before he started his business. By then, I was out of the trade, but I stopped by his shop to pay a visit, and that's when I saw his operation. My time on a Blanchard is very limited-------one job only, and was on a machine in a shop that allowed me to use it to complete the job In question. That particular (old and tired) machine was nothing short of a pig. Wouldn't grind parallel, no way. I struggled through a .001" tolerance job and never went back. I'd had jobs with .0002" tolerance that were far easier to run (on other grinders), thanks to the quality of the machine. Yeah, the coolant sucked in that machine, too.
As I mentioned, above, there's the problem of holding things that have cuts taken beyond reason. Having specialized in small work (my shop was titled Micro-Precision Mfg.), I'm all too aware of the problems of wheels kicking parts off a surface grinder. It's a different world for folks that aren' t working with large surface areas that are held firmly. You're "one size fits all" message is going to get some of these guys in trouble.
For me, two reasons. Safety, and wheel life/work quality . And I wouldn't use .005" passes, I'd use nearer .010", but most importantly, I'd leave the proper amount for grinding. I never put myself in the position where I needed to remove excessive amounts of metal in finishing, not even with a centerless, which is nothing short of a metal hog. It makes no sense, and isn't necessary. No way in hell would I leave .05", not if I had any control over the project. Regardless of your claims, there's no way in hell you can rough by grinding as fast as you can machine, not when using typical shop machinery. I'd substitute skill and experience for excessive material. It's always worked for me, so I have had no need for unreasonable depths of grind. :-) Maybe that's why I disagree with cuts like you're suggesting. They're not necessary!
You're absolutly right on this point. If you're moving serious metal, you better have a serious hold on your part.
Don't forget, I qualified my statement. I was talking about 50+ RC steel before the days of common high quality carbides. I couldn't match the metal removal rates of today's milling equipment in soft steel, not even close.
Depending on the complexity of the part, and the type of material it was sometimes necessary to leave quiet a bit of stock. A thin rib in H-13 for example had a nasty habit of moving around during heat treat. For cavity blocks with deep pockets, the material would often move over .020". If you wanted the part to be right, you better have something left to clean up.
Man, can I sympathize with that! Every now and again something bites you on the ass. Long heat treated pieces in a centerless grinder can be a nightmare for that very reason.
Been fun comparing notes with you-----you obviously have some damned good experience behind you. As much tooling as I've done, and it's been a lot, I've done almost no mold work. I have never claimed to be a die maker. I've learned a little just talking.
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