What are they good for? I just don't get it although I've done my homework and have even consulted wikipedia, that ultimate authority! I understand they will grind down a surface in infinitessimally small increments and produce a beautiful surface. But on what? And why? V
Most of their commercial use is in the tool and die industry, where they're used to make extremely flat surfaces, to extremely accurate dimensions. It's also possible to use a shaped wheel to cut 2D contours and grooves. Multi-piece blanking dies are sometimes made from sections ground on surface grinders, with several pieces making up a complete internally contoured shape. With special fixtures, they can be used to cut complex shapes like those on cutting tools.
The materials they cut in those applications are mostly hardened tool steels of all types. But they can be used on anything you'd care to grind. With diamond wheels, you can cut carbide and ceramics.
It's not a primary home-shop tool but they're darned handy, if you can get one for a reasonable price that's in good condition. Their bedways (generally roller type) are protected against grinding grit but the way covers and other protective devices may be shot on an old one, in which case the ways can be in very bad shape.
It's a high-class end of metalworking manufacturing. The term is a broad one that includes all of the production tooling made for high-volume metal stamping and blanking, bending and forming, forging, die casting, and (the biggest part of it these days) moldmaking, which is the making of plastic injection molds. These tools are made mostly of exotic alloy steels, hardened, or sometimes of tungsten carbide. A die set for making some high-volume product can cost upwards of $100,000. For stamping car body parts, the tools can cost many times that much. When a car model changes and the panel is no longer used, the tool is scrapped.
Surface grinders are used to square up those blocks of steel on the smaller tools, which is the primary part of the business, and to grind various features on the tools. Some of their functions have been replaced by hard milling and electrical discharge machining (EDM), and there are other types of grinders, such as CNC profile grinders, that replace some work that was once done on surface grinders. But surface grinders are still essential machine tools in any tool, die, or mold shop.
FWIW, some custom gages for measuring manufactured parts are also made in those shops -- a specialized type of t&d shop, usually, called a gage shop. Custom gage making is considered to be a part of the tool-and-die business. ("Gauge" is usually spelled "gage" in this business, when it applies to a tool made for measurement.) A part of the t&d business that used to be one of the largest, making jigs for drilling and fixtures for production milling, has declined sharply with the advent of CNC.
Toolmaking often requires accuracies measured in millionths of an inch. It requires specialized training for commercial work. If you added up the output of all of the tool-and-die shops in the United States, it would barely make it to the Fortune 500. But it's the cornerstone of manufacturing, having a huge leverage effect on the manufacturing industry.
The Chinese are still not very good at it, with a few exceptions. d8-)
I cant be as techo as some of the others, who gave a good tutorial. What I know about them was learnt in class by using them, three applications ( practical) come to mind.
1.For squaring off a V-block , this was made using the horizontal and vertical mill, and then finished to tolerance with the surface grinder. Final accuracy of the V block was checked against a master square.
2.Another application was grinding a piece of steel plate flat and true - this was to be able to check the head setup on a Bridgport milling machine using a finger gauge. Any surface irregularities of the plate would have stuffed up the test reading.
3.A variation is the cylindrical grinder - I turned a MT2 taper in the lathe, 0.5mm oversize. This will be put onto the cylindrical grinder and ground to final tolerance - which can be 1 micron, all going well.
AND - they give a BEAUTIFUL surface finish to your job.
so. There. I want one. But its not likely. (Wanna better lathe, and mill, and lotsa tooling...)
A good one will grind a mirrorlike finish to micron accuracy and flatness.
Mine leaves visible ripples and might reach 0.0002" parallelism across a small part on a good day, which is still far better than my 50 year old milling machine can do. I use it rather than a belt sander to clean up milled surfaces, and to smooth and square the three reference faces on a block of annealed scrap steel before carving the part out of it.
It's most recent task was to flatten the inboard end of a chainsaw bar to try to fix an oil leak. Before that I used it to un-warp the head of an old air compressor, taking light cuts off alternate sides until it would sit flat on the chuck without rocking. Both parts were thin and flexible and would be difficult to clamp down on a mill but easy on the magnetic chuck.
I can't argue that they are really necessary in a home shop but if you find a small one at a good price they are quite useful for sharpening end mills etc and smoothing mild and hardened steel surfaces without rounding the edges like a belt sander. Unlike a mill they don't care how hard the steel is and the mag chuck lets you cut the entire top of a thin part, like a shim washer that would be tricky to machine any other way.
I don't know about woodworking and metals, but we often use grinders in my ceramics class. When the glaze runs down in the kiln, it sticks to the bottom, which causes the piece to be seriously off balance. We often use the grinders to create a smooth, even surface. - Student
What I've been using my 8"x24" one for this year is:-
Grinding the widths of hardened gears to exact size to fit between the guides in a gearbox.
Grinding the covers and frame of said gearbox flat to get an oiltight seal.
Grinding a lathe bed flat.
Grinding all faces on some 30-60 degree squares. to mount said bed on to grind the dovetails on it back to shape.
(with the help of a spin indexer and collet) grinding some of the shank of a reamer down so that I could ream to the end of a long hole.
Grinding accurate thread and gear cutting lathe and shaper tools.
Making parallels for the shaper.
Squaring up and equalizing the sizes of components for a sine table.
Materials handled have varied from 12L14 type to hardened 4340 to cast iron to HRS rubbish.
Surface grinders are like any other machine tool. No imaginable applications for one until you've got one. Once you've got one it sits there saying "please let me do that job" to you every time you walk past it.
All the surface grinders I can recall using had coolant. Matter of fact, where I went though my apprenticeship, only the mud produced by a grinding machine was "swarf." Pretty much any other machine made "chips."
My little Sanford 4x8" surface grinder does not have coolant. It has an electro-magnetic chuck, powered from circuitry in the base, and the manual warns to *not* use coolant with the electro-magnetic chuck.
The circuitry in the base does not include a transformer to isolate the power line from the chuck, so I tend to agree with the "no coolant" rule for that machine.
I think that the more general meaning applied to "swarf" came from those in the UK.
I've seen the effects of a Harrig 618 placed too close to a lathe. Grinder was always run with coolant but an astonishing amount of abrasive crud made its way to the lathe. Sure made me feel sick to see that nice Leblonde being treated that way. During my nightly walk around, I wiped the lathe down to help save it.
It and and the rest of the machine tools were moved a while back to another area of the shop, much better layout, maybe the lathe will live a long life now.
Both places I specifically worked in precision grinding, the grind shops were set off. At PNSY, the small machines were enclosed in their own four walls and the big grinders and hones were pretty much together out on the floor bounded by aisles. At NADEP, the grind shop was just segregated to its own section of the machine shop by aisles. Every production grinding machine in both shops ran coolant (or oil). Only the tool and cutter grinders (also in their own section) ever ground anything dry... and they all had a hose from the central vacuum.