There are many factors to consider when choosing the right grinding wheel.
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According to Modern Machine Shop:
&#;The grinding wheel is a cutting tool. It&#;s an abrasive cutting tool.
&#;In a grinding wheel, the abrasive performs the same function as the teeth in a saw. But unlike a saw, which has teeth only on its edge, the grinding wheel has abrasive grains distributed throughout the wheel. Thousands of these hard, tough grains move against the workpiece to cut away tiny chips of material.
&#;Abrasive suppliers offer a wide array of products for a wide array of grinding applications in metalworking. Choosing the wrong product can cost the shop time and money. This article presents some of the fundamentals of selecting the best grinding wheel for the job.
Abrasives&#;Grits and Grains
&#;Grinding wheels and other bonded abrasives have two major components-the abrasive grains that do the actual cutting and the bond that holds the grains together and supports them while they cut. The percentages of grain and bond and their spacing in the wheel determine the wheel&#;s structure.
&#;The particular abrasive used in a wheel is chosen based on the way it will interact with the work material. The ideal abrasive has the ability to stay sharp with minimal point dulling. When dulling begins, the abrasive fractures, creating new cutting points.
&#;Each abrasive type is unique with distinct properties for hardness, strength, fracture toughness and resistance to impact.
&#;Aluminum oxide is the most common abrasive used in grinding wheels. It is usually the abrasive chosen for grinding carbon steel, alloy steel, high speed steel, annealed malleable iron, wrought iron, and bronzes and similar metals. There are many different types of aluminum oxide abrasives, each specially made and blended for particular types of grinding jobs. Each abrasive type carries its own designation-usually a combination of a letter and a number. These designations vary by manufacturer.
&#;Zirconia alumina is another family of abrasives, each one made from a different percentage of aluminum oxide and zirconium oxide. The combination results in a tough, durable abrasive that works well in rough grinding applications, such as cut-off operations, on a broad range of steels and steel alloys. As with aluminum oxide, there are several different types of zirconia alumina from which to choose.
&#;Silicon carbide is an abrasive used for grinding gray iron, chilled iron, brass, soft bronze and aluminum, as well as stone, rubber and other non-ferrous materials.
&#;Ceramic aluminum oxide is the newest major development in abrasives. This is a high-purity grain manufactured in a gel sintering process. The result is an abrasive with the ability to fracture at a controlled rate at the sub-micron level, constantly creating thousands of new cutting points. This abrasive is exceptionally hard and strong. It is primarily used for precision grinding in demanding applications on steels and alloys that are the most difficult to grind. The abrasive is normally blended in various percentages with other abrasives to optimize its performance for different applications and materials.
&#;Once the grain is known, the next question relates to grit size. Every grinding wheel has a number designating this characteristic. Grit size is the size of individual abrasive grains in the wheel. It corresponds to the number of openings per linear inch in the final screen size used to size the grain. In other words, higher numbers translate to smaller openings in the screen the grains pass through. Lower numbers (such as 10, 16 or 24) denote a wheel with coarse grain. The coarser the grain, the larger the size of the material removed. Coarse grains are used for rapid stock removal where finish is not important. Higher numbers (such as 70, 100 and 180) are fine grit wheels. They are suitable for imparting fine finishes, for small areas of contact, and for use with hard, brittle materials.
Buying Bonds
&#;To allow the abrasive in the wheel to cut efficiently, the wheel must contain the proper bond. The bond is the material that holds the abrasive grains together so they can cut effectively. The bond must also wear away as the abrasive grains wear and are expelled so new sharp grains are exposed.
&#;There are three principal types of bonds used in conventional grinding wheels. Each type is capable of giving distinct characteristics to the grinding action of the wheel. The type of bond selected depends on such factors as the wheel operating speed, the type of grinding operation, the precision required and the material to be ground.
&#;Most grinding wheels are made with vitrified bonds, which consist of a mixture of carefully selected clays. At the high temperatures produced in the kilns where grinding wheels are made, the clays and the abrasive grain fuse into a molten glass condition. During cooling, the glass forms a span that attaches each grain to its neighbor and supports the grains while they grind.
&#;Grinding wheels made with vitrified bonds are very rigid, strong and porous. They remove stock material at high rates and grind to precise requirements. They are not affected by water, acid, oils or variations in temperature.
&#;Vitrified bonds are very hard, but at the same time they are brittle like glass. They are broken down by the pressure of grinding.
&#;Some bonds are made of organic substances. These bonds soften under the heat of grinding. The most common organic bond type is the resinoid bond, which is made from synthetic resin. Wheels with resinoid bonds are good choices for applications that require rapid stock removal, as well as those where better finishes are needed. They are designed to operate at higher speeds, and they are often used for wheels in fabrication shops, foundries, billet shops, and for saw sharpening and gumming.
&#;Another type of organic bond is rubber. Wheels made with rubber bonds offer a smooth grinding action. Rubber bonds are often found in wheels used where a high quality of finish is required, such as ball bearing and roller bearing races. They are also frequently used for cut-off wheels where burr and burn must be held to a minimum.
&#;The strength of a bond is designated in the grade of the grinding wheel. The bond is said to have a hard grade if the spans between each abrasive grain are very strong and retain the grains well against the grinding forces tending to pry them loose. A wheel is said to have a soft grade if only a small force is needed to release the grains. It is the relative amount of bond in the wheel that determines its grade or hardness.
&#;Hard grade wheels are used for longer wheel life, for jobs on high-horsepower machines, and for jobs with small or narrow areas of contact. Soft grade wheels are used for rapid stock removal, for jobs with large areas of contact, and for hard materials such as tool steels and carbides.
Wheel Shapes
&#;The wheel itself comes in a variety of shapes. The product typically pictured when one thinks of a grinding wheel is the straight wheel. The grinding face&#;the part of the wheel that addresses the work&#;is on the periphery of a straight wheel. A common variation of the straight wheel design is the recessed wheel, so called because the center of the wheel is recessed to allow it to fit on a machine spindle flange assembly.
&#;On some wheels, the cutting face is on the side of the wheel. These wheels are usually named for their distinctive shapes, as in cylinder wheels, cup wheels and dish wheels. Sometimes bonded abrasive sections of various shapes are assembled to form a continuous or intermittent side grinding wheel. These products are called segments. Wheels with cutting faces on their sides are often used to grind the teeth of cutting tools and other hard-to-reach surfaces.
&#;Mounted wheels are small grinding wheels with special shapes, such as cones or plugs, that are permanently mounted on a steel mandrel. They are used for a variety of off-hand and precision internal grinding jobs.
Tying It All Together
&#;A number of factors must be considered in order to select the best grinding wheel for the job at hand. The first consideration is the material to be ground. This determines the kind of abrasive you will need in the wheel. For example, aluminum oxide or zirconia alumina should be used for grinding steels and steel alloys. For grinding cast iron, non-ferrous metals and non-metallic materials, select a silicon carbide abrasive.
&#;Hard, brittle materials generally require a wheel with a fine grit size and a softer grade. Hard materials resist the penetration of abrasive grains and cause them to dull quickly. Therefore, the combination of finer grit and softer grade lets abrasive grains break away as they become dull, exposing fresh, sharp cutting points. On the other hand, wheels with the coarse grit and hard grade should be chosen for materials that are soft, ductile and easily penetrated.
&#;The amount of stock to be removed is also a consideration. Coarser grits give rapid stock removal since they are capable of greater penetration and heavier cuts. However, if the work material is hard to penetrate, a slightly finer grit wheel will cut faster since there are more cutting points to do the work.
&#;Wheels with vitrified bonds provide fast cutting. Resin, rubber or shellac bonds should be chosen if a smaller amount of stock is to be removed, or if the finish requirements are higher.
&#;Another factor that affects the choice of wheel bond is the wheel speed in operation. Usually vitrified wheels are used at speeds less than 6,500 surface feet per minute. At higher speeds, the vitrified bond may break. Organic bond wheels are generally the choice between 6,500 and 9,500 surface feet per minute. Working at higher speeds usually requires specially designed wheels for high speed grinding.
&#;In any case, do not exceed the safe operating speed shown on the wheel or its blotter. This might be specified in either rpm or sfm.
&#;The next factor to consider is the area of grinding contact between the wheel and the workpiece. For a broad area of contact, use a wheel with coarser grit and softer grade. This ensures a free, cool cutting action under the heavier load imposed by the size of the surface to be ground. Smaller areas of grinding contact require wheels with finer grits and harder grades to withstand the greater unit pressure.
&#;Next, consider the severity of the grinding action. This is defined as the pressure under which the grinding wheel and the workpiece are brought and held together. Some abrasives have been designed to withstand severe grinding conditions when grinding steel and steel alloys.
&#;Grinding machine horsepower must also be considered. In general, harder grade wheels should be used on machines with higher horsepower. If horsepower is less than wheel diameter, a softer grade wheel should be used. If horsepower is greater than wheel diameter, choose a harder grade wheel.
Care And Feeding
&#;Grinding wheels must be handled, mounted and used with the right amount of precaution and protection.
&#;They should always be stored so they are protected from banging and gouging. The storage room should not be subjected to extreme variations in temperature and humidity because these can damage the bonds in some wheels.
&#;Immediately after unpacking, all new wheels should be closely inspected to be sure they have not been damaged in transit. All used wheels returned to the storage room should also be inspected.
&#;Wheels should be handled carefully to avoid dropping and bumping, since this may lead to damage or cracks. Wheels should be carried to the job, not rolled. If the wheel is too heavy to be carried safely by hand, use a hand truck, wagon or forklift truck with cushioning provided to avoid damage.
&#;Before mounting a vitrified wheel, ring test it as explained in the American National Standards Institute&#;s B7.1 Safety Code for the Use, Care and Protection of Grinding Wheels. The ring test is designed to detect any cracks in a wheel. Never use a cracked wheel.
&#;A wise precaution is to be sure the spindle rpm of the machine you&#;re using doesn&#;t exceed the maximum safe speed of the grinding wheel.
&#;Always use a wheel with a center hole size that fits snugly yet freely on the spindle without forcing it. Never attempt to alter the center hole. Use a matched pair of clean, recessed flanges at least one-third the diameter of the wheel. Flange bearing surfaces must be flat and free of any burrs or dirt buildup.
For more information, please visit stone grinding tools manufacturer.
&#;Tighten the spindle nut only enough to hold the wheel firmly without over-tightening. If mounting a directional wheel, look for the arrow marked on the wheel itself and be sure it points in the direction of spindle rotation.
&#;Always make sure that all wheel and machine guards are in place, and that all covers are tightly closed before operating the machine. After the wheel is securely mounted and the guards are in place, turn on the machine, step back out of the way and let it run for at least one minute at operating speed before starting to grind.
&#;Grind only on the face of a straight wheel. Grind only on the side of a cylinder, cup or segment wheel. Make grinding contact gently, without bumping or gouging. Never force grinding so that the motor slows noticeably or the work gets hot. The machine ampmeter can be a good indicator of correct performance.
&#;If a wheel breaks during use, make a careful inspection of the machine to be sure that protective hoods and guards have not been damaged. Also, check the flanges, spindle and mounting nuts to be sure they are not bent, sprung or otherwise damaged.
System Analysis
&#;The grinding wheel is one component in an engineered system consisting of wheel, machine tool, work material and operational factors. Each factor affects all the others. Accordingly, the shop that wants to optimize grinding performance will choose the grinding wheel best suited to all of these other components of the process.&#;
Original Source
The seat grinder is hiding in the cabinet. My question is - if anyone on here has ground seats in their AC engines before, what type of stone were you using? I am currently planning on ordering some general rough and finish stones since I can't find that AC was using anything like Stellite in the WD-45 and earlier tractors, which is mostly what I have. Figured someone on here might have some experience with what the best types of stones to use are.
I bought an old Sioux 645L valve grinder/refacer a couple years back, tore it apart to clean it up, and didn't get it put back together until the other day. My WD needs some touch up work on the valves and seats (it appears to have seat inserts installed already).
B, B, WC, WD, CA, WD-45
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They might have information about this for you.
Regards,
Chris
I would call Bill at Sandy Lake.
John,
D17 (NFE), WD45 (NFE), WD (NFE), WD (WFE), Allis F-40 forklift, Allis CA, Allis D14, Ford Jubilee, Many IH Cub Cadets, 32 Ford Dump, 65 Comet.
Last time I did that they were in the head. Bought some abrasive paste stuff and a valve grinding tool and just went down the line. They looked good to me.
D14, D17, , 612H, CASE 446
You can buy wheels of different DIAMETER to fit into the SEAT, so check that... and you can buy them different ANGLES to get the top cut and bottom cut on the SEAT... so verify that.
john, they have course, medium and fine wheels, just like the paste you use to lap them in to finish... The GRIT you use to CUT the seats or valve faces depends on how BAD they are to start with... Normally you can use a medium or fine wheel and just take a couple thousandths off to true them up.... You do something like cut the valve faces at 45 degrees, then cut the seats in the head at 44 and 46 so you have a line in the center where the valve seats... then you lap it in to get the width of the seal you want... maybe .060 or so... Every engine spec is different, but basically they are all the same.
Like them all, but love the "B"s.
Exactly what Steve said and I might add that when you grind the seats you&#;ll know real quick if you need to use a coarse stone. I used a fine stone to start then went aggressively if needed. Not sure about AC but if you hit a soft seat with a finish stone it will clean it right quick if it&#;s a hard seat you&#;d be there for ever.
Also that Souix should have a degree mark that is 1 off the (ex 45) degree on both the seat stone cutter and on the valve grinder angle.
"LET"S GO BRANDON!!"
I'll order general purpose rough and finish stones, and get some to cut at 60 or 30 degrees to narrow the seat width if needed. The intake seats look like I can just touch them with the finish stone but I may have to use the rough stone on one or two of the exhaust seats.
Thanks for the tips guys. I was reading that seats that are just cut into the cast iron of the head should grind easily with just a finish stone. I have all the manuals for my Sioux stuff and it does a pretty good job of explaining things and calling out stones for specific engines, but with seat inserts installed (presumably harder than the factory seats in the cast iron of the head) they're a bit of an unknown. I do at least have the right stone diameters from that Sioux chart. There are several stone materials now (one for Stellite, one that's ruby, another that's cool blue, etc.) beyond the general purpose rough and finish so I didn't know if anyone had any preferences.
B, B, WC, WD, CA, WD-45
Kansas99 wrote:Yep, the seat grinder dresser has a 46 degree mark to cut the stones at and the chuck for the valve grinder has a 44 degree mark (and probably the same 1 degree off for 30 degree valves, but I don't have anything with 30 degree valves that I'm aware of so I haven't paid attention). The AC manual just specs 45 degrees for everything while some of my other engine manuals spec the 1 degree interference fit. I may tweak the seats and valves +0.5 and -0.5 degrees just so I'm erring on the "safe" side with tolerances of 45 degrees for both of them.
It'll be a learning experience either way but I figured it's something I should be able to do in house for most of my older engines. New valves are cheap for some engines and not so much for others, and a lot of times the seats aren't so far gone that they need to be replaced.
B, B, WC, WD, CA, WD-45
look up goodson, they have all kinds of valve grinding stones, and accessories. I prefer the white stones for stellite, since they seem to be backward compatibly, so they will work ok on everything you may encounter. The trick is getting the sizes you need that fit right.
210 "too hot to farm" puller, part of the "insane pumpkin posse". Owner of Guenther Heritage Diesel, specializing in fuel injection systems on heritage era tractors. stock rebuilds to all out pullers!
Thanks Ed. This time I am going with Woodward/Cylinder Head Supply but did find Goodson, Regis, and Beam Equipment - all seem to be great sources of valve/seat grinding parts. I think it's amazing that these companies are keeping these machines going after Snap-On bought Sioux, shut them down, and abandoned service support.
B, B, WC, WD, CA, WD-45
Christmas in May? My grinding stones, fluid, etc. order came in. Guess I better get the valve guides ordered so I can do the seats.
B, B, WC, WD, CA, WD-45
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