Since crankshaft grinding wheels are extremely hard and abrasive, a special tool is required to dress the wheel. This tool, which is commonly called the wheel dresser, utilizes an industrial diamond for cutting the wheel’s stone. Not surprisingly, there are various sizes of diamonds that are used and categorized according to their carat weight.

When dressing any crankshaft grinding wheel, it is important that the diamond be set between ten and fifteen degrees of the surface being dressed. Also, coolant must be used on the diamond at all times during the dressing process. This will help to extend the life of the industrial diamond and aids in producing a quality finish on crankshaft journals.

A crankshaft grinding wheel dresser is capable of dressing all five surface points on the grinding wheel. The dresser also has a slide gauge on it to set the diamond for dressing the radii and a pivoting head so that the machinist can accurately replicate the desired radius that is being cut into the wheel. Most wheel dressers use quick releases to make the task of dressing a crankshaft grinding wheel even easier for the operator.

The first step in dressing a crankshaft grinding wheel involves setting a zero or home point. To accomplish this, the diamond is set in the gauge for the appropriate radius by using the sliding scale. The operator then secures the swing head so that the potential for vibration is eliminated and the machine’s coolant is turned on to cool the diamond as it comes into contact with the wheel. The face of the wheel can now be dressed. Once the face is dressed, the machine’s plunge feed dial is set to zero. The wheel dresser is now appropriately set and the radii is ready to be dressed.

With the dresser safely away from the spinning grinding wheel, the operator may now release the swing head on the wheel dresser and secure it in a ninety degree position to cut the first radius. Once secured, the operator brings the diamond slowly into the side of the wheel (horizontally) until it just barely touches. Once the industrial diamond touches the grinding wheel, the plunge feed on the machine is backed off around one hundred thousandths of an inch. The operator may now slowly move the diamond from a ninety degree position back to its stop, which is in line with the face of the wheel. The operator will then bring the plunge feed in even closer to zero, while taking sweeps with the swing head on the dresser as to avoid a heavy cut that could potentially damage the industrial diamond. Once within a few thousandths of zero on the plunge feed, the operator may then replicate the same process on the other side of the wheel to attain a consistent radius on both sides.

To dress the side of the wheel, which is needed to grind crankshaft thrusts, the diamond is often removed from the dressing fixture and placed in a position that allows the operator to perform dressing operations in a fixed ninety degree position. The operator will secure the dressing tool and bring in the grinding wheel using the power feed. Manual adjustments by the operator may be necessary to dress the section of the wheel that is used to grind thrusts. Once this position has been found, the operator will slowly bring the diamond into the side of the wheel, turn the coolant on and feed the diamond into the wheel about .005”. The power feed is then used to take the grinding wheel back to its home position and results in the initial cut. The wheel then may be power fed back in, diamond adjusted and an additional cut taken. This process is replicated on the other side of the crankshaft grinding wheel to maintain a consistent surface for grinding the thrusts on crankshafts.

The reason why a crankshaft grinding wheel may need to be dressed is because the stone eventually gets loaded with material. Loading in the wheel may be increased if the operator takes heavy cuts when grinding crankshafts or from roughing in a welded crankshaft. Also newly balanced wheels must be dressed before they are put into service. Under typical grinding conditions, a wheel will ordinarily remain sharp and last long enough to grind three or four crankshafts. Welded journals, on the other hand, will dull a crankshaft grinding wheel rather quickly and must be dressed before a finish grind is performed.

As with any machining operation, the speed at which a wheel is dressed will help to determine the quality of the microfinish it produces. For example, dressing with a fast feed often results in a stone that would produce a rough finish. Although a rough finish is not desired on finished crankshafts, it can be rather useful when roughing in welded journals. If the operator has multiple welded journals to grind, or possibly an under-grinding process in preparation for a weld, a rough finish is actually helpful. Regardless of the desired microfinish, the rate at which the operator feeds the stone should always remain as humanly steady as possible to maintain consistency across the cutting surface.

Now that you have learned how crankshaft grinding wheel dressers work, and how they help to produce journals of a precise size and microfinish, please consider rating this information below.

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Apart from a micrometer, one of the most important measuring instruments an automotive machinist uses when he or she grinds a crankshaft is an Arnold gauge. Unlike any other device, the Arnold gauge allows the operator of a crankshaft grinding machine to precisely read how much material is being taken off of the journal in real time. This ability, to see how much material is being ground off of a journal, allows the operator to grind crankshafts to extremely close tolerances.

The Arnold gauge, which is pictured left, is not only used in automotive machine shops. Many different industries, such as those involved with manufacturing aerospace and aviation components, rely on an Arnold gauge for a variety of O.D. grinding operations. With an accuracy of .0001”, it is quite easy to see why so many machinists are pleased with how well this gauge performs. Besides being accurate, an Arnold Gauge is also very easy for an operator to use.

Being attached to the crankshaft grinding machine, with a spring loaded support arm, allows a crankshaft grinding machine operator to effortlessly attach the gauge on and off of a journal at will. The entire gauge assembly includes a precision dial indicator, durable frame and an adjustable caliper. In most cases, the operator will use a standard caliper that adjusts from 1” to 3” in diameter. This is sufficient for grinding most passenger car and light truck crankshafts. For industrial crankshafts, which tend to have large journals, the caliper can be easily changed to accommodate a journal that is up to 12” in diameter. In the video below, you can view an automotive machinist using his Arnold gauge while grinding a crankshaft.

In the video you will notice just how easy the Arnold gauge can be used. When it is attached to the journal being ground, two round tungsten carbide contact points allow it to ride on the journal and a plunger on top takes the measurements. Although the plunger spring tension can be adjusted, it is not uncommon for these gauges to work well for many years and without the need of factory calibration. However, operator errors can occur that may damage an Arnold gauge.

One of the greatest hazards the Arnold gauge can come into contact with is an oil passage on the crankshaft’s journal. With the gauge riding on three points, including the plunger, any one of these contact points can ride over and into an oil passage. Even the most experienced machinist will have the occasional mishap and catch part of an oil passage, especially when the steady rest is also riding on a very narrow V6 rod journal. Thankfully this gauge is quite durable and can handle minor mishaps. Crankshaft counterweights, on the other hand, can actually catch the side of this gauge and pull it into the journal; thus causing major damage to not only the Arnold gauge, but to the crankshaft being ground and possibly the machine as well. Therefore, an operator must always be alert when using the gauge to measure the material being ground off of a crankshaft.

The Arnold gauge is a standard measuring device used by most within the automotive machining industry to repair crankshafts. These gauges are found on Berco, RMC, Storm Vulcan, Winona Van Norman and many other crankshaft grinding machines throughout the world.

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When grinding the rod journals, a steady rest is typically positioned to the side of the oil passage and tightened down to the grinding machine’s ways. Since the shoes ride directly on a journal, they must avoid the oil passage as a shoe may be drawn into the hole and damage the crankshaft and/or the equipment being used. Also, there must be adequate room for the operator to use the Arnold gauge to measure the amount of material being ground off. Especially on V6 crankshafts, where there is little side to side clearance, placing tooling and measuring devices on the journal at the same time can be quite a challenge. Once properly positioned, safely to the side of any oil passages and with plenty of room for the Arnold gauge, the automotive machinist then slowly tightens up the steady rest so that it supports the journal as it is being ground. As the machinist takes off more material, the arms are slowly tightened even more so that shoes remain snug to the journal throughout the entire grinding process. The steady rest is the one tool that resists the force created from the grinding wheel as it is slowly fed into the journal, which is an important function to produce finished journals of the proper size and microfinish.

Once the first connecting rod journal has been ground, the steady rest can then be used to index over to the next rod throw. This is accomplished by locking the steady rest in position for the next rod journal and then indexing the journal over to the steady rest’s upper shoe until it stops. This will normally result in a journal that is within .010” of the position it needs to be in for grinding. Modern steady rests include dial indicators on them so that the machine’s operator can make minor adjustments to the crankshaft’s stroke and side to side positioning. After releasing the chucks for positioning, the operator will utilize a stroke gauge to make minor modifications to the stroke and adjust the side to side positioning by turning large industrial wing nuts.

In addition to supporting the crankshaft journal during the grinding process, a steady rest also doubles as a shield to protect the operator from coolant splashing on him or her. Additional shields then may interlock on both sides of this device to provide complete coolant containment and protection for the operator. You can see a picture of a steady rest in use, with the splash guards in place, by viewing the image to your right. Please note that the journal being ground in this image is a main journal on a two cylinder crankshaft.

The steady rest is typically used in a fixed position when grinding the crankshaft’s main journals. The reason for this is to provide support at the center of the crankshaft since the snout is supported in the headstock and the rear flange is supported in the tailstock. In most cases, the center journal will be ground first so that the secure steady rest’s shoes will have a true journal to support grinding the remainder of the mains. This allows all of the crankshaft’s main journals to be true and properly aligned with each other and the seal surface of the crankshaft.

If a steady rest is not properly secured on a journal while it is being ground, the journal will be out of round. It’s not uncommon for a journal to be .0005” out of round when the steady rest has not been used to properly support a ground journal. Even when used properly, the journal may still be out of round by .0002” as it nears its finish size. A good automotive machinist will see this out of round condition on the Arnold gauge and gently bump the top top steady rest dial, with his or her thumbs, to force the grinding wheel to take off more material on the high side of the journal.

Even with a welded crankshaft, where the journal is still rough, the steady rest is still used. However, the steady rest’s arms are not tightened so that the shoes do not come into contact with a rough surface. Instead, the steady rest is used to protect the operator from potential grinding debris and coolant splashes. Once the welded journal has a smooth surface, then the operator can tighten the steady rest to support the journal with its shoes.

When a crankshaft journal has been ground, there is often a slight mark left on the journal from the upper and lower steady rest shoes. These shoes, like the steady rest shoe pictured to the left, are made out of a special material that is comparable to a very thick and hard rubber. The shoes are non-abrasive, but do leave a slight amount of material on crankshaft journals that can be easily wiped off or polished out. When the shoes eventually wear out, they may be easily replaced and are actually quite inexpensive. Regardless, a new set of shoes will have a duty cycle that will give automotive machine shops the ability to grind hundreds of crankshafts. This duty cycle is a testament to the quality and durability of these important components.

The primary purpose of a steady rest is to support the journal during the grinding process. This gives the automotive machinist the proper tooling to avoid not just out of round conditions, but also chatter. Chatter can occur when the crankshaft grinding wheel comes into contact with a radius or counterweight. Additionally, an improperly dressed grinding wheel also demonstrates a heightened level of deflection and may produce undesirable chatter on the journals. With the correct tooling in place to support the journals, the operator is better equipped to produce a reconditioned crankshaft that is within proper specifications.

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