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Quite simply, this product will enhance roll setup technology by improving antiquated methods for  establishing, checking, and maintaining alignment of the roll centerline to the headstock center of rotation on virtually any roll grinder.  Implementing this gaging system concept should improve the grinding accuracy, since it will be much easier for the operators to check and correct the roll alignment than is normally the case.  In addition, chatter and pattern problems will be encounter less frequently, which quite often are the result of a severe misalignment between the roll centerline and the true center of rotation.


This has been an area of concern when troubleshooting grinding problems for a number of years now.  Many vibration and machine inspection reports include references to the headstock roll driver once or twice per revolution knock.  This causes a heavy thump that transfers throughout the machine, and can precipitate chatter and pattern conditions, as well as the “flash” problem sometimes seen on rolls ground eccentric to the headstock driver.  The photo on the right, taken during an inspection of a typical Farrel grinder, shows the results of severe misalignment on the pivot bearing shaft.  Note the evidence of “chatter” marks around the circumference, which were obviously caused by an extreme condition, resulting in excessive movement of the pivot mechanism, and abnormally high stresses on the supporting elements.

With regard to roll centering, it is important to recognize the differences between “roll grinding”, as opposed to a conventional cylindrical grinder or lathe type application.  These machines generally support the roll on live or dead centers, with steady rests used as auxiliary support only, so the roll is always on true center.  This is not the case with a roll grinder, which utilizes Babbitt lined gib blocks for support of the roll on the journals only.  Since the Babbitt is continuously wearing, the roll centerline is constantly dropping.  In addition, wear of the side gibs results in operator adjustments to maintain taper tolerance, which generally moves the roll centerline toward the wheel (due to backlash in the adjusting screw, the adjustment is usually made in this direction).  The net result of the bottom and side gib Babbitt wear is an increasing offset between the roll centerline and the true headstock center of rotation.  The severity of the problem is a function of the number of rolls ground, headstock speed, grinding loads, journal lubrication, Babbitt specs, etc.

Typically, the Farrel headstock equalizer is designed to compensate for not more than .100” of misalignment; however, offsets significantly less than this can have detrimental effects on roll geometry and finish.  Therefore, it is in the best interest to institute a program that will insure roll misalignment never exceeds acceptable limits.

Conventional Methods of Control

Generally, there are two methods used to center the rolls to the headstock rotation.

1. The more common approach is to retract the neckrest bottom and side gibs, mount the roll on the headstock and tailstock centers, and then readjust all the gibs with the roll supported on the dead centers.

2. Another method is to use a long stem dial indicator mounted on the headstock faceplate reading against the roll neck.  The headstock is rotated slowly (the drive collar can be left on if there is a keyway in the journal), and the TIR is measured in the vertical and horizontal planes.  The sketch and photo on the right shows this setup.  The headstock end bottom and side gibs are adjusted until the TIR is close to zero.  Then another dial indicator is used to tram along the top of the roll as the carriage is traversed from one end to the other, and the tailstock bottom and side gibs are adjusted accordingly.

There are a number of problems with method #1:

a) The roll centers are usually not machined concentric to the roll journals; in addition, they are often worn, pitted, and sometimes badly abused.

b) If the thrust force is not adequate, the weight of the roll makes it difficult to achieve a good fit in the centers, causing the roll to drop below center.  This can be a real problem with backup rolls in the larger grinders.

c) The angle of the centers does not always match the angle of the center hole in the roll.

d) The tailstock traverse and quill feed may not be operative.  Some grinders have a motorized traverse and quill; some only have manual handwheels.  Usually, the tailstock is not used that often, resulting in binding of the mechanical mechanisms or electrical problems due to lack of use.

e) Sometimes the center points are missing, lost, or damaged.

f) Probably the biggest obstacle to putting the roll on centers is that it requires a major physical effort and time expenditure on the part of grinder operator, as well as occupying overhead crane time. Consequently, they usually find a way to avoid this exercise, and will opt to let the grinder run as long as it can in the misaligned condition.

It is also difficult to get the operators to use the dial indicators to check and correct roll alignment.  The reasons are as follows:

a) They need a long travel indicator with a good magnetic base and a long enough arm to reach the roll neck.  These are usually not readily available.

b) It is difficult to watch the indicator movement as it rotates through 180 degrees.  An additional person is usually required, or mirrors must be used.

c) Since the roll centerline is usually below the headstock centerline (due to the fact that the gib Babbitt has worn), the bottom gib must be raised to bring the roll back on center.  It is very hard to turn the gib adjusting screw with the weight of the roll on the stands, especially backup rolls.

d) The process is time consuming since a number of dial indicator checks are required in two planes to get the roll on center.

e) Some of the operators don’t understand the technique, and have trouble reading and setting the indicators; thus, they are reluctant to attempt to try to learn the method.

The above notwithstanding, the dial indicator procedure has proven to be an excellent method to troubleshoot and evaluate the grinder’s alignment condition. Invariably, when making these random checks in a customer’s roll shop, the rolls are found to be significantly out of alignment, sometimes as much as 3/8”!

It should be noted that an Eddy current gage only checks for roll “level”, and cannot measure the absolute position of the roll relative to the headstock rotation.

Mechanical Roll Alignment Gage

In the past, RGB Engineering has promoted a roll alignment gaging system that uses fixtures and lightweight disks that register in pads and pockets machined into the neckrest stands.  This concept has been used in some instances, and still has merit for certain situations.  But the laser approach is a more state of the art solution to the problem, and should be more readily accepted by the operators.

Proposed Laser Alignment System – General Description

The laser alignment system being offered now has the fundamental advantage of simplistic operation, which hopefully will encourage the operators to use it on a regular basis, and maintain good alignment of the roll centerline to the headstock.  The tailstock center is removed, and a laser instrument permanently mounted inside the cavity.  A receiver unit is used to initially “buck” in the laser by registering in the headstock spindle, and then on an ongoing basis to set the proper position of the bottom and side gibs using a ring type fixture.  The laser can also be used in a visual mode without the receiver, by viewing the beam projection directly on the end of the roll, to get a rough idea of the roll position in the grinder.  For more accuracy, a lightweight template with a target grid is supplied.  This can be easily set on the tailstock end of the roll and the beam projection viewed with respect to the grid cross-hairs.

There are many advantages of this gaging system compared to current practices:

a) The procedure is straightforward, simple, and easy for the operators to understand.  Thus, they will be more inclined to keep the rolls lined up.

b) Alignment time should be less than methods “1” and “2” previously described.

c) It is not necessary to hang the rolls on centers.  Therefore, the overhead crane will not be required, freeing it up for other functions.

d) The gib adjustments are made without the roll in the machine, so minimal effort is required to adjust the gibs, and the operators have less physical work to do.

e) Roll centerline position can be easily checked at any time by anyone just by turning on the laser beam.

A five sheet drawing is available upon request that describes the complete assembly:  Sheet I shows the mounting arrangement of the laser head in the tailstock, and sheet 2 shows details of the receiver mounting on the headstock center.  Sheet 3 shows the neckrest receiver setup, and sheet 4 the targets on the roll ends.  Sheet 5 is the parts list.  The actual laser is provided by Pinpoint Laser Systems - details of the Microgage 1000 laser alignment hardware can be accessed at www.pinlaser.com.


Listed below are some general comments, specifications, design highlights, etc., that describe the complete system in more detail.

Laser Mounting Arrangement

As noted above, the center is removed from the tailstock quill exposing the Jarno taper bore.  The referenced drawing shows a Farrel 50” tailstock assembly, but it will also fit a 36”.  An engineering study would be required to determine the feasibility for other makes of grinders, but the likelihood is that similar mounting principles would apply.  A tapered mounting ring registers in the bore at the inboard end, and serves as the fulcrum point for the gimbaled double pivot assembly.  This is simply two needle bearings arranged at 90 degrees to provide a two degree of freedom support of the bracket extension at the inboard end of the tapered bore.  Since the parts are machined concentric to the bore, the centerline of both pivots should be on the true machine centerline at this point.

The laser bolts to the support plate as shown at the proper height with respect to the aforementioned pivots.  Four ¼” tapped holes have to be drilled in the outboard face of the tailstock spindle, which serve as mounting points for the fixture ring.  An end plate, machined for vertical guide keys, is adjusted up and down using set screws in the fixture ring.  Similarly, using set screws in the end plate, the laser mounting plate can be adjusted side-to-side in the horizontal plane.  Once alignment is obtained, the support plate is bolted to the end plate using two ¼” cap screws.  There is an oversize hole in the support plate to allow for horizontal and axial adjustment variation.  Slotted holes are also provided in the rear connection for axial compensation as well.

An end cover, which fits loosely over the fixture ring, serves as protection for the laser parts, and also as a bumper for controlling the roll axial position.  A ball thrust bearing pressed into the end cover serves as the contact point with the roll.  Any thrust forces will be transferred directly through the end cover to the tailstock spindle.

The photo above shows the laser mounting in the tailstock before the end cover was installed.  The photo below shows the actual setup during grinding with the end cover in place.

Normally, the laser is powered by batteries, but for this application, a transformer power-pack is included for a 120 volt supply.  An On-Off switch is provided to turn the laser beam on and off.  The receiver unit is powered by a 9 volt battery.

Initial Alignment Procedure

The vertical and horizontal adjustments are made in conjunction with the receiver unit that is temporarily mounted on the headstock center (see discussion below).  This is a one-time adjustment; once the laser is lined up true to the headstock center, no further adjustments should be required.  However, it is recommended that periodic checks be made, at least initially, to verify that alignment is being maintained, especially if the tailstock is moved.  (Installation checks showed that the alignment accuracy was not significantly affected when the tailstock was moved on the bed approximately six feet.)

Receiver Mounting Arrangement – Headstock Center

The receiver mounts on the headstock center.  A precision ground shaft registers in the headstock spindle tapered bore, and provides a mounting axis for the receiver bracket concentric to the headstock center of rotation.  An adapter bracket slides on the shaft, and serves as a support plate for the receiver unit.  The photo on the left shows this setup.

In the location shown, the receiver will measure the laser beam position in the vertical plane to an accuracy of about .001”.  The attached spirit level is used to orient the bracket assembly in this position. Then the vertical adjustment can be made on the laser as described above. When this is done, the receiver unit is rotated on the shaft exactly ninety degrees. The other spirit level is used to verify the horizontal orientation, and the horizontal adjustment made on the laser mount. A check should be made in the vertical plane to verify alignment.

Receiver Mounting Arrangement – Neckrest

The received can also be mounted on the neckrest gibs.  If it is determined that the roll is significantly off center, then each set of gib blocks in the neckrest stands should be set on true center. This is done using the same receiver unit, but mounted in a different fixture.

The neckrest fixture consists of two lightweight aluminum plates, machined to the exact diameter of the roll necks, fastened together with four tie rods equally spaced as shown.  The receiver unit is bolted to the center tie plate.  The fixture is positioned axially in the approximate center of the gibs, and the spirit level used to orient the round disks in the vertical plane.  The bottom gib is adjusted to bring the readout to zero.  The other spirit level is used to set the fixture at ninety degrees for measuring in the horizontal plane.  The side gib is adjusted to bring the readout to zero.  The vertical plane measurement is repeated, and a final adjustment can be made if required.  The photo above shows the fixture being used on the headstock end neckrest to set up the gibs.  The same procedure is used on the footstock neckrest.  For the larger roll neck on the backup roll, three segment sections are bolted to the base fixture to extend the diameter range.  Wing nuts are used to minimize the changeover time.

Quick Alignment Check

A rough check on the roll alignment can easily be done by simply turning on the laser, and observing the red dot directly on the tailstock end of the roll neck.  The dot should be concentric to the center countersink.  However, contamination and roll damage may affect the accuracy of this reading.  A more accurate check can be made using target fixtures.  These are lightweight aluminum disks designed to fit over the end of the roll neck, as shown on the above photo.  The white targets with concentric circles and crosshairs (not visible in the picture) make it much easier to tell at a glance the degree of roll misalignment to within approximately +/- 1/64”.


The Microgage uses a class 3A laser, with less than a 5 milliwatt output, and is safe for the roll shop application.  It is widely used in similar industrial environments.  A class 3A warning label will be supplied.


An approximate price for one laser alignment system as described designed for a 50” Farrel grinder, complete with the Microgage 1000 standard system as specified in the catalog with power supply for 120 volt, laser mounting brackets, end cover, receiver mounting brackets for the headstock center and neckrest gibs, and journal targets is $15,000.00

The above price assumes two different roll setups on straight (not tapered) gibs - i.e.: two different diameter roll necks and end journals.  The final price could be higher or lower depending on how many roll setups are required.  This will be determined either by a site inspection, and/or by a detailed review of the drawings.  Once this is done, a firm fixed price quote can be supplied.

The price does not include field time and expenses by RGB Engineering to assist with the installation and setup.  This could be done by in-house people, but it is recommended that RGB Engineering be involved if possible.  RGB can also supply a field technician if shop mechanics are not available.  This work would be done at the normal service rates.

There is a one year warranty on the laser equipment provided by Pinpoint Laser Systems.

Delivery of the complete assembly is about 12 weeks; this could vary depending on the job complexity and workload at the time of the order. 

Terms: Net 30 days, subject to a 1-1/2% per month interest on overdue balance. Freight: pp & add, FOB Ansonia, CT.