Operating Instructions: 51 & 51-L Barnhart Grinders

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No. 51-L Barnhart Band Wheel Grinder with 60" bed.  No. 51 Barnhart Grinder has a 40" bed.  The 4-screw end brackets shown are standard on both models, replacing older type 8-screw end brackets.

For mills with limited space for mounting the Barnhart Grinder, a motorized head is available as an accessory to fit both the Nos. 51 and 51-L models in place of the standard friction head.  The motorized head both drives and grinds the band wheel.  A toothless saw or belt is not needed to drive the top band mill wheel, providing a much simpler and easier set-up.  The bottom wheel is usually ground with the standard friction head shown above, rather than disconnecting the power on the mill.

Alignment and setting of grinder:
  • To align the bed of the grinder with the axis of the band wheel, scribe a line square across the face of the band wheel as shown at "X" and "X" in fig. 1.
  • With a steel scale or similar tool used as shown in fig. 2, check at each edge of the band wheel.
  • If the bed is not square across face of band wheel, the face of the band wheel will be ground HOLLOW.
  • To obtain the approximate parallel of grinder bed with axis of band wheel, use the steel scale in the position shown and measure from a selected point on the upper surface of the carriage out to the face of the band wheel at or near each edge.
  • We suggest that for final parallel setting a reasonably wide surface of the band wheel be ground and then check circumference at each edge of the ground surface with a steel TAPE.

 

Location of Grinder in Relation to Rim of and Center of Band Wheel:
  • With the stem of the SETTING TOOL resting in the shallow groove in the upper surface of the CARRIAGE and against one of the shoulders, and the 2 points at "Y" and "Y" contacting the face of the band wheel, the grinding wheel and the grinding head will be in the correct relative alignment with the center of the band wheel.   And with the scribed line on the side of the stem of the setting tool at "Z" registering with the scribed line on the upper surface of the carriage, the bed will be the correct distance from the face of the band wheel.
  • Where possible, have this distance from face of band wheel as shown.

 

 

 

 

 

 

 

 

 

Speed of Band Wheels:

The No. 51 Band Wheel Grinder is equipped with ball bearings in arbor, and is suitable for grinding with band wheels running at full speed.

 

Driving Upper Band Wheel:

Use an old band saw with teeth cut off for driving the upper band wheel for the grinding operation.  Cutting off the teeth is an important safety measure.  Where convenient use a standard length saw, and have the alignment of the band wheels in their sawing position.
IMPORTANT:  Be sure to secure planks around the saw to insure protection to the operators.  Also, cover all the spaces where tools may by accident fall in and go around the lower band wheel and go between the saw and the band wheel.

 

Depth of Cut and Feed:
  • Barnhart Band Wheel Grinders will grind exceptionally fast, but like all grinding machines there are limits to the abuse they will stand up under.  Remember this is a grinding machine, and accurate work is the objective.
  • When grinding cast iron band wheels, do not attempt cuts deeper than .001" to .002" (.025 to .050 mm).  Feed about 4 to 8 turns of the feed screw per minute.
  • Don't set for depth of cut after each cut across the face of the band wheel.  Make a return pass across and note the cut the grinding wheel is taking.  If it is taking a cut of any appreciable depth, the feed in relation to the depth of cut has been a bit too fast.  Accuracy being the principal objective, refrain from rushing the job.   It is good and safe practice to take lighter cuts with a faster feed than to take deep cuts with a slow feed.
  • Keep the cross feed mechanism locked tight with tall nuts when grinding.
  • For finish cut, feed repeatedly across face of band wheel and keep grinding wheel turning until the grinding wheel virtually quits cutting.

 

Making Grinder Right or Left Hand:
  • The long feed screw may be inserted at either end of the bed.
  • Use kerosene on dovetail slides and feed screw.  Heavy oil clogs with dust.

 

Changing Grinding Wheels:
  • To remove wheel assembly when replacing worn wheels release two screws, one on each side of fork, unscrewing these until they come free of the bearing.  Wheel assembly can then be lifted out of fork.
  • Before putting on a new grinding wheel, thoroughly remove the dust from the parts around the grinding wheel.  Take all necessary precautions to prevent dust from getting near the bearings.
  • After changing wheels, screw adjustment should be taken up just enough to remove end play, but so that the wheel spins freely.

 

Type of Grinding Wheels:

Use 6" x 2" x 2" (150 x 50 x 50 mm) resinoid straight face grinding wheels No. 37C24-04B5, or equivalent, made to stand grinding with band wheels rotating at full speed.  It is important to use only the above type abrasive wheels, which are usually available from abrasive wheel suppliers.  They are recommended for grinding either cast iron or steel band wheels at any speed.

 

Grinding Band Wheels Flat or With Crown Face:
  • Band wheels ground with a flat face at full speed of band wheels will show a slight crown when the band wheels are stopped and measured.  This effect is produced by the action of centrifugal force.
  • Should a crown face be desired, the following method of grinding is suggested:
  • First, the wheel should be ground flat, and even thought the centrifugal force will show a slight crown, the two outside edges of the band wheel should tape exactly the same.   When more crown is desired, the normal crown used is approximately .001" (.025 mm) for each foot (300 mm) in diameter of the band wheel.  Generally the high point of the crown is back 1/3 from the front edge of the band wheel on a single-cut saw.   The high point is on center on a double-cut saw. 
  • To grind the crown, while the wheel is running mark the location of the high point with a piece of chalk.  Make the mark about 1" (25 mm) wide so it can be easily seen.   Then grind more material away on each side of the chalk line to produce the crown without adjusting the set-up for the Barnhart Grinder.  This may be done by moving the Barnhart Grinder head to the outer edge of the band mill wheel.  Then feed in, taking a heavier cut, and traverse towards the center.  Since the grinding wheel is being dressed away during the grinding action, it develops a crown due to the wear on the grinding wheel.  This same operation is repeated on the opposite edge of the band wheel.
  • By placing a straight edge across the face of the wheel, and using a feeler gauge, or paper, to check the crown at the two edges, you will find that with a piece of paper on the outside edge of the band wheel that the straight edge will touch the two pieces of paper and the high point where it was chalked.

 

Taping Wheels With Saw On:

Checking the circumference of the band wheel when the saw is on can be done without removing the strain on the saw.   Before attempting this procedure, solder the ring on the end of the steel tape.   If this is not done the pressure will break the ring fastening.

 

Bearings:

This grinder has two SKF No. 6203-2Z ball bearings in the head.  These standard automotive bearings come lubricated from factory to last entire life of bearing without further lubrication.  Replacement bearings can be obtained from almost any mill supply house or automotive supply house.   Either SKF or other interchangeable makes.

 

Suggestion:

We suggest that you provide a box in which to keep these instructions, the grinder head and all small parts.  Keep box covered.

 

Note:

In some instances the assemblies shown may differ from those on your machine.  These changes represent improvements made for more efficient operation.  Not all improvements are interchangeable.  If the assembly shown is different from that on your machine, please give description of the parts you are using.


Copyright(c) 1998-02, Armstrong Mfg. Co., All Rights Reserved
2700 SE Tacoma St., Portland OR  97202
voice: 800-426-6226  fax: 503-228-8384
e-mail: info@armstrongblue.com

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