Used Type 51 AR 21 – 83 1/2” HD Precision Knife & Surface Grinder

Machine Information

Main Machine Base:

  • Box/Cellular Construction – extremely Heavy throughout
  • Entire Base is Stress Relieved
  • Interior of Base is very open for easy access (lots of clearance) and cleaning (Bed Knives and Tub)
  • Easily Aligned and Leveled from outside along the length of the machine. (We will be happy to discuss our recommendations regarding the all important foundation requirements under the machine).

Machine Ways

  • The Reform Carriage Design allows Easy Access for Operation and Wheel Changing and Adjustment from the front of the machine (not the rear of the machine as on some competitive machines).
  • Accuracy along the length of the machine is better than .0005”/40” absolute
  • NEW: Machine Ways are Precision Machined prior to installation of Hardened Precision Ground Way Strips(Steel Bands) on the Tops of the ways as well as the rear side guiding ways.
  • The Carriage Rides on Hardened Precision Ground Steel Bands (Wear Strips) along the length of the base on the tops and sides of ways which can be easily and inexpensively replaced if need be after some years of use. This way if ever damaged or as they wear then they can be easily and inexpensively replaced in order to maintain the accuracy of the ways and machine. This is really important as there is always the possibility of damage and /or wear. The long term life of the accuracy of the machine is easily maintained and after many years of operation with proper cleaning & maintenance the machine ways can be easily restored to like new condition & accuracy
  • Adjustable Way Wipers also included. As a result of having the way wipers and the replaceable steel bands – Accordion Way covers are not required where they are required for machines equipped with hardened way in order to protect them as any wear or damage will affect the grinding accuracy of such a grinder.

Grinding Head Carriage

  • The Carriage is Wide with Maximum Distance between bearings in order to get maximum stability and accuracy while operating.. The carriage is Stress Relieved and is made of oversized, non-distorting, vibration-damping material
  • The Wide Carriage Design also provides Even Load Distribution and Maximum Rigidity.
  • The Grinding Head Carriage is carried on 4 Horizontal Re-adjustable with race roller bearings
  • 4 other bearings are used for Carriage Side Alignment. This system ensures a very accurate, easily adjustable carriage transmission system.
  • Grinding Motor Slides – Grinding head mounted on extra long hardened and ground flat guide and re-adjustable for wear with 3 adjustable wedges on either side.


  • Precision Grinding Motor – 12 HP – 1800 RPM (continuous duty rating), Dynamically Balanced & Manufactured by “Reform Motor Division”
  • Extra heavy duty, high precision Grinding Head Motor Spindle, mounted in precision taper roller bearings.
  • Any bearing play can be easily taken up with a special nut assembly on the bottom of the grinding head motor.
  • Motor is Totally Enclosed, sealed and windings are encapsulated in Epoxy.
  • Head is Slewable (Tiltable) for Concave & Surface Grinding.
  • Reversing Switch for main grinding motor included
  • Head is Cross-Adjustable for precision hollow positioning
  • 10” Diameter Grinding Wheel & Backing Plate with “Quick Change Keyhole Type Hub Assembly”. (Can use 10” Segmental Head on this machine if you want but not recommended for your job).

Downfeed & Control Of Grinding Head

  • The Vertical Feed of the Grinding Head is through the use of a Servo Motor which is directly coupled to a Vertical Oversized Ball Screw (with Double Nut Assembly), completely eliminating any play, which might develop over the life of the machine. The double nut automatically self adjusts nut to screw for any wear which might develop.
  • For highest grinding precision, the ball screw is axially pre-tightened with a combined thrust-radial bearing corresponding to the grinding motor and carriage weights, in order to ensure automatic weight balancing. The guide ways, spindle gear and ball screws are mounted under covers, additionally protected with wipers and the maximum up/down movement pre-tested with limit switches.
  • Power Up & Down to the grinding head with push-button control (greatly reduces setup time) as well as handwheel infinitely variable speed up & down
  • Automatic Electronic Down-feed System enables the operator to preset the machine with a Set Finish Point so that the grinder will proceed at a certain amount of down feed per stroke, back and forth.

Note:With this the grinder man can do other jobs with the machine automatically grinding and then with auto shutdown at the end of the preset program.

Grinding Programs

  • Grinding Cycle
  • Roughing
  • Finishing – Sparkout
  • And Auto Return to start position with machine shut down with completion of grind.
  • Automatic Down feed is Infinitely Variable .0002” to .008” per pass (0.005 to 0.2 mm/pass)

Longitudinal Carriage Feed System

  • Grinding Head Feed: 33 and 66 ft/min. (10 and 20 m/min) reciprocal grinding.  (Infinitely Variable Optional)
  • The Feed System utilizes a Rack and Pinion Drive System (Helical / Angle Cut)– for assured continued smooth operation (even as wear develops) giving very smooth drive characteristics and smooth carriage reversing and head direction.
  • With this system it is a very positive drive for heavy or light grinding and it does not wear and cause a jerking motion like some other drives will over a period of years of operation.
  • It is also very easily maintained (when worn) (ie. replaced – Rack is in approximately 40” long sections doweled into position)
  • The Helical Pinion is belt driven so if there is a reverse failure, the belt will slip rather than hurt the pinion. If there is a drive failure, the carriage will go to the end of the machine and there are rubber hydraulic shock absorbers to protect the carriage and base.
  • Grinding Length can be easily varied by movement of length stops – carriage is reversed by the use of non-contacting proximity switches.
  • Longitudinal Travel can be easily started or stopped by electrical means.

Coolant System

  • The Coolant is pumped by a powerful pump from the Separate Coolant Tank, which sits at the right end of the grinder. The coolant travels to the grinding head carriage and then the flow is split.  One Outlet Goes Through the Hollow Spindle of the Main Motor to the end of the shaft where it is defected out to the inner side of the grinding wheel (which is the hottest spot of any grinding – when the carriage is traveling to the right and is really where the coolant is needed for cool grinding and long wheel life).  The Other Outlet goes to a nozzle directed at the outer edge of the grinding head being used and material being ground.  Each nozzle has a Mechanical Valve for control of volume of flow to each nozzle.  This full flush cooling ensures a cool knife and a clean wheel for the best possible grind and super wheel life.
  • Cooling through the Spindle also ensures constant cool motor temperature hence longer life and tighter bearing set-up/loading (hence no bearing play).
  • The Coolant then proceeds with the swarf to the left hand end of the machine where it flows out into the separate tank along the back of the machine for final separation and cooling. (See Optional Coolant Cleaning Systems).
  • There is a Wash down Hose supplied hooked up to the Coolant Pump. It is used to wash down the knives and the bed when finished grinding.  Also can be used as a coolant tank emptying hose.  (Variable Volume)
  • Coolant Tank includes an economical “Helmut” coolant cleaner system