Electric Motor Repair Electric Motor Maintenance-Martindale Products
phone:  216-521-8567
fax:       216-521-9476
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Martindale Commutator Grinding and Turning Tools
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Available in 2 styles in lengths from 6" to 48".  Will grind, with commstones, 1" beyond base at each end or turn, with turning tool, 2" less than base length at each end.

At right: Turning Tool Head
 Fig. 5

Used where there are no obstructions
to interfere with crossfeed handle.

The Martindale Commutator Grinder assures concentricity of the commutator or slip-ring by precision grinding while it is turning in its own bearings at operating speeds and temperatures, with centrifugal force holding each bar in place.
Either tool (Fig. 1 or 8) can be quickly changed from right to left hand operation.  On Fig.1, remove two screws and turn the cross-slide around.
On Fig. 8, the right-angle driving shaft is removed and inserted in the other side if the right-angle housing, and the grinding Head cross-slide turned around as with Fig. 1.
When grinding use 2" × 2" × 8" Commstones in any of the 5 grades shown and described under Abrasives: Commstones, Brush Seaters, Sanding Bands, etc.; Commstones (General Information) and Commstones (Commutator Resurfacing Stones).  The stones will grind 1" beyond the grinder base at each end. and they can be cocked to get into the corner at the riser.
If very deep grooves must be removed, the Fig. 5 Turning Tool Head may be used.  It is interchangeable with the Grinding Head on either Fig.1 or Fig. 8.  The tool holder should be positioned as indicated in the upper left corner of this page.  The top of the commutator should rotate away from the operator so that if the mounting should slip, the tool bit would be pushed away from the commutator instead of digging in.  It is necessary to add 4" to the grinder base length when using the Turning Tool.

Power-Drive For Either
Style Grinder
Reduces tedious labor; speed up the job.

Power-Drive eliminates the need for the operator to hank crank the head back and forth across the face of the commutator.

Weights: Figs. 1 or 8 with 12" base, Net 29 lbs., Shipping 38 lbs; add about 2 lbs. for each additional inch.  Power Drive unit, Net 27 lbs., Shipping 32lbs.

Used where end frame, fan, etc., would
interfere with crossfeed handle of Fig.1.

Grinders: (Carrying Case
included with grinders below)
Catalog Number
Commutator Grinding Tool (Fig. 1), w/ 10" base or less GRDR300*
Commutator Turning Tool (Fig.1), w/ 10" base or less, with Fig. 5 Head instead of Grinding Head GRDR301*
Right-Angle Grinding Tool (Fig. 8),
 w/ 10" base or less
Right-Angle-Turning Tool (Fig. 8),
w/10" base or less, with Fig. 5 Head instead of Grinding Head
For Grinders 10" to 26": add per
inch over 10"
(Grinder prices 28" and over on application.)
*Add base length to P/N when ordering
(i.e.:"10",12", etc.)
Power-Drive and Accessories,
 115V., 60 Hz
230 V.,50 Hz. GRDR501B
Turning Tool Head (Fig. 5), including Tool Holder GRDR505
Fig. 2 "L" Support GRDR50202
Fig. 6 Wedge Block GRDR50206
Fig. 9 "T" Support GRDR50209
Extension Handles (Fig. 7):  
6" GRDR50306
10" GRDR50310
Commstones for above:  
2" × 2" × 8" Plain Lathe Type


*When ordering, specify catalog number
and grade
(i.e. EC, C, M, F, P)
(See Commstone descriptions under
(Abrasives / Commstones))

Fig. 7 Extension Handle

The Round Stud Supports are both drilled 1-1/4", and fibre bushings are provided for bushing the hole in the support to the diameter of the brush stud.  The bushings also serve to insulate the Grinder when used on live brush studs.
Adjustable Wedge Blocks usually can be mounted on the brush arms in the same holes by the same stud bolts that fasten the brush holders, as shown in the illustration.
This extension can be supplied in a 6" or 10" length to extend hand-wheel past brush rigging or other obstruction, when necessary.

  Grinders 16" or less require 2 supports
  Grinders 18" to 34" require 3 supports
  Grinders 36" and over require 4 supports

  Grinder bases have mounting holes (3/8" - 16 thread)
  on 2-1/4" centers across the base and on 2" centers
  along the base for mounting supports.

A variable speed gear-motor controlled by a full-wave SCR control is attached to either Fig. 1 or Fig. 8 grinder by a positive drive coupling. A reversing switch, mounted on the carriage, is operated by adjustable stops mounted directly to the bed casting providing positive drive to the carriage.