Electric Motor Repair Electric Motor Maintenance-Martindale Products
phone:  216-521-8567
fax:       216-521-9476
Site Search:

Type C Commstone Holder
Printable Version of this page.

The Type C Commstone Holder is a compact grinder for slip rings and commutators up to 4-3/4" long.  This unit is especially valuable when the motor frame or brush rigging extends over the commutator or slip ring.
Best results are obtained when the armature is running at normal speed, in its own bearings, with centrifugal force holding the commutator in its true running position.
Use of a commstone frequently, for truing the face of a commutator, will help in avoiding the long and costly delay of disassembly that is required to turn an armature in a lathe.

• Only 3-5/8" long; fits in close quartered jobs.
Flexible in-feed defects to side in cramped quarters.
• Long and Short Handle may be used pivoted in any position.
• Choice of 2" Box or Stone Holder.  These are interchangeable and both may be ordered.
• Carriage travels is 1-1/4", on "Teflon" ways.
• Commstones for use with the 2" Box ( 1"
× 2" × 8"), or for use with the Stone Holder (1" × 1-1/2" × 6-1/2"), are available in all grades.
• Steel Carrying Case is available with space for commstones, small tools, etc.

Type C mounted on Auxiliary
Generator using only lower
part of adjustable support.


Base length: 3-5/8"
Base Width: (without wood handle) 4-3/4"
Height: (base to top of stone-holder nut) 3-3/4"
Adjustable Support: (part "B" from center of brush-arm hole to center of joint with part "A") 3-3/8"

Grinding Capacity

With 2" box and 1pc. 1" × 2" × 8" Commstone to 3-1/4"
With Stone Holder and 2 pcs. 1" × 1" × 6-1/2" Commstones to 3-3/4"
With Stone Holder and 2 pcs. 1" × 1-1/2" × 6-1/2" Commstones to 4-3/4"

Type C Commstone Holder: Catalog Number
Complete with Stone Holder long and short handles COMH100
Complete with 2" Box and long and short handles COMH101
Adjustable  Support (not included with
 Commstone Holder)
Stone Holder only COMH201
2" Box Only COMH202
Steel Carrying Case for Type C Holder CASE101
Net Weight, with Adj. Support: 4-1/4 lbs.
Commstones for above: Catalog Number
1" × 1" ×6-1/2" COMMXLS846*
1" × 1-1/2" ×6-1/2" COMMXLS847*
1" × 2" ×8" COMMXLS850*
*When ordering, specify catalog number and grade (i.e. EC, C, M, F, P)
(See Commstone descriptions under (Abrasives / Commstones))