Diamond D Commstones
QUICKLY REMOVE FLAT SPOTS, HIGH BARS, GROOVES, RIDGES,
HIGH MICA, AND OTHER COMMUTATOR AND SLIP RING DEFECTS
Regular Maintenance of commutators
and slip rings with Martindale Commstones is so easy it enables you to
eliminate the above defects in their early stages.
With Commstones, it is not necessary to take a machine out of service to
resurface its commutator, thus production time is saved and
time-consuming major overhauls can be prevented.
ADVANTAGES OF GRINDING OVER TURNING
Turning a commutator is an expensive operation and, furthermore,
necessitates taking the machine out of service. For these reasons
it is customary to postpone the turning until the machine gives serious
On the other hand, if Martindale Commstones are applies as soon as the
defects appears, it will be eliminated before it has a chance to become
A flat spot 1/16" deep will not be cleaned up until 1/16" of copper has
been ground away from all other parts of the commutator. When the
commutator is clean and bright all the way around, the grinding is
finished and no more copper has been removed than was absolutely
The use of hand stones on any commutator even with large flats (if the
stone is twice as long as the width of the flat spot) will not leave the
commutator eccentric unless it is already so.
COMMSTONES WILL DO
1. Cut copper faster than a turning tool.
2. Cut copper, brass or steel without clogging.
3. Cut the edges of every bar clean - no dragging of copper.
4. May be used on either flush mica or undercut
5. Remove ridges, flats, high bars, high mica, quicker and more
effectively than any other method.
6. Save from 75% to 95% of the cost of turning a commutator.
7. Save from 80% to 99% of the time required to remove an armature and
turn the commutator in a lathe.
8. Grind under full speed operating conditions where every bar is held
in its true operating position by centrifugal force and leave every bar
perfectly rounded even when some of the bars are loose.
9. Remove less copper than the most careful workman would with a turning
10. Commstones are perfect insulators and may be used while the motor
or generator is operating under normal voltage and even under full
load. They can be used with perfect safety on any commutator on
which sandpaper can be used.
Sandpaper only cleans a flat
spot - Commstones Remove it!
DIRECTIONS FOR USING
If grease or oil is present, wipe or
sandpaper the commutator thoroughly before applying the stone.
Run the machine at full speed.
Do not rock the stone; hold it firmly in order to get a true arc as
quickly as possible.
Apply with sufficient pressure to get rapid cutting. If the stone
wears faster on one side than on the other, it is because pressure was not
applied perpendicularly. This may be corrected by turning the
stone three or four times until the full face has been obtained.
During grinding, move the stone slowly from side to side. This
will prevent ridges in the commutator from wearing grooves in the stone.
Large stones which are difficult to move while grinding may be held in
one place for a few seconds, then lifted, moved about 1/4 inch, applied
again for a few seconds, moved again, and so on until the commutator
DON'T USE TOO
SMALL OF A STONE
MARTINDALE COMMSTONES can be
made in ANY SIZE.
A Commutator stone should be as long as will work freely between
adjacent brush sets, and should also be twice as long as the width of
the largest flat spot. This latter requirement may occasionally
make it necessary to remove one brush-holder stud during the grinding,
to prevent commutator ridges from wearing grooves in the stones.
A Commstone that meets these size requirements will give much better
results than too small a stone and will prove more economical.
If in doubt about the size to order, give us dimensions "W", "L" and "D"
of your commutator and we will supply the proper size.
Position the Commstone so that the top surface of the commutator moves
away from stone. As shown above.
NINE GRADES FOR
COMMUTATORS AND SLIP RINGS
For Commutators and Brass or
Copper Slip Rings:
GRADE EC (Extra Coarse) ─ 36 Grit) for
use where a great deal
of copper is to be removed and a fast cutting stone is desired for
pitted and grooved conditions.
GRADE C (Coarse ─ 46 Grit) recommended for general cutting.
GRADE M (Medium ─ 90 Grit) for use where only high mica or
a small amount of
copper is to be removed.
GRADE F (Fine ─ 120 Grit) recommended for general
finishing, for periodic preventative maintenance or removing small
GRADE P (Extra Fine or Polish ─ 220 Grit) for finishing or polishing
/ burnishing where a high mirror-like polish is desired.
GRADE EP (Extra Polish ─ 320 Grit) for finishing of small
For Cast Iron and Steel Slip
Rings: ─ When using on cast iron or steel slip rings, run at
1800 or more surface feet per minute.
GRADE SRC (Coarse ─ 36S Grit) for removing large quantities of
GRADE SRM (Medium ─ 60S Grit) for general use and removing pits.
GRADE SRF (Finish ─ 90S Grit) for finishing.