Sharp AE-X9JJ Manual do Utilizador descarregar pdf (Página 14)

COMMUTATOR UNDERCUTTING

After the commutator has been satisfactorily resurfaced, the mica insulation separating the copper segments must

be undercut. Undercutting is one operation that is most easily accomplished with the armature removed from the

machine. Various tools are available, however, that enable undercutting to be performed on a commutator “in place”

without undue hardship.

Of the various undercutting practices used, only the two most common methods will be discussed herein.

There are three basic types of slots that can be produced by the use of circular cutters. The U-slot, the V-slot and

the Compound-angle slot.

MARTINDALE

• 1375 Hird Ave • Cleveland, OH 44107

Phone (216) 521-8567 • Fax Local 521-9476 / USA & Canada (800) 344-9191

E-Mail: [email protected]

Web Site: www.martindaleco.com

02/05

Helpful Hints For Saw Users

(Mica Undercutting Saws & V-Cutters)

Helpful Hints For Saw Users (H.S.S. Metal-Working Saws)

(Continued)

TEETH — Deep cuts and soft material require fewer teeth (for chip clearance) and stronger teeth (landed). — Thin material requires more teeth (at

least 2 teeth engaged in cut). — Hard materials and narrow slots (under .025”) likewise require more teeth. — Alternately

beveled teeth keep chips from sticking in the cut and in the tooth gullets. — Rake Angles: On center for iron and steel, 5° nega-

tive for yel low brass, from 5° to 10° positive for other soft materials.

BREAKAGE — In addition to causes noted under “MOUNTING OF SAWS”: Teeth break when starting a cut at too fast a feed, spindle bearings worn,

drive belts loose or sheaves worn, indexing before saw has cleared the slot, work-piece not tight, or the saw is dull (even the best

eventually wear out).

KEYWAYS — No keyways are furnished on saws under .020”. Thin saws will warp in the heat treating and grinding processes. Locked up between

good supporting washers, they will run true.

HUBS — will allow maximum side clearance when attempting to cut wood or plastics. They are helpful when spacing saws on an arbor.

RESHARPENING — In addition to grinding the tips of the teeth, all marks must be removed from the sides of the teeth. This can be done by grind-

ing the diameter below the marks or, as we do, by grinding the tips and clean-up grinding the sides. Either way the thickness is

reduced because of the hollow grind that is necessary for even the shallowest of cuts.

VIBRATION AND CHATTER — Arbor bent or worn undersize. — Work-piece improperly supported, particularly watch on thin material. — Teeth

too coarse/fine. — Speed too slow. — Climb milling, “Up-milling” is preferred, but climb milling may help on small parts to keep

them from being ripped from the clamping fixture. It may also reduce the bur. — Dull tool / Wrong clearance angles. — Feed

too slow.

EXCESSIVE WEAR — Seizing: Not enough coolant in the right place. — Not enough side clearance. — Cutter speed too fast and feed too slow.

The work may glaze and the saw will rub.

TOLERANCES — are expensive, don’t over-specify.

STEELS — M-2 is the best if the set-up is proper. We do have available saws from M-42 along with various surface treatments such as Titanium

Nitride.

SUGGESTION — If a saw is working well, send it to us and we will duplicate it. — If a saw is not working well, send us a used blade. We can some

times make recommendations from the marks on the saw.

Continued Next Page

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