Technical Information · issue 40 of 1995
Saw chain: New 3/8" RM chain types
IssueTI 40/1995
Full text
Page 1 of 3
Technical Information
40.95
STIHL 3/8" Oilomatic Rapid-Micro =RM= chain
&RQWHQWV
1. New cutter geometry (similar to Rapid-Super),
Tie strap on RM2 chain (matched to modified cutter)
2. Drive link geometry (flank angle changed from 90° to 80°)
3. Old / new comparison of chain types
4. Chain maintenance
5. Service notes
1.=New cutter geometry
The geometry of the 3/8" cutters has been
thoroughly revised and brought into line with the
shape of the time-proven 3/8" Rapid-Super cutters.
All essential characteristics were changed, i.e.:
• the whole cutter is 0.5 mm higher
• top plate rake angle increased
• depth gauge is now offset
• humped tie strap on RM2 has been matched to
revised cutter height
689TI002 KN
689TI004 KN
3/8" RM cutter Geometry of RM2 tie strap
old ------- old -------
new ________ new _______
The increase in cutter height and the wider top plate rake angle result in noticeable improvements in cutting
characteristics. The offset depth gauge helps enhance straight-line control of the chain which produces a
smoother cut and helps minimize the vibrations that inevitably occur during cutting.
)Technical Information 40.95 - Page 2
The outstanding features are:
• Higher cutting performance
• Reduced feed effort
• Improved cutting convenience and comfort
• Better component dependability
2.=Drive link geometry
Drive link geometry was revised at the same time
as the modifications to the cutters. The flank angle
of the drive link was changed from 90° (40°+50°)
to 80° (40°+40°). 50°
This helps improve the reliability of the chains 40°
when cutting hardwood and operating at extremely 40°
low outside temperatures.
689TI003 KN
The part number remains unchanged.
Drive link
old fo
-------
new _______
3.=Old / new comparison of chain types
====Chain type======arive=link=g~uge=================Type No.========================Type No.
mm =====in=======================O l d===========================N e w
33 RM 1.3 (.050) 3857 3989
35 RM 1.5 (.058) 3858 3990
36 RM 1.6 (.063) 3859 3991
33 RM2 1.3 (.050) 3921 3992
36 RM2 1.6 (.063) 3919 3994
33 RMF 1.3 (.050) 3888 3993
4.=Chain maintenance=========================================5.=Service notes
The existing sharpening aids and tools can be 5.1=Cutters
used without any changes for sharpening the new The new versions of the cutters (3991) and drive
RM chains and replacing chain links. links can also be installed in original-type chains
and vice versa.
Note: =kew, simplified sharpening instructions
will be used for all STIHL Oilomatic saw chains in 5.2=Humped tie straps
future - see TI 41.95. The new version of the humped tie straps (3994)
can only be used together with new versions of the
cutters (3991) but can be incorporated in original-
type chains. A combination of the original tie strap
(3919) and original cutter (3859) can also be used
in the new version of the chains.
)Technical Information 40.95 - Page 3
6.=Summary
Item Part Name Original New Rem.
version version
1 Oilomatic chain 33 RM 3857 3989
including items 7 to 9
2 Oilomatic chain 35 RM 3858 3990
including items 7 to 9
3 Oilomatic chain 36 RM 3859 3991
including items 7 to 9
4 Oilomatic chain 33 RM2 3921 3992
including items 7 to 11
5 Oilomatic chain 36 RM2 3919 3994
including items 7 to 11
6 Oilomatic chain 33 RMF 3888 3993
including items 7 to 11
7 Right-hand cutter 3859 662 0400 3991 662 0400 1)
8 Left-hand cutter 3859 662 0600 3991 662 0600 1)
9 Drive link 3725 662 1000 3725 662 1000 2)
10 Right-hand hamped tie strap 3919 662 3900 3994 662 3900 1)
11 Left-hand hamped tie strap 3919 662 4000 3994 662 4000 1)
Other chain parts as before
Modification to be introduced: in progress
5HPDUNV
1) Original version of part will be supplied from factory only as long as existing stocks last
2) Only modified version of part is available from factory
Last Technical Information on saw chain: 39.92
Waiblingen, September 18, 1995 Andreas Stihl - D1/MTK
© 1995 Andreas Stihl Technical Documentation Page 2 of 3
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Extracted from the manufacturer's 2012 service catalogue. Most of these PDFs embed fonts with a shifted character map, so the text above was recovered rather than copied — read it as a faithful but imperfect transcription, and treat the page image above each block as the authority where the two disagree — the figures exist only there, because they are vector drawings that text extraction cannot keep.