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UDC'h81.3.042
IS0
FO R STA N DA RD I Z AT1 ON
I N T ERN AT1 O N A L O RG A N IZATl O N
IS0 RECOMMENDATION
R 841
AXIS AND MOTION NOMENCLATURE
FOR NUMERICALLY CONTROLLED MACHINES
1st EDITION
October 1968
COPYRIGHT RESERVED
The copyright of IS0 Recommendations and IS0 Standards
belongs to IS0 Member Bodies. Reproduction of these
documents, in any country, may be authorized therefore only
by the national standards organization of that country, being
a member of ISO.
For each individual country the only valid standard is the national standard of that country.
Printed in Switzerland
Also issued in French and Russian. Copies to be obtained through the national standards organizations.
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BRIEF HISTORY
The IS0 Recommendation R 841, Axis and motion nomenclature for numerically controlled
machines, was drawn up by Technical Committee ISO/TC 97, Computers and information processing,
the Secretariat of which is held by the United States of America Standards Institute (USASI).
of a
Detailed work on this question by the Technical Committee led, in 1967, to the adoption
Draft IS0 Recommendation.
W
In August 1967, this Draft IS0 Recommendation (No. 1315) was circulated to all the IS0
Member Bodies for enquiry. It was approved, subject to a few modifications of an editorial nature,
by the following Member Bodies :
Australia Italy Sweden
Belgium Japan Switzerland
Czech os1 ovakia Korea, Rep. of Turkey
Denmark Netherlands U.A.R.
France New Zealand United Kingdom
Germany Poland U.S.A.
Iran Portugal
Israel
Spain
No Member Body opposed the approval of the Draft.
The Draft IS0 Recommendation was then submitted by correspondence to the IS0 Council,
which decided, in October 1968, to accept it as an IS0 RECOMMENDATION.
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ISO/R 841 -1968(€
IS0 Recommendation R 841 October 1968
AXIS AND MOTION NOMENCLATURE
FOR NUMERICALLY CONTROLLED MACHINES
1. SCOPE
1.1 This IS0 Recommendation for axis and motion nomenclature for numerically controlled
machines is intended to simplify programming and to facilitate the interchangeability of
recorded data.
1.2 This IS0 Recoriinieiida'iiuri applies to all nuiiierically controlled machines.
No1-I:. I:or the uhc 01 >iiriplicitq. the majority of the text of this IS0 Kcçommcndation IS written in
terni5 which uc' ait?licdbie tu incichitic-tools but it is nevertheless applicable to numerically controlled
rnachineb in general
1.3 The technical terms used in this IS0 Recommendation are based on the data processing
vocabulary ISO'K . . .*.
2. PRINCIPLES USED TO NAME MACHINE MOVEMENTS
BASED ON A STANDARD COORDINATE SYSTEM
2.1 This IS0 Kecoiii~iiendation names ;1 coordinate system and the machine movements so that a
prugrammer can describe the machining operations without having to know whether the tool
appioaches the workpiece or the workpiece approaches the tool. He will always assume that the
tool moves relative to the coordinate systeni of the stationary workpiece as defined in
clause 2.2.
2.2
The standard coordinate systeni js J right-handed rectangular Cartesian one, related to a work-
piece mounted in a machine and aligned with the principal linear slideways of that machine.
2.3 The positive direction of moverrient of a component of a niachine is that which causes an
increasing positive dimension on the workpiece.
2.4 When the machine is used for drilling or boring (using only its three principal linear move-
ments), niovenient in the negative Z direction will drill or bore into the workpiece.
When the machine cannot be so used for drilling or boring. special rules are provided to
2.5
minimize inconsistencies on multipurpose machines.
2.6 On the schematic drawings of the machines, an unprimed letter is used when a tool movement
is being dealt with. When a workpiece movement is being dealt with, a primed letter is used and
the positive direction of this movement is opposite to the corresponding unprimed letter
movement (see section 10).
*
Now bring drafted within Sub-Coininittee ISO/TC 97/SC 1, Yocabulary.
-3
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ISO/R 841-1968(€
3. THE Z AXIS OF MOïïON
3.1 The Z axis of motion is (except as described in clause 3.6) identified by reference to a spindle
which imparts cutting power.
3.1.1 In the case of machines such as milling, boring and tapping machines, this spindle rotates
the tool.
3.1.2 In the case of machines such as lathes, grinding machines and others which generate a surface
of revolution, this spindle rotates the work.
3.2 If there are several spindles, one should be selected as the principal spindle, preferably one
perpendicular to the work-holding surface.
3.3 If the principal spindle axis remains constantly parallel to one of the three axes of the standard
three-axis system, this axis is the Z axis.
3.4
If the principal spindle axis can be swivelled and if the extent of its motion allows it to lie in
only one position parallel to one of the axes of the standard three-axis system, this standard
axis is the Z axis.
3.5 If the extent of the swivelling motion is such that the principal spindle may lie parallel to two
or three axes of the standard three-axis system, the Z axis is the standard axis which is perpen-
dicular to the work-holding surface of the work-table of the machine, ignoring such ancillaries
as angles or packing pieces.
3.6 If there is no spindle, the Z axis is perpendicular to the work-holding surface.
3.7 Positive Z motion increases the clearance between the workpiece and the tool-holder.
4. THE X AXIS OF MOïïON
4.1 Where it is possible, the X axis of motion is horizontal and parallel to the work-holding surface.
It is the principal axis of motion in the positioning plane of the tool or workpiece.
4.2
On machines with non-rotating workpieces and non-rotating tools (e.g. shapers), the X axis is
parallel to, and positive in the principd direction of cutting.
4.3 On machines with rotating workpieces (lathes, grinding machines, etc.), X motion is radial and
parallel to the cross slide. Positive X motion occurs when a tool, mounted on the principal tool
post position of the cross slide, recedes from the axis of rotation of the workpiece.
4.4 On machines with rotating tools (milling machines, etc.) :
4.4.~ If the Z axis is horizontai, positive X motion is to the right when looking from the principal
tool spindle towards the workpiece.
4.4.2 If the Z axis is vertical, positive X motion is to the right for single column machines when
looking from the principal tool spindle to the column, and for gantry type machines when
looking from the principal spindle to the l
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