How to offset a part of a spline

[JoeS09]

Hello, can anyone please tell me the individual steps involved in offsetting that half of a spline to the left of the line shown in the attached drawing done in AutoCAD 2018?

Spline offset.dwg Spline offset.dxf

[SLW210]

Not sure why you are having trouble, pretty straight forward. The OFFSET SPLINE looks very little like the original. Break either side and extend (or BREAK @point?), then OFFSET>20

 

Command: BR
BREAK
Select object:
Specify second break point or [First point]:
Command: EX
EXTEND
Current settings: Projection=UCS, Edge=None, Mode=Quick
Select object to extend or shift-select to trim or
 [Boundary edges/Crossing/mOde/Project]:

Select object to extend or shift-select to trim or
 [Boundary edges/Crossing/mOde/Project/Undo]: *Cancel*

Command: O
OFFSET
Current settings: Erase source=No  Layer=Source  OFFSETGAPTYPE=0
Specify offset distance or [Through/Erase/Layer] <Through>: 20

 

[Dadgad]

Are you expecting the offset Spline to be identical to the original?

It won't be. 

[JoeS09]

Hi again, many thanks for these replied, very helpful.

firstly, I  am a newby, and have never came across the BREAK command before

secondly, the spline was a quick and irty one drawn for this thread. The odds are 1,000,000 to one that the two halves were almost identical