It is possible with some effort. I can outline the details but might need some tweaking.
1. Create a new drawing (without using your default drawing).
2. Load your custom linetype one at a time using the Linetype manager. NOTE: Do not use multiselect to load all linetypes together. Keep track of these linetypes names on a paper in the order you are loading as you will need these names later. Close the linetype manager by clicking OK.
3. Draw one line of each of the linetypes loaded.
4. Click on File-Export-DWG-ON Layers. In the file dialog make sure "Translate user-defined line types to continuous line definition" is turned OFF and enter dcadlines.shx as the filename (at c:\ for example). Make sure c:\dcadlines.shx exist on the disk before proceeding further.
5. If you already have shx2shp.exe skip to step6 or download shx2shp.exe ( available inside zip file) from
ftp://ftp.sac.sk/pub/sac/utilprog/shx2shp.zip (this is gui version) or search google for more options.
6. Decompile dcadlines.shx to dcadlines.shp using the above gui version. Your older DOS version will need command line parameters to decompile the shx to shp.
7. Open this file using notepad only.
11. This file will look something like this
Code: Select all*5,25
2,8,(2,0),1,8,(0,-100),1,8,(66,0),1,8,(0,100),1,8,(-66,0),2,8,(2,0),0
*6,25
1,8,(0,50),1,8,(35,0),1,8,(0,-100),1,8,(-35,0),1,8,(0,50),2,8,(100,0),0
*7,37
....
12. Each shape starts with star '*' character. There is no name associated with these shapes. Now append the names one by one (in the order you added your linetypes) so that the above file looks like
Code: Select all*5,25,LINE1
2,8,(2,0),1,8,(0,-100),1,8,(66,0),1,8,(0,100),1,8,(-66,0),2,8,(2,0),0
*6,25,LINE2
1,8,(0,50),1,8,(35,0),1,8,(0,-100),1,8,(-35,0),1,8,(0,50),2,8,(100,0),0
*7,37,LINE3
13. Save and close this file. Copy this file to ACAD's Support folder.
14. Using Notepad only Open Acad.lin or create a new dcad.lin file from ACAD's support folder.
15. Repeat for each linetype you want in ACAD, add the following lines by replacing LINE1 or Line2 with your linetype name at both places. This linetype should be present the dcadlines.shp file.
Code: Select all*LINE1
A,0.0001,[LINE1,dcadlines.shx,s=.001],-0.25
*LINE2
A,0.0001,[LINE2,dcadlines.shx,s=.001],-0.25
and so on
16. Save and close this file.
17. Launch ACAD and create a blank drawing. At the command prompt enter "compile". Select dcadlines.shp from Support folder. A new file dcadlines.shx will be generated.
18. You are now ready to use your DataCAD linetypes. Simply open Linetype manager and load from either acad.lin or dcad.lin (as in step14).