[Groff] offset scaling with .bd

[Daniel Senderowicz]

The original troff reference manual mumbles something like:

 .bd F N  "The characters in font F will be artificially
              emboldened by printing each one twice, separated by N-1
              basic units. A reasonable value for N is 3 when the charater
              size is in the vicinity of 10 points..."

However, unless I use values for N of the order of a few hundreds
(e.g.  600) the emboldening is negligible.  The gnu groff manual
mentions something about .bd that I don't understand if has any
relevance to this problem. Perhaps someone can educate me on how
the scaling of the offset in the .bd command works.

Thanks.

Dan