I'm looking for artists who are well known for non hentai work, who also do hentai ?
? thanks

HIRANO Kouta, the author of Hellsing comes to mind, a few of his titles have that genre

Maybe Yamamoto Naoki and Harumi Chihiro? I'm not sure how mainstream they are.

Well... Most mangakas do hentai at some time of their careers. And It's interesting when you look for something of the same author and find these "other" works.

But most of them stop when they hit a mainstream series. And I think in most cases they are recruited to draw the story of another author.

So I'm gonna answer with the ones I think currently do both things (as far I remember by looking at the things I have on my lists):

Drawings - Series
IIDA Pochi. - Ane Naru Mono (Special case as the author makes the H version officialy)
SHOUNO Kotaro - World's End Harem
SAVAN - World's End Harem - Fantasia
774 house - Please don't bully me, Nagatoro
Butcha U - Sekkaku Cheat wo Moratte Isekai ni Teni shita n dakara, Suki na you ni Ikitemitai
TAKEDA Hiromitsu - Maken-Ki!
Fukudahda - Iinazuke Kyoutei
Tsuyatsuya - Rakujitsu no Pathos