There are some much more expensive helical focuser that do have an extra fine additional control, but these are not common. Much like the geared crayford focusers.
I love helical focusers! The are low profile making them a great space saver. In ATM DIY visual scopes they mean you can have the focal plane of the scope closer to the tube allowing for the use of a smaller secondary mirror, meaning MORE LIGHT and better contrast. I'll be using a 2" helical focuser in a travel scope project I'm on.
PS, had to correct some things after re-reading OP.
Yes , I to love helical focusers . I have one on my 10 inch f/10 Newt ( in storage in NZ sadly ) and because they are such a low profile ( 30mm ) it allows me to have an only 'One inch ! ' secondary mirror , great planetary scope that one.
Its the 2 piece alliminium tube sections on the Dobbo mount in this photo .
Mine is an Antaries made one , very well made and super smooth..
Brian .
Yes , I to love helical focusers . I have one on my 10 inch f/10 Newt ( in storage in NZ sadly ) and because they are such a low profile ( 30mm ) it allows me to have an only 'One inch ! ' secondary mirror , great planetary scope that one. 
