I need to use a 1/16 router bit to cut through a 1/2" piece of MDF. Is there a bit with a long enough shank that will allow me to do that or what are my options? I am curing small letters with a cnc machine and the 1/8" bit is too large and distorts the letters.
Good luck not snapping the bit, which is the practical reason such bits are hard to find.
1/4" cutting length might allow (with proper registration) cutting from both sides (have to mirror the cutting file when flipped, of course.)
Looking (as I usually do, since supply is much better) for end mills, 1/16" end mill extra long brings up several options, including 1/2, 5/8. 3/4 and 0.95 inch cutting lengths.
1/16" router bit extra long does get some useful hits as well, including some with 1 or even 1.5 inch cutting length, but those (at least the ones I looked at) are pointy cones, not straight bits - if your software understands the shape, you'll break fewer bits, but still be able to detail the surface.
As far as I recall we are still not a shopping site, so I'll provide keywords but not links to products.
In either case, wear your safety glasses and expect to break some bits, or change the design/process to cut with a larger bit, or a laser, or something better suited - long skinny router bits (and endmills) do break in real life.
Making the small letters out of thinner material would be an obvious alteration towards success.