I've made a couple Marv-style guided tap holders (easy to do, especially if you have hex stock handy), but still most of my tapping down to #2 size in non-ferrous metals is done "off-line" in a vise with a tapping block.
You can get fancy tapping blocks with a bunch of holes drilled in them of various tap sizes, or do what I do, which is every time I have a short (~1") nub of rod leftover in the lathe, face it off and drill it with whatever tap shank size I want a tapping block for (little taps all have the same size shank, which is handy). In use, oil the tap, stick the tap through the block, hold the block hard up against the bit-to-be-tapped (hopefully you've got a flat reference surface, otherwise, use a guided holder) and turn the tap, using either a T-wrench or the other sort, whatever they're called-- the two v-blocks screwed together. When done, I throw the tap block into the appropriate little drawer that size taps and dies live in.
For #4 and smaller taps, I've knurled and drilled some bits of ~1" rod and cross-drilled them for a set-screw and mount a tap in them. Easily turned by hand in soft materials with less chance of over-torquing. Put a reamed, sized hole in the 'rear' end and they double as guided tap holders too.
You can get fancy tapping blocks with a bunch of holes drilled in them of various tap sizes, or do what I do, which is every time I have a short (~1") nub of rod leftover in the lathe, face it off and drill it with whatever tap shank size I want a tapping block for (little taps all have the same size shank, which is handy). In use, oil the tap, stick the tap through the block, hold the block hard up against the bit-to-be-tapped (hopefully you've got a flat reference surface, otherwise, use a guided holder) and turn the tap, using either a T-wrench or the other sort, whatever they're called-- the two v-blocks screwed together. When done, I throw the tap block into the appropriate little drawer that size taps and dies live in.
For #4 and smaller taps, I've knurled and drilled some bits of ~1" rod and cross-drilled them for a set-screw and mount a tap in them. Easily turned by hand in soft materials with less chance of over-torquing. Put a reamed, sized hole in the 'rear' end and they double as guided tap holders too.