? endmills and weldon flat endmill holders, various shapes and sizes.
? stub length drill bits
? hold down sets for mill
? dovetail cutters
? t-slot cutters
? horizontal/vertical rotary table
? tilting angle base compatable with rotary table, if it isn't built in.
? collets
? tailstock to go with rotary table
? milling vice - consider kurt as the chinese ones can leave a lot to be desired.
? swivel base for vice
? toolmakers insert vice
? clamp down sets
? boring head for mill and boring bar
? parallels for holding work up in the vice
? slitting saw arbor and blades
? fly cutter
? fishtail threading gage (for aligning tool to work) and an ACME screw thread gauge.
? metal, plastic to cut (online metals has some assortments but you will need some bigger stuff as well)
? reamers
? angle blocks for setting up work at an angle in vise, measuring, etc.
? spiral point (best for through holes) and/or spiral flute (blind holes or through holes) taps, tap wrench
? countersink bits
? transfer punches
? cam clamps or toe clamps
? machinists? parallel jaw clamps, c-clamps
? machinist squares
? right angle blocks
? 123 blocks, 246 blocks
? Machinists? jacks
? edge finder and/or wiggler
? gear cutters or free running hobs, or a fly cutter style
? deburring tool
? DRO (expensive, optional)
? radius turning attachment (optional)
? better drill chuck for mini-mill
? expanding mandrels or arbors
? vice work stop
? steel letter/number stamps sets
? v-blocks
? ring light for mill
? x-way cover for mill
? way lube/spindle lube
? tachometer
? horizontal bandsaw for cutting stock, bimetal blades. In a pinch, you can cut them on the mill
Some sources: Shars, Travers Tool, Enco, MSC, Grizzly Ind., Tools4cheap, CDCO, Little Machine Shop, Ebay, Machine Shop Discount Club, Reid Tool Supply, Anytimetools.
Please feel free to add to this list!
Best,
Nelson