When the proper micro tool is chosen for moldmaking, there are many parameters with which to deal. The most important is knowing exactly what materials are being machined and their hardness or toughness qualities, or “machinability”. Guessing or coming close on this point will lead to much wasted time and tooling.

The next parameter to consider should be the efficiency of the spindle (e.g. size and construction for rigidity, effective temperature control and accuracy). These spindles will generally be run at very high rpms compared to regular CNC machining processes, depending on the hardness of material and results needed. Proper machinery may be discussed with the tooling manufacturer, and many are available to the moldmaker.
If coolants are being used with coolant-through tooling, then viscosity, filtration, lubricity, cleanliness of sump and psi will all become additional factors with small tooling. Criticality is increased greatly.

To deal with these parameters, it is suggested that the moldmaker consult with the providers of the lubricants and apparatus involved. Suggestions also may be made by the tooling company during the purchasing process.
Between the spindle and the tool you need to consider the toolholding capacity. Here it is recommended that drills are held and run—depending on diameter—to within .0002″ t.i.r. max. This will ensure better tool life, tolerances, hole shape, etc. As the tooling gets smaller, the tolerance becomes tighter.

For extremely small drills, the tolerances should be held as close to “0” as possible. Yes, we are striving for perfection. This is the insurance needed to effect a successful end result.
Accurate toolholding may be accomplished with ultra precision collets or with hydraulic holders or shrink fit holders. All provide very close tolerancing when chosen carefully and used properly. Setups should always be verified prior to use. This is done by the use of good tool pre-setters. These can also be discussed with the tooling provider when purchasing the tools.

Some solid carbide drills are available from stock in 0.4mm (.0016″) to 6mm .236″) diameter sizes, in increments of .05mm (.002″). A line of solids from .1mm (.004″) to 2mm (.078″) diameter in increments of .01mm (.0004″) then from 2mm (.078″) to 3mm (.118″), in increments of .05mm (.002″) are also available.
Coolant through carbide drills are available from .0.75mm (.0295″) diameters to 6.0mm (.236″) diameters with increments of .05mm (.002″). They are all available in 6, 10 and 15 x dia. depth capabilities from stock.