Blank Carbide Micro Bits as Drill Bits

[jdrichard]

I have been having fun over the years drilling small holes for actions such as re-pivoting.  The sizes I typically work with is 0.25mm to 1mm.  I have been using PCB Board drills and they would usually break and remain in the hole.  So what I do now is snap them off closer to the base, then make a "screwdriver like" tip using a 2000 grit diamond plate.  This does work but the spiral part of the shaft does weaken the shaft.

So, what I would like is a blank .25mm Carbide shaft that I can Chuck Up on my lathe tailstock where I have prepared the end as a flat or roof like pivot drill (like the. old ones from 100 years ago).  Or one that looks like the PCB drills that is a shaft and not spiral.

Any thoughts or suggestions.

JD

[nickelsilver]

I like to use 1mm rod for making small drills. You can get it from Travers on that side of the pond.

 

https://www.travers.com/product/micro-100-srm-solid-carbide-metric-round-blanks-527624?size_3615[0]=1mm

 

I hold it in a pin vice with a square head, then grind to the classic pivot drill shape like is illustrated in the Levin book. First I grind it more or less like a screwdriver blade, then grind the lips, then narrow the sides until it is the right diameter. The square head pin vice become the "indexer"; doing it all freehand and eyeballing (and measuring for the diameter) you can make up a drill in just a few minutes. A diamond wheel really makes things go faster and you can get a better finish, I like a D7 (7 micron) for finishing small drills. Too coarse and the edge breaks down very fast in use, and for really small drills like 0.10mm anything much coarser just breaks it as you try to grind. A D15 is OK too.

 

AWCI has a video from Ron DeCorte showing how to hand grind the drills; in the video he uses carbide tipped dental burrs as blanks, but the process is the same.