Hacker News Reader

Comment by transfire | Hacker News Reader

What is the smallest drill bit one can buy?

PCB manufacturers specify their minimum via sizes. Probably that is the smallest usable drill bit size made in quantities. JLCPCB says minimum 0.2mm so there's what you got.

Keep in mind you will need a air bearing spindle that runs at high x10k RPMs to actually use them.

For smaller holes we zap them in the material with lasers.

They go even smaller than 0.1mm. McMaster-Carr sells a 0.051mm drill bit for $25: https://www.mcmaster.com/8904A11/

That's the absolutely small I could find, though I suspect specialty vendors have even smaller ones. You can find MMC's other micro drill bits here: https://www.mcmaster.com/micro-drill-bits/

My only experience with these was in school where we used 0.25mm micro end mills (like a drill bit that cut sideways) to cut our own PCBs. A small desktop micro CNC would just cut the traces out of a blank copper clad board. That's when I learned how easily these bits can break, so even though they're not that expensive you go through them very quickly.

>0.051mm

Holy shucks... How are they even manufactured? I imagine they have really precise grinding tools to make the flutes..

Sphinx uses laser ablation for their smallest drills (0.0030mm is their smallest catalog item, but they've made smaller as special order parts).

They can be pretty small. I purchased this set sometime back. It’s served me well. Gyros® HSS Wire Gauge Mini Twist Drill Bit Set |Includes 20 Micro High Speed Steel Bit Sizes #61 to #80 | with Convenient Clear Dome Storage Case (45-22010) https://www.amazon.com/gp/product/B000SKVF8I.

I frequently use a bigger size for fabricating reinforced epoxy with paper clips serving as rebar. Gyros Micro Drill Bit Set of 25#57 Drill Bits–Small Drill Bits for Jewelry, Plastic and Soft Metal–Mini Twist Drill Bit Set for Pin Vise Hand Drill, Rotary Tool - Carbon Steel Wire Gauge Drill Bits

Out of curiosity what do you use the paperclip reinforced epoxy for? Some sort of mold making?

usually it's for repairs of broken things, plastic tabs, random cast models, appliance parts, stuff like that. I'll drill a routing for the paperclip to thread through, then I bend and thread the paperclip through the tunnels, then I backfill the epoxy over the voids. They've usually been pretty tough durable repairs that hold up pretty well.

A #80 tap drill is 3.4x bigger (.343mm) than the one they're showing in the video (.1mm). Which isn't to say they aren't impressive, but they're typically made of HSS, not solid carbide.

.1mm is about 4 thou (.004"), or the thickness of a piece of paper. I'm being a little loose with the numbers here, but they're in the ballpark.

Sphinx Tools lists 0.03mm (30µm) drills in their standard catalog[1]. IIRC they made the 10µm drill Kern used to demo drilling holes in a hair to show off their pyramid nano CNC.

[1] https://sphinx-tools.ch/en/catalog-products-eshop/drilling-a...

A local hobby shop sold a kit with ten bits, 1.0mm down to 0.1mm, which I bought on a lark several years ago.

The middle sized bits are occasionally useful to (carefully!) finger-drill a tiny hole through a plastic part. They're rigid, very sharp, but pretty breakable if you're not careful.

The 0.1mm bit is so small that it's upsetting even to look at. I've never taken it out of the case.

0.1mm: https://www.aliexpress.us/item/3256801655537532.html

I would not expect you to be able to use bits this small without special machinery.

I've used similar 0.8mm drill bits by hand, and they were fragile enough.

Reply on news.ycombinator.com