Drilling small holes in hardend steel

Hi.

Trying to drill into old clock steel from the 18th century has not proved easy. Even cobalt failed.

I was trying to drill a 1.5 or 2mm hole but only got into the metal about 1/16th of an inch...any ideas?

Chris

One way would be to use EDM Chris....

Regards,

IanT

I saw this 'simple' EDM machine at GMES in 2016 - an electromagnet pulls the electrode up when the tip discharges through the work - sorry cannot find the details at the moment - but the gentleman who built it was very helpful and explained it for me. It would also be good for removing broken taps, making holes in HSS etc...

Perhaps someone else will know more detail of the design...

( Is there a way to rotate photos? )

Regards,

IanT

Try a good brand name solid carbide drill bit at high speed. The straight fluted type.

Edited By Hopper on 16/02/2020 23:22:15

Anneal it?

A drill with Cobalt in it won't be much different to an HSS one, could try a Carbide one but would need a solid setup.

Annealing and re hardening sounds the better option.

So how did they do it back in the 18th century?

For that type of work I usually favour a centre cutting carbide slot drill on the mill at highish speed. Works well on things like Aldi digital calipers when adapting to a simple readout for the lathe tailstock. Disadvantage of using carbide is if a big chunk breaks off in the hole and gets stuck. Another option is have you got a local firm for wire cut EDM ? These companies mostly have a start hole machine that can burn through hardened steel very quickly, a 1mm hole through 50mm of steel in less than 10 minutes is achievable but positionable accuracy is not that good.

In toolmaking the dies for punching are wire eroded to size an a hole is spark eroded through to allow the cut wire to be threaded. They can cut through up to 6 inch of hardened steel where I worked. You should look for someone with that capacity to spark through it dosn't take long. Look for die and toolmaker.

David

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Chris hasn’t actually disclosed what he is trying to do, but I would guess he is ‘pivoting’ a broken arbor.

If my assumption is correct, then the answer is ... they didn’t

They made the arbors by turning, and would not have considered inserting a new pivot any more than they would ‘Helicoil’ a damaged thread.

MichaelG.

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Edit: This, from 1910 might be of interest:

http://www.gutenberg.org/files/20317/20317-h/20317-h.htm

Edited By Michael Gilligan on 17/02/2020 07:45:16

Drilled then hardened simples.

Drill with a decent solid carbide drill [Drill services are my favoured supplier atm] or EDM but that wont be cheap.

Tony

That's what I was alluding to,

Anneal, drill and re-harden.

* Danny M *

I think Danny’s post was to try to make CTT think? Continual ‘spoon feeding’ rarely helps development!

Thank you ndiiy.

That was exactly my point.

I was not trying to be rude but just wondering how 18th century clockmakers made tiny holes and maybe CTT should do a bit more homework.

I, for one, would be most interested in the results.

* Danny M *

* Danny M *

DIY EDM

https://www.instructables.com/id/EDM-Electrical-Discharge-Machining/

Robert G8RPI

Edit.This is North American and was connected direcly to the mains supply. If trying this you MUST use an isolation transformer.

Edited By Robert Atkinson 2 on 17/02/2020 10:22:53

carbide tipped, whatever you use

slow speed high torque

must be a stiff setup so a short drill bit

Thanks for all the helpful posts guys. Annealing and carbide drill seems favourite also I have picked up on the centre cutting drill which is important as some drill bits have alternative cutting edges i believe. A point not mentioned here is that the degree of hardness will vary on hardened steel, some is tempered after hardening.

Chris

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Another point still not mentioned, Chris, is what the job actually looks like.

MichaelG.

Edited By Michael Gilligan on 17/02/2020 14:14:30