Drill bits, Is it all smoke & mirrors?

[bernard towersParticipant @bernardtowers37738]

Just taken a new 8mm dormer drill (of recent manufacture) and one edge had a positive angle on it and the other a negative, hence the reason I sharpen new drills before use.

[samuel heywoodParticipant @samuelheywood23031]

Just a little postscript.

 

Father presented me with what i took to be a scrap of 1/2″ thick Black MS at Christmas , said he wanted some 3/8″  & 5/16″ & maybe 1/2″ holes drilling in it to make wooden dowels with it.

Got around to it earlier.

750 rpm (about right for MS 3/8″ hole?), plenty of oil , vanilla HSS drills should be fine i ended up with two blunt drills that stopped drilling part way through hole, oh & way more smoke than normal~ guess that should have been a clue really, but i was tired.

So, had to dig out the cobalt ” for special jobs only” ones, that i don’t really like using.~ job finished, skipped the 1/2″ size.

Informed father plate was complete, if a little frustrated with his tough  mild steel.

“Oh, i think it was off a lorry leaf spring (spring steel?)” he says.

me~mutter mutter, would have been helpful knowing that beforehand!

If i’d slowed it right down & i think the hss would have coped, unless someone knows otherwise?

Always pays to know what exactly you are drilling.

[noel shelleyParticipant @noelshelley55608]

Hi Sam,If you have to work on stainless, use a good HSS bit(or cobalt)keep the speed down, use good cutting fluid and keep the bit cutting – if it stops cutting STOP drilling. Stainless is notorious for work hardening. If this happens then only a cobalt or tipped bit will work. You can guess how I know this ! Noel.

PS just looked at my speeds and materials chart, for that job about half the speed you used might have worked.

[Speedy Builder5Participant @speedybuilder5]

As an apprentice, I was “given” a full set of DORMER fractional, letter and number drills from the stores and in return I had made an exceptionally fine picnic table for a certain storekeeper!!  Now 50plus years later, I still use those sets for fine work and some cheapo “tin” plated metric drills 1-10mm x 0.5 for rougher work.  I have to admit that the tin plated ones have stood up to the rough work surprisingingly well.  Added to that a set of 14 – 20mm from Aldi.

By contrast, I bought a full set of metric drills from a “quality” UK supplier which were incredibly brittle and only any good for drilling holes in wafer biscuits!

I am afraid that it is a bit of a lottery and you have to decide if you are going to invest in a good full set or keep on going for the “bargains” – and suffer the consequences.

Bob

[DiogenesParticipant @diogenes]

With ‘anonymous’ steel, particularly donated material, I make a quick visual assessment, has it been cut with a band/hacksaw, TCT cut-off saw, or a grinder, if there are little stubs at the end of the cut, has/is the material been torn / deformed / shows plasticity or has it fractured etc..

If it’s been cut with a grinder, hard steel can often look silvery or ‘polished’ by the wheel, whilst softer material stays a duller grey – tho’ as we know there’s 50 shades between..

If in any doubt, quick investigation with a file will usually tell you all you need to know before committing other tooling.

 

[Michael GilliganParticipant @michaelgilligan61133]

< Pedant Alert >

In light of the [getting a little heated] discussion on the concurrent ‘BBC’ topic … I feel obliged to mention that there is a very big, and significant, difference between ‘tin plated’ and TiN coated.

Tin and Titanium-Nickel are are not descriptions of the same thing.

Plating and coating are not descriptions of the same process.

MichaelG.

.

Edit: __ in a wry footnote ..  it’s easy to see how linguistic standards can slip … check the URL : https://www.wallworkht.co.uk/content/tin/

🙂

[Thor 🇳🇴Participant @thor]

Michael, isn’t TiN Titanium Nitride, gold coloured coating on drill-bits and milling cutters?

Thor

[noel shelleyParticipant @noelshelley55608]

I go with Thor on TiN !  Noel.

[Michael GilliganParticipant @michaelgilligan61133]

Yes, Thor … that was my point

…. I made it after reading Bob’s post: but unfortunately made a typo of my own !!!

MichaelG.

[Michael GilliganParticipant @michaelgilligan61133]

< blushing footnote >
.

As I have mentioned previously:

Pedantry only works when you’re right

MichaelG.

[Thor 🇳🇴Participant @thor]

No problem Michael, I can’t write a single line without making typos, you are usually right.

Thor

[Nicholas FarrParticipant @nicholasfarr14254]

Hi, and of course not to get confused with bronze coated ones either, page 66.

https://5wyuco84ao39w9tsgkkmnmx.blob.core.windows.net/cms/DORMER_PRAMET_Holemaking_Catalogue_2021_EN.pdf

Regards Nick.

[VicParticipant @vic]

I’m fortunate to have a discount store near me. They frequently sell “odd” size drill bits like 6.8mm and 6.9mm long series etc. They are invariably German made HSS and I’ve had no quality issues with them at all so far. The prices are very good as no ordinary budding DIY’er wants drill bits in these sort of sizes! 😆 Sadly (as I work in metric) they’ve started stocking more imperial sizes but these are ok for rough drilling.

[Michael Gilligan]

On Michael Gilligan Said:

Yes, Thor … that was my point

…. I made it after reading Bob’s post: but unfortunately made a typo of my own !!!

MichaelG.

At least 50% of my typos are “auto corrections” made by my iPad. Still my fault as I should check more closely before hitting submit. Sadly this site doesn’t have “preview” like most others which is very helpful in preventing these type of errors.

[Author]

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