Micro drilling

I need to drill a wire gauge hole in a piece of brass rod. I have faced off the rod and polished with 300 emery to ensure there are no blemishes. How do I accurately "spot" the rod to ensure the drill bit drills true,and are there any other tips around.

How big and how deep? I have got down to 0.2mm using a 0.5mm centre drill for spotting.

What wire gauge as 10swg is not exactly small?

I drilled 0.3mm the other week, faced, small spot drill and then in with the 0.3mm bit.

Is the hole to be in the centre of the rod - or somewhere else?

Yes,the hole is in the centre of the rod,similar to the set up of JasonB's photo. I don't seem able to get the spot drill to form a sharp enough recess to stop my micro drill wandering all over the place.

Having reread Roger B's post I think I need a smaller centre drill.

You can get centre drills that are really small.

ASA00000 has a 0.25mm pilot.

However you should find that micro drills will go right down a small Jacobs chuck so you only need a couple of mm protruding. It's amazing how stiff this makes them. Usually stiff enough to form their own centre. Once this has been done the drill can be withdrawn sufficiently to drill to required depth.

regards Martin

Have you checked the points of your drills with a magnifying glass? The first cheap micro drills I bought had non existent points. The Titex ones I am now using are excellent.

Hi all

Centre drills are not ideal for spotting holes and they get less ideal as the hole gets smaller ( for example, the pilot gets very fragile.)

Better to use spotting drills - made for the purpose, with much stronger points and they are available in a wide range of sizes down to very small.

For example, "Kyocera" , a Japanese company, list them as small as 0.005" diameter (on an eighth-inch shank) and since you only need to use the point these would probably enable one to make a spot of only about 0.001" diameter if that was needed. Need good bearings in the drilling machine though!

Google "Micro spotting drills" Not sure about easy availability but someone will stock small spotting drills in the UK.

Rod

I tend to use the Americam Keo brand spotting drills, 1/8" one started that 0.3mm drill in the pic above OK. They have a smaller "flat" than other makes. Keo in the front. I only use Ctr drills where the 60deg seat is needed.

May be a bit late in the day Roger but ...

I'd use the tool post instead of the tail stock chuck, while shaping a HSS tool bit with very acute ‘clearance’ angles. Alternatively, grind off half a (scrap) drill and fit that into the tool post.

I've never used a graver, but that could produce the necessary conical concavity.

Sam

This is an alternative way;

**LINK**

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Very simple process ... See the short sequence starting at 1min 30sec, here: **LINK**

https://m.youtube.com/watch?v=4jTKNLjLrNM

They're demonstrating carbide gravers, but a good steel one is adequate.

MichaelG.

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Thanks for that link, Tim

MichaelG.

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I see that the price of the plan has increased somewhat

That looks so far out it isn't true (as they say).

Perhaps it is the camera angle or something

Another gem of yours Michael! That's just how I imagined.

Where do you find them?

Sam

A great link too Tim. Thank you.

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'Eternal Tools' is a regular advertiser in the Horological Journal and I just followed my nose one day.

It's a nice little demo, so I remembered it.

MichaelG.

Thankyou everyone, problem now fixed. I followed Martin Kyte's instruction re spotting,worked perfectly. trued up the point on the micro drill,ensured that there was no play on the brass rod and bingo,a nice clean hole.

Thanks everyone.

Although largely intuitive to many of us, it is worth mentioning in this context (and for lathe work in general), that the stiffness (resistance to bending) of a round bar, projecting from a chuck (cantilever style) is nonlinear in relation to both its length and its diameter.

Although more complex when considering for example a fluted drill, the stiffness of a round bar relates to the cube of the length and the fourth power of the diameter.

Put simply …

Halving the length (overhang) increases the bending resistance by eight times.

Halving the diameter decreases the bending resistance by sixteen.

I'm pleased to know Roger, that your drilling project was a success.

Regards,

Sam