Drilling 0.5mm Extruder Hole on a Lathe.

I am doing a DIY Engineering evening Course at Eastleigh College which is great fun and
very informative. Can't wait to start making my own stuff.

We are taught to use a starter tool before drilling a hole on the Lathe. Now my question is do people
use a starter hole when drilling the 0.5mm hole for the extruder.

If I first drill out the barrel then I don't think my 0.5mm drill bits will then reach. If I go
for the short route then I am sure I will be told to use the starter tool again.

i.e. Does the use of a starter tool matter for the 0.5mm hole. Is the extruder okay
with the 0.5mm hole having like a counter sink type hole made by a starter tool.

Or can you get starter tools for very small holes.

Thanks : Keith

Edited 1 time(s). Last edit at 11/01/2010 06:10PM by KeithSloan.

Unless you have very good control of the depth on the center drill, just forget it. Make sure the drill is centered, use an indicator to check the tailstock, or set a tool in a holder. With .02" diameter holes, a couple thou makes a difference. Also make sure that there isn't a sharp tip, take a facing pass with a well centered tool to ensure a tiny flat for the drill to start on.
I used my mill to drill the holes with no spotting bit and had no issue whatsoever. I also did .3mm holes and I'm sure I could go smaller. Just take you time on the setup, as I said every thou is a significant percentage of the hole you are trying to drill.

Watchmakers would create a tiny divot on the center of the stock with a graver, and then use a micro drill bit held in a pin vise. All by hand, no tailstock! I saw a video of this technique on youtube long ago but unfortunately cannot find it...

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[haveblue.org]

Have Blue is right, you get more "feel" that way, get yourself comfortable and calm, no rush.

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Random Precision

I pecked it with a #00 center. The drill diameter is .64mm on a 00 IF you get beyond the center drill's lip. The goal of a center drill is to provide a place for the drill bit lip relief to fall into so they can't (ideally) wander.

If you still have a small counter sink - part it off (or use whatever operation of your choosing to get your final shape).

I'll second the comments about careful setup.

... you can use another thicker (more solid) drillbit as starter, then drill your 0.5 or 0.3mm hole and then grind the tip flat or slightly conical, so you won't have a cavity around the hole ... and last clear the hole with the thin drillbit again ...

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Viktor
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The technique with a graver is called "catching the centre". I had a link to an excellent video on my blog, but for some reason the video has become private. Here is another one though: -

[www.youtube.com]
[www.youtube.com]
[www.youtube.com]

Edited 1 time(s). Last edit at 11/02/2010 05:25AM by nophead.

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[www.hydraraptor.blogspot.com]

Hello,

I make my nozzles by using the smallest center drill, that I could find (#000, I think), and making a small indent in the center of the nozzle tip. Since the center drill is so small, your tailstock must be properly aligned or else you will break the center drill. On a standard engine lathe, you can make the indent easily by going slow and paying close attention. (On the turret lathe, I use a stop so that I can't go too deep.) You may still go too deep. This is not a problem.

After the indent is made, I use a pin vise and drill the orifice by hand. Once the orifice is drilled, I face off the tip of the nozzle in order to make it look nice as well as remove any slight "bowl" created by the center drill. I usually take off around 0.008 when facing off the tip.

Regards,

Brian

Thanks nophead! I think I had seen that original video via your site in the first place - good to see that there's another video of the technique.

I haven't tried making my own yet, but I'd be inclined to also use the facing technique as others have noted.

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[haveblue.org]