Axis-following in drilling

i did about 3 years ago..but the link now goes to a youtube page that says private video with no info on who it was or anything ..and no way of watching the vid

all i remember the link was from a watchmakers lathe video promotion...was an excert

and i think the lathe was a taig

all the best.markj

this is the guy that had those vids up there

you'll have to ask him nicly to put them back again

all the best.markj

--I remember that; I think it was called "picking the center" or something similar; try searching that string?

In article , Peter Fairbrother writes

Peter,

Probably not relevant to your needs, but oil well drillers do it all the time, with a variety of means, limited only by the flexibility of the drill pipe. See, for example:

but I'm sure a search would give more comprehensive expositions, with pictures.

David

The message from David Littlewood contains these words:

Peter, Drilling the axis of steel arbours is quite a common practice in clock repair work. There are various tecniques, I am no expert but I have drilled down to about 0.6mm hand held using a flag in a wathmakers lathe. I don't thing you would get far if you try to go of the axis with small diameter drills, as the flexing of the drill would soon break it. If you have a look at

he shows some clips, from his clock repairing videos, one of the clips shows how to use a flag. Hope it is of some interest. Bill Lamond

Ive done it using a pinvice and a no 80 drill to drill a hole down a 2 mm stainless steel pin on my Myford using a collet to hold the work . I just used a graver to make a small center in the pin. Then you place the drill into the center and use hand pressure to drill the hole , just pecking away at the hole until you get the desired depth. Yanks call it "peck" drilling. Never tried to steer the drill though, I reckon it would breal pretty quick .

Kev.

That's break not breal.

Thanks Bill, and Kevin, David etc too. Shame the video cuts out just before he starts drilling tho'!

I was trying to convince someone that it actually worked, and the drill follows the axis of rotation of the rotating workpiece.

He thinks that "Unless you invoke some sort of inertial effect, there's no difference between the rotating and non-rotating frames of reference."

He's wrong of course. If the part is rotating rather than the drill then when the drill goes off the axis of rotation of the part the "outside" of the drill tip will be cutting faster than the inside, and good tip design and careful speed control can make this force the drill back to the axis of rotation of the part.

The really interesting bit is that for long curving hole paths it might be possible to steer the drill (slightly) by varying the axis of rotation at the point where the drill was cutting, using a CNC rotating machine of some sort.

I don't know how tight the curves you could get might be though; you'd need a flexible drill shaft and a carefully designed drill tip shape to get anything more than a slight curve.

-- Peter Fairbrother

In article , Peter Fairbrother writes

Peter,

Looking at the example of downhole well drilling, how about a flexible shaft passed down the bore of a curved sheath. The curvature then would depend only on the flexibility of the flexible shaft. You would probably have to push the sheath rather than the shaft, with a very short blacksmith's type drill pushed on its shoulder by the sheath. Would require damn good lubrication though, and have a short and possibly exciting life.

Do you have any specific application in mind, or is it just academic interest?

David

The real trouble with small hole drilling in the lathe is that the top lathe speed is nothing like fast enough.

Shows the device I use. It's small PM dc motor housed in a steel sleeve and fitted with a pin chuck. A 5/16" spigot on the rear end slides freely in a 1/2" OD brass sleeve which is gripped in the tailstock chuck.

It's nominally a 12v machine but it happily runs from a 36v supply at 18,000 RPM and this takes a lot of the pain out of small hole drilling.

Jim

It took me a while to appreciate that it is essential to rotate the part rather than the drill to get the hole to run centrally. Like many such arguments it was easier to visualise the effects by exaggerating the angular difference between the work and the drill. I now understand that with a stationary part and a rotating drill the axis of rotation is the axis of the drill; while with a rotating part and a stationary drill the axis of rotation is different to the axis of the drill hence the drill tends towards the centre line.

Cliff Coggin.

--Oh hey that reminds me: here's my own high speed drilling rig. I replaced the standard chuck with a Jacobs #0. The job was to drill a bunch of #55 holes in some tiny parts for a customer..