method for drilling/cutting/milling conical holes?

[whatwastold]

Hi, I'm after a method for drilling smooth gradual conical holes in to either brass or SS. The closest I’ve come to in my research has been with the use of a drill bit called a “step drill bit”, which isn’t really designed for the purpose, and also however would leave me with a stepped conical hole and what I’m after is a smooth gradual incline.

Is there such a mill bit capable of this task?
Is this possible with a 1HP drill press if I go really slowly?

The reason I’m investigating this is due to the fact that we have low water pressure at an out let, so hence I’m designing a conduit fitting which will increase the flow rate. I know you can buy such devices, however that’s no fun whatsoever.

[graemet]

When you have your new lathe, use a boring bar with the topslide set on the angle you want the taper.
Cheers
Graeme

[Mick C.]

Try here, am sure this is what you are after.

http://au.farnell.com/jsp/search2/br...01+401+1002027

If you are trying to profile a venturi or some such shape into a tap housing etc maybe it would be much easier and perhaps a lil more efficient to just do it free hand with a die grinder... But i'd try to model it first with plastersine.

[soundman]

Depending on what you want to achieve there are a couple of solutions.

Cone cuts, are like a step drill with no steps, just a conical drill, like step drills they are intended mostly for sheet metal work so deep holes are a bit of an ask.

Tapered reamers, one drills a hole & then reams it out with a tapered reamer.
there are two types I've seen, a sheet matal work type available from dick smith & jaycar intended for enlerging holes in sheet matal
And the machinist type for reaming tapered fits like morse & similar tapers.

or have it turned in a lathe.

if you have a flow restriction in water pipe the overriding factor is diameter, the relative quality of the transition is not as significant as you may think.

small diameter pipe will suck the guts out of your water flow much faster than a single point restriction, the quality of a single transition is far less significant again.

cheers

[whatwastold]

I think Ill go the lathe route – good first (real) project, get accustomed to using a bore bar and see what I can come up with. There’s no point in paying for things like step-drill bits and tapered drillbits or conical reemers without using what’ll already be on-hand. Should be a fun learning experience.

Farnell’s a great site by the way, been there many-a-time. It always amazes me what can be found there, however tapered drill bits was far from expected so I didn’t bother looking there – proved wrong once again.

Anyway thanks all, your knowledge humbles me.:eek:

[rodm]

I would try face and edge cuting before venturing into tapered boring. It is not that difficult but for your first project it might present a few problems.

Use a tool where you can see what is happening and get used to speed and feed rates. Listen to the sounds and you will know when it is going right and when it is not going so well.

A boring bar hangs out of the tool holder more than other lathe tools so is more prone to flexing which will push it below the cutting line and it will dig in. Graeme has given you the right technique and remember to use the top slide handwheel. If you use the carriage handwheel you will be making a straight cut and things will go very wrong for you at this point. The AL-50 needs a modification to the toolpost clamp plate to make it suitable for deep boring and serious cutting and we can point you in the right direction when you get your machine.

I don't want to leave you with the impression this is a difficult thing to do but IMHO it would be best to do some face and edge cutting first.

[whatwastold]

I tend to agree with your sentiments rod - as I've only just discovered what a boring bar is.