Tapered Holes

[Magnum164]

What is the best way to machine an ID hole that has a slight taper? It needs to be as smooth as possible as the tumbler media will probably not be able to finish it like I want.

Material is 7075 AL

Hole size is .485 tapered to .378

[ErnieD]

What is the distance from the large end to the small end or how thick is the
material or how deep is the hole?

Ernie

[Magnum164]

Forgot those Ernie...

Hole depth is .5 .. wall thickness will be .075 at the .485 dia.

[TXFred]

The best way: Chuck it up on a lathe, bore it, then use a toolpost grinder to finish it.

The best way on a Tormach: You could grind the taper as above if you have a fourth axis. You will need to set the axis at the same angle as the taper.

Frederic

[ErnieD]

Am I correct in assuming then, that we are talking about a cylinder that is .635
in diameter and .500 long with the tapered hole in it?

Ernie

[Magnum164]

Am I correct in assuming then, that we are talking about a cylinder that is .635
in diameter and .500 long with the tapered hole in it?

Ernie

Pretty much.....yes

[Magnum164]

The best way: Chuck it up on a lathe, bore it, then use a toolpost grinder to finish it.

The best way on a Tormach: You could grind the taper as above if you have a fourth axis. You will need to set the axis at the same angle as the taper.

Frederic

The tapered hole is the ID, not the OD.

[Magnum164]

Am I correct in assuming then, that we are talking about a cylinder that is .635
in diameter and .500 long with the tapered hole in it?

Ernie

But let me add, it is a boss on the end of a 2.5IN OD Round. So the wall thickness will not be much of an issue as I can always remove that after the hole is tapered...

[btu44]

Maybe a setup like this would work?

http://www.cnczone.com/forums/tormac...cal_lathe.html

[Magnum164]

Maybe a setup like this would work?

http://www.cnczone.com/forums/tormac...cal_lathe.html

I am contemplating doing that for other parts, but I do have a lathe. But I don't remember anything in that post on doing a tapped hole, just thru holes.

[TXFred]

The tapered hole is the ID, not the OD.

That's what I was picturing. "Hole" generally implies that it's got an inner diameter.

You can grind an inner diameter, given a small enough stone. In this case, you could mount a Dremel tool in the toolpost to do the grinding.

Frederic

[Wog]

I would use the forth axis or even a basic rotary table mounted at a 6.1 degree incline. Would a 3/8" (max. diameter) 4 flute end mill leave too rough of a finish?