Mill cut geometry?

[Ron LaDow]

I need to cut a taper into an existing straight hole, the taper centerline being, say, 6* deviant from the hole centerline. The taper is, say, 14* included angle.
The existing hole is 32mm (~1.25) and the cut surface is probably 1-1/4" long at most.
Material is cast Zn.
So this is easy enough with a CNC, but I've got a vertical mill and a rotary table. Looks like I need to tilt the head and the rotary table?

[greywynd]

Is your * meaning degrees?

So the existing hole isnn't true to the centreline of the tapered hole you wish to create?

If I'm understanding things right....and it's a 'fussy' situation, I would tend to leave the head square, clamp the part to the rotary, get everything shimmed, clamped, etc. to get the hole centreline where you want it to be. I would then strongly suggest a 7 degree taper cutter to mill the taper of teh hole....this would be a fair bit more accurate then trying to tilt everything.

Depending on the part, it might be a possible job for a 4 jaw chuck on the lathe, and use the compound or a taper attachment to create the taper.

Give us more details, maybe we can suggest a better method for what you are trying to do.

[tattoomike68]

the easy way is to blast a big strait hole in the part and press in a tapered hole sleave made on a lathe. weld it in if you need too.

easy as pie

[Rich Carlstedt]

Ron, You got it !
Leave the rotary table flat.
Tilt your head to match the desired taper.
Just remember (!) , the cutter MUST be on the centerline when cutting. If you move the table(& Saddle ) on the Y axis, that is in or out, You will change the taper from the desired angle to another!

No Math Approach
As a help, if you have the pin to fit the hole, and it is straight on its shank, you can bore a hole ( W/Mill) to fit the straight shank in a piece of scrap, then indicate the taper with a dial indicator, untill the head is tilted to match the taper

[Ron LaDow]

greywynd,
Yes, the *=degrees. Even with a taper cutter, I still need to tilt something since the centerlines aren't parallel. They intersect ~ 2-1/4" below the top surface.
tattoomike68,
Can't. There's very little metal around the existing hole and it's zinc.
Rich,
Gave it more though and I think I have to tolt the piece on a flat rotary table.
Thanks, guys, time to make some tools or chips and see what happens.