## Mill cut geometry?

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?

2. Senior Member
Join Date
Sep 2005
Posts
179

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.

3. tattoomike68 Guest
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

4. Senior Member
Join Date
Jul 2001
Location
Green Bay, WI
Posts
2,380
Ron, You got it !
Leave the rotary table flat.
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

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.

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