Drilling a Deep .680 Hole with Think Ouside Wall

[blackwolf4278]

Hi Guys, I wanted to ask if anyone might advise me on how to properly machine a ID with the following paramaters:

OD Size: DIA 0.8"
ID Size: DIA 0.68"
Depth: 3.8"
Mat'l: Aluminum 6061

So this leaves me with a thin wall and a long cut. I've tried doing it on a lathe but the finish was crap, one time it was okay the second it was horrible with no noticeable pattern, so then I tried it on a mill with better results and the part was "acceptable" - but by no means nice.

So the way i do it on the mill:

Spot Drill
Then 43/64 Drill .1 Peck at 650 RPM and 5 Feed -> Which works fine.
After I interpolate a .625" DIA Endmill in there in order to get rid of the drill point, works okay but very loud.
And finally I Ream with a .680 HSS Reamer at 260 RPM and 1.7Feed and it very loud at some point and the finish doesn't look pretty at all.

Would anyone have any suggestions?

 

[MaxPrairie]

Is this a roller? Start with 1" round, drill your hole then machine OD between two centers.

Edit: I would run the reamer about 850rpm and 15-20 ipm. If it's a manual lathe, slower...

 

[blackwolf4278]

No there's actually more to the part.

Its as follows:

Top OD DIA 1.97" for 1.44" than OD goes to DIA .8" for another 3.82" and final OD is 1.25" DIA for another 1"

As well I do this on a Mill(you said lathe)

Part looks like this:


|***************|
|***************|
|***************| This OD is 1.97" by 1.44" long
|***************|
|***************|
|***************|

____|*******|
____|*******|
____|*******|
____|*******|
____|*******|
____|*******| This OD is .8" by 3.82" long
____|*******|
____|*******|
____|*******|
____|*******|
____|*******|

_|*************|
_|*************|
_|*************|
_|*************| This OD is 1.25" by 1" long
_|*************|
_|*************|

 

[CITIZEN F16]

The first thing you need is good quality 6061, do you have that?

 

[MaxPrairie]

No there's actually more to the part.

Its as follows:

Top OD DIA 1.97" for 1.44" than OD goes to DIA .8" for another 3.82" and final OD is 1.25" DIA for another 1"

As well I do this on a Mill(you said lathe)

Part looks like this:


|***************|
|***************|
|***************| This OD is 1.97" by 1.44" long
|***************|
|***************|
|***************|

____|*******|
____|*******|
____|*******|
____|*******|
____|*******|
____|*******| This OD is .8" by 3.82" long
____|*******|
____|*******|
____|*******|
____|*******|
____|*******|

_|*************|
_|*************|
_|*************|
_|*************| This OD is 1.25" by 1" long
_|*************|
_|*************|

Yeah…I don’t see a benefit to doing this on a mill. Drill a 1/4 or 5/16 hole then go to the bigger drill. Keep the part and tools cool. Ever tried to machine bubble gum?

 

[hvnlymachining]

Sounds like a chip weld problem. If you can get live coolant, that will make a lot of difference. If not, break out the squirt bottle. Give a couple different fluids a try until desired results are achieved.

Good luck.

 

[blackwolf4278]

The first thing you need is good quality 6061, do you have that?

How do i tell if its good quality? Certifications?

 

[blackwolf4278]

Yeah…I don’t see a benefit to doing this on a mill. Drill a 1/4 or 5/16 hole then go to the bigger drill. Keep the part and tools cool. Ever tried to machine bubble gum?

I've tried it on a lathe, as I originally mentioned the finish would come out very bad once in a while and it had no pattern. Its a long hole that has to be turned with a small BB

 

[blackwolf4278]

Sounds like a chip weld problem. If you can get live coolant, that will make a lot of difference. If not, break out the squirt bottle. Give a couple different fluids a try until desired results are achieved.

Good luck.

That would be awesome, but none of my machines have the capability.