Deep drilling in aluminum...help

[Helstrom]

Hi Guys,

I'll be getting a taig CNC machine soon, but I find that I have a need to do some accurate drilling or boring in 6061 aluminum. I need to drill a 7/8" through hole 6" or 8" deep in a aluminum block which is 1-1/2" x 2" X 6 or 8" long . I was hoping that someone might have a suggestion as to the best way to proceed.

I know that the Taig head can be rotated to mount horizontally, but I am unsure if a long bit would remain sufficiently straight when drilling, I would like to keep the accuracy as high as possible and I would like to do it in one step rather than drill half way and flip the stock around it (it's just another chance for the hole to be off).

Has anyone successfully drilled or bored a deep hole like this? Or should I build a jig and bushing and use a drill press?

Your advice is appreciated.

Frank

[The Blight]

7/8"? I'm not even sure the Taig is good enough for the job. My bet is that your motor will stall. You might (just might) get away with drilling out the hole with several different sizes of drillbits, but 6-8" is a lot! When I think about it, I got to say that I doubt it.

I would actually do this on a lathe with a 4jaw chuck or on a powerfull drillpress.

[Helstrom]

Originally Posted by The Blight 7/8"? I'm not even sure the Taig is good enough for the job. My bet is that your motor will stall. You might (just might) get away with drilling out the hole with several different sizes of drillbits, but 6-8" is a lot! When I think about it, I got to say that I doubt it. I would actually do this on a lathe with a 4jaw chuck or on a powerfull drillpress.

I know it would be tricky, but peck drilling seems like it would be possible with a generous amount of cutting fluid. I don't have access to a lathe.

[ataxy]

7/8 is big and will put one hell of a load on a taig even with peck drilling

[bilinghm]

A workable solution would probably be to move up slowly in drill diameter. Start with a 1/16, then 1/8/, 1/4, and on up until you can achieve the full hole depth required. Frequently withdraw the bit completely from the hole to clear all chips. Then proceed with small increments until you can switch to a boring bar or head. A 7/8 " drill will make a pretty lousy hole unless it has been expertly sharpened. A single flute, as used on a boring bar will yield the roundest hole. A better solution is a drill press of at least 1HP with increasing size drills, carefully matching RPM to drill size. Cutting fluid too! Ream to final size.

Good luck!

[emdub954]

Step your drills...and for your final drill "7/8" get one with thru coolant

[cjdavis618]

My advice,

Don't kill the Taig and find someone with a lathe. I know that is a pessimist view, but what would take you hours to step size, peck drill, etc etc. Would take about 10 minutes on a lathe.


Are you having to do just one of these or more?

[Oldboy]

My two cents worth.
Boring Bar is the best. But if your doing a 8" deep bore?
Why not bore 4". Then flip it and bore the other side 4".
Then do a final bore to clean up the hole the full 8".
The shorter you keep that Boring bar the better.
Or you could use a reamer for your final size?

[LeftCoastCNC]

What kind of accuracy are you looking for?

You need a minimum of 12" to 16" of travel IF the Taig could do it. I do not know anything about these machines so I checked out their website and did not see any machines with this kind of travel. The max tool shank dia looked to be .375. A 7/8" X 6" to 8" long drill with a shank that small would be a rodeo. Not to mention the expense to add a tail rotor to the Taig so it does not rotate around the drill (just kidding). You would be far better off using a machine with more power and mass.

[maxboostbusa]

You have to figure in the cost factor of buying extra long bits also. To get good bits and step drill all the way to 7/8 is probibly going to cost ya. Not to mention even if pecking the smaller bits wander off center at any point then it will continue on every other bit to a certain degree. Does a Taig have enough travel in the Z or even the X to position the stock and a long bit? If you had the 6" stock and a 3/8 jobber drill you will probibly looking at at least 10" of space tied up.

If you try it that deep in 6061 I personally would use a parabolic drill at least. Just my 2 pennys though.

[MIKE JEFFERS]

pre-drill 3/8 -10mm ish
long 16mm (5/8") front cutting end mill and interpolate it

dunno if a tiag is rigid enough for that tho

[philbur]

Come on guys how the hell is he going to bore a 6" (or possibly 8") deep hole at 7/8" diameter on a Taig. The nose to table will need to be not less than 12" or even 16". I'm all for "never say never" but this is going a little to far.

Phil