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 ;)

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.

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.

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

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!

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

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?

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?

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.

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.

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

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

The taig has 9.5" of travel in the X direction, and with the head mounted horizontaly along with a long toolingplate (hanging out over the side of the table on the mill). Still I don't think the motor is powerfull enough, and the machine is probably not rigid enough either. If you are going to step drill up to 7/8 it will take many drill bits which will cost you lots of money (as maxboostbusa has pointed out). If you are just going to make a couple of these, then find someone with a bigger machine.

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 ;)


Although you don't like the idea of flipping the part, embrace the idea. "Another chance for the hole to be off"? Not really. It's your best shot at accurate location from both ends, assuming a centered hole. Whatever your hole is "off" in the center of the part, it's going to be at LEAST 2X that far off at the other end of the part if you attempt to drill from one end. If you *MUST* do it on the mill, I'd drill it from each end with an 11/16 drill, using cutting fluid rather than coolant. Then finish the hole thru from one end with a 7/8 reamer or drill. If you're going to finish the hole with a drill, I'd use a 5/8 dia. drill, as a 11/16 may cause the 7/8 drill to be really "grabby". Plus, a 5/8 or 11/16 standard jobber-length drill will probably get you to the center from each end. Slamming this hole in one shot is not realistic, unless it's a REALLY rough & dirty job.
I also have to vote for a lathe with a 4-jaw. Most drill presses, with the exception of a radial drill, won't have the necessary quill travel.

Good luck with this job! :eek:

Helstrom, I can tell you from experience that the lathe will be the quickest and cleanest way this can be done with bench top equipment.

I had to do a similar job for my tractor where I had to use DOM steel tubing. This is hard stuff to begin with. I had to make bushings for 12 places on the tractor and each bushing had to be anywhere from 6" to 10" depending on the location.

The original material that I had was 1.25" OD and .5" ID size. I had to bore out the tubing because I wasn't buying more tubing to have to ream anyway, just the few thous that it needed for clearance. Not to mention the extra $100 in materials when I already had some. The end result needed to be 1.25" od and 1" Id. Had this been aluminum, it would have been just as easy.

I have a Grizzly g0516 Lathe mill combo and the 9x20 lathe is a really good sideways drill press. :D

The Lathe will have much more rigidity for this purpose and also, you can drill the hole under size and bring the correct diameter out with a good boring bar. Best of all, this can be done without moving the part, or swapping end to end. Even if you did, you could still keep your center with little trouble. A Self centering 4 jaw would be the ticket.

I don't know what your tolerance can be with this job, but if you want a clean hole that is the same size from end to end, skip the drill press. There is not a standard drill press that can give less than .010 run-out that I have seen. Especially at that length, you will be able to tell when it looks all buggered up inside.

If you don't have anyone to let you use their lathe, or someone that can do this for you nearby. I suggest letting some members from here help you. I know shipping that AL is cheaper than messing it up. Much cheaper than tearing up your mill. I suspect that your belt will break pretty quickly even if you can get some way to get the length out of it.

I suspect that if you have a local machine shop, somebody there with much more capable machinery could do this for you for the price of a beer or 2. :cheers:

You could start with a larger piece of alloy, drill and ream in lathe or drillpress.
Then machine outside surfaces to the 7/8" hole.

Thanks for all the advice guys,

I agree that I was a little naive to think that I could drill that deep a hole
with a Taig but I was just hoping that someone out there had actually been able to achieve a similar feet ;)

Anyhow, I guess I'll just have to find a local shop that can do it for me. I will initially be making 3 pieces but maybe more later on, so I would have liked to avoid paying setup and shop fees for this part of my project. Who knows, maybe I will just build a gundrill setup from scratch to suit my needs... that's what you can do with a mill right... build things... lol.

Anyhow, I have an alternative to drilling but just not as simple, basically drill shallow holes at ends and slot out the middle underneath with the mill. On the upside this would reduce obverall weight of the piece :).

Frank

Anyhow, I have an alternative to drilling but just not as simple, basically drill shallow holes at ends and slot out the middle underneath with the mill. On the upside this would reduce obverall weight of the piece :).

Frank

Allow me to throw out another idea: since you can optionally mill a slot in the solid material and drill holes in the end, what about making a multi-piece construction? Use 1.5" x 2" (I think that was your original size requirement) rectangular tubing, which would probably have a .125" wall thickness. Then machine short rectangular plugs with the 7/8" holes to be heliarced or screwed (or even roll-pinned) into the ends of the tubes?

This guy has several different sizes listed for what looks like reasonable prices. Maybe he could get you the right size you need.
http://cgi.ebay.com/Aluminum-Tube-Rectangular-1-x-2-x-125_W0QQitemZ200200987345QQihZ010QQcategoryZ45024QQtcZphotoQQcmdZViewItemQQ_trksidZp1742.m153.l1262

Allow me to throw out another idea: since you can optionally mill a slot in the solid material and drill holes in the end, what about making a multi-piece construction? Use 1.5" x 2" (I think that was your original size requirement) rectangular tubing, which would probably have a .125" wall thickness. Then machine short rectangular plugs with the 7/8" holes to be heliarced or screwed (or even roll-pinned) into the ends of the tubes?

This guy has several different sizes listed for what looks like reasonable prices. Maybe he could get you the right size you need.
http://cgi.ebay.com/Aluminum-Tube-Rectangular-1-x-2-x-125_W0QQitemZ200200987345QQihZ010QQcategoryZ45024QQtcZphotoQQcmdZViewItemQQ_trksidZp1742.m153.l1262

That is a good thought, but The long sides of the rectangle are going to be chamfered by about a 1/2" at a 5-10 degree angle, which will put it through the tube walls, but I may use that concept elswhere in my design. :cheers:

/O\..............\
| |..............| pardon my simple drawing ;)


Thanks


Frank

/O..............
| |..............| pardon my simple drawing ;)


Thanks


Frank

HAHA... ASCII CAD at it's finest! ;)

No charge for the idea. ;)