Making a 1.12" Hole in Aluminum

I have a 4" Diameter by 1" piece of Aluminum that I need to make a 1.18" hole in. This will not just be a one time thing, I will need to do several of these.

My Lathe is a Heavy 10

The first time I did it I just drilled a small hole and enlarged it until I could get my boring bar in and then bored it out. That was pretty time consuming so I am looking for a faster way. I see a 1" drill bit with 1/2" shank is available but that also seems like it might be time consuming, unless I could jump from say a 1/4" hole to the 1" bit, but that seems highly unlikely. Anyone have experience using that large of a drill bit?


My other thought was to get a 1" or 1.12" end mill and use that, but my only problem is holding it. My jacobs chuck can't hold an endmill that large, although I do have a QC toolpost holder for a MT3. (provided I could find a 1" to MT3 End Mill) Would holding an end mill in the tool post or chuck work for making a hole that large? (material turning instead of end mill?)

Thanks

I've done a similar thing, using successively larger drill bits and then finishing with a boring bar. On my 10K, I drill a pilot hole, say 1/4" or so, then go to 1/2", 3/4" and then 1". Your heavy 10 could probably do it in bigger steps. On mine, I have to be careful to not force the bit, but it goes much faster than using a boring bar the whole way.

Blob

Make the pilot hole with a 7/16 or 1/2" bit and then go to the 1", you did say aluminum right? Sharp bit, cutting fluid, and low to med speed to keep the aluminum from galling up, making that jump should be a piece of cake.

I think phantom71 is very likely correct that you can make the 1" in a single jump. Another trick you could try is to grind the 1" drill so it cuts oversize; many times I have found the friction from the lands rubbing is greater than the cutting effort and an oversize cutting drill does not rub as much. It is even possible you could do the 1" in a single pass if you use a split point drill.

You can cheat. Get an old #3 or #4 MT sleeve and weld a handle on it. #4 MT bits are cheap on ebay. Use backgear and keep some pressure while drilling. I have some Armstrong holders that are ages old for just this purpose...Bob

It is pretty standard practice to sneak up on your size with ever-larger drills. But, in aluminum and with a solid grip on the work, there is no reason why you cannot drill your 1" hole from a small pilot hole, say 1/4" or even without a pilot hole assuming you've got a sharp drill. Split point is best for this.

Graduating your hole size is one way to help keep the hole on center. If you just plunge in a 1" drill and you are not certain you've got even flutes, you might push the hole off. Less probable with a shallow depth like 1", but still possible. If you're working with a Silver & Deming drill with a 1/2" shank, see the last paragraph.

If I'm taking a big bite with a big drill bit, regardless of the means of drill mounting, I will clamp a drive dog on the drill shank and rest the bent leg on the flat of the compound to take the torque and prevent possible spinning in the MT2 hole of the tailstock quill.

If you're drilling/boring aluminum, you should be able to use a short/stiff boring bar and hog out about 0.125 DOC per pass. If speed is really the issue, and you're only looking for size accuracy to ten mils, this can be pretty quick.

BTW, I have drilled a 2-1/2" hole in steel on a little 9A using a twist drill with a 1/2" shank. Very scary, the 1/2" shank is just not stiff enough to keep the flutes centered when the drill is trying to seat itself. Once the lips were all the way into the work, things settled down but never tried it again, always used a boring bar.

Ed in Florida

With a rigid setup, a boring bar should be able to do this in short order.
Basically the spindle should be running at top speed, you should use WD40 as
a cutting lube, and the boring bar should be just long enough to do the job,
no longer.

You should be able to take at least 1/4 inch on the diameter per cut.

Jim

Driling the hole

Use what jim rosen is telling you, this is the best and most surest way of performing this task, plunge slowly always being aware of any buildup on the flutes...if you see this stop and adjust your speed or coolant and you will make a very nice hole

I've used a center cutting end mill many times for drilling flat bottomed holes in aluminum and acrylic, but when it comes to drilling a through hole a drill bit does a better and faster job.

A sharp drill bit is a must.

If you end up mounting your drill in the tail stock take a moment to make sure it is aligned with your head stock. If everything is lined up the chip produced by each side of the drill should be equal. If one side of the drill is producing a longer chip than the other something is a little out, which means you are using a bit more "armstrong" than is necessary.

WD 40 is certainly the lube of choice for aluminum

Cheers, Erik

Erik Graham said:

....WD 40 is certainly the lube of choice for aluminum

Cheers, Erik

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You guys who like WD 40 for cutting aluminum should sometime get a can of ATF, automatic transmission fluid, in my experience it works much better than WD 40 just brushed on ahead of the cut or sprayed on.

The WD comes in that handy dandy self-dispensing container!

Trouble with drilling a nearly two inch diameter hole on a lathe that size,
the drill's gonna be tought to keep still in the tailstock.

Jim

I'm getting ready to bore a similar hole,...1 1/16" in a 3" diameter aluminum. However, I will be going the entire length of the 13.5" shaft. I am waiting now for the arrival of the longer boring bar. Longest one I had on hand was only 11.5" I turned the stock down a small amount to true it up. I'm planning to use a 3/8" thick hickory washer I made for a spacer against the chuck. Hope it works.
danny

intrepid said:

.......1 1/16" in a 3" diameter aluminum.....going the entire length of the 13.5" shaft.....danny

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That is a real challenge! I think drilling a starting hole 6-3/4" from each end will be difficult enough, drilling a hole through the entire 13.5" length and then boring this diameter/length combination will be well nigh impossible.

Congratulations ahead of time if you do it.

The through hole doesn't have to be real accurate. There are bearing reseses in each end that I have already cut and the long hole is needed just to pass the shaft through. I know I could bore it from each end, but I am interested in trying my skills and testing the limits of my tools.
danny

thanks for the help guys.

I will try your suggestions and see which works best.

spad bit do it in one pass. no pilot holes. just one 1.18 bit.