Making a series of 1-3/8” holes....

[Firstgear]

I need to make a series of 1-3/8” holes in aluminum that is about 1/8” thick....what is the best way to go about putting a series of holes in the aluminum plate? I plan on using my mill.....anyone?

 

[darkzero]

Depends on the accuracy of the holes you need. Drill only, drill & ream, drill & bore, annular cutter, etc.

 

[Cadillac]

How many in the series? Annular cutter would be quick and accurate

 

[Firstgear]

Just need to be able to put a grommet in each hole.....no more than 10 holes....maybe fewer.....

 

[darkzero]

In that case with only being 1/8" thick, I'd use a Uni-Bit/step drill. Preferably a step drill that is larger than the hole size you need cause you can use the next size up to chamfer one side of the hole right after you drill the size hole you need.

 

[tjb]

I have another post running right now on a similar issue: milling a series of 1", 1 3/16" and 1 3/8" holes in 1/4" acrylic. Don't know how to link it here, but it's titled 'Annular cutters or drill bits?'. Got a lot of good responses and recommendations. You might want to look at that thread. I opted to try drill bits first, and I purchased Silver & Deming drill bits for the 1 3/16" and a 1 3/8" sizes (already had one for 1"). On a completely stand alone basis, that was not my first choice - based on all the responses, I would have purchased annular cutters. However, I have had several occasions in the past when it would have been nice to have drill bits that size. So I rationalized trying them first. If they worked, fine; if not, I'll get the annular cutters but still have the drill bits on hand if I ever need them in the future. About 2 hours ago, I finished milling twenty-one 1 3/16" holes in 1/4" acrylic. The results were amazing! I tried an experiment on scrap by milling in one pass - no pilot hole. I set the power quill on its slowest feed rate, and milled at 600 RPM's. There were no chips or cracks, so I milled the final pieces like that. All 21 turned out beautifully. I'm a happy camper.

I suspect you could expect similar results in 1/8" aluminum, but you'd probably need to modify the method a little. First, I did not use a backing piece on the acrylic. My strips are long and narrow, so I simply blocked them up in the vise and drilled straight through. To hold a piece of 1/8" aluminum stock securely, you may run into a crimping issue (maybe not). Second, I think I'd be more inclined to start with a pilot hole on aluminum. Probably not a big issue, but there'd be a little more chance of wandering and/or grabbing in aluminum than acrylic. Finally, regardless of what tool you use, I would suggest using the power quill. A few days earlier, when I was milling the 1" holes, I started by trying to manually feed. You just can't get enough control that way on something as delicate as acrylic and, I would suspect, thin aluminum. If you have a uni-bit that runs up to 1 3/8" as Darkzero suggested, that would simplify the process somewhat (there's your pilot hole), but you'd need to be especially sensitive to the bit grabbing the aluminum.

Good luck. Hope this helps.

Regards,
Terry

 

[Firstgear]

I have previously drilled into 1/8” aluminum and put it in my mill vise with parallel plates and have had no problem drilling into it. Now haven’t done anything as large as 1-3/8” so that might be the challenge.

I recently moved my new horizontal band saw from the back of the truck and I found some materials that I had bought at an auction many years ago. I found some aluminum angle as well as some big pieces of aluminum box, again they looked like 1/8” thick. I have new aluminum 1/8” plate, but I might use the box. Only downside is that it looks like it might have been stored in a barn or outside so it needs a slight clean up cut which will only make it thinner....ugh!

 

[tjb]

I have previously drilled into 1/8” aluminum and put it in my mill vise with parallel plates and have had no problem drilling into it. Now haven’t done anything as large as 1-3/8” so that might be the challenge.

I recently moved my new horizontal band saw from the back of the truck and I found some materials that I had bought at an auction many years ago. I found some aluminum angle as well as some big pieces of aluminum box, again they looked like 1/8” thick. I have new aluminum 1/8” plate, but I might use the box. Only downside is that it looks like it might have been stored in a barn or outside so it needs a slight clean up cut which will only make it thinner....ugh!

I hear you on drilling into 1/8" aluminum. I've never tried anything as large as a inch+ bit on aluminum either, but it's a piece of cake on smaller sizes.

What is the orientation of the piece you're milling? My 21 holes were on three separate strips of acrylic that were 1 5/8" wide. The narrow shoulders made for some delicate setup, but other than that, it wasn't an issue. Depending on your layout, another option you might consider is using a rotary table. Clearly, more time-consuming, but if you have a rotary table and don't have a bit or annular cutter, it may actually be more efficient. A few years ago, I needed to mill a series of 16 holes (about the same size we're talking about here) in a 5-6-5 pattern on a rectangular piece of 1/4" aluminum. With the rotary table, it was not possible to index the cuts - every one needed to be indicated individually - so it was not user friendly, but the result was fine. In the grand scheme of things, I finished the project sooner by using the rotary table than if I had played the waiting game on getting a bit, etc., etc.

Let us know how you come out.

Regards,
Terry

 

[Firstgear]

Yes a pattern of 5-6-5 or 4-5-4. About 12-13” long and either 6 or 8” wide if I use plate or 4” wide if I use the box section. I have materials in all cases....I have a rotary table on order, but hasn’t arrived yet.

I ordered up an annular cutter.....

 

[GrayTech]

+1 for the step drill bit. I did 80 holes in ⅛"aluminum varying from ¾ to 1⅝. Step drill did a great job. Sometimes we over think and complicate things.
As for cleaning up the aluminum, very fine sandpaper on a sanding block will make quick work of that. No need to cut it unless its dinged up.