Need to make a big hole in Aluminum plate

[Investigator]

I need some suggestions please, I need to 'bore' a 2-2.5" hole in 1.5" aluminum plate.

I'm working on a steady rest, my lathe didn't come with one. To that end I have acquired a piece of 1.5" aluminum (6061-t6 I think) which is 6x10", as well as some brass 'fingers' for the rest. I have pretty much worked out the steps I need to do everything but make the 'big hole'. I have a 12" Logan lathe and a RF30/31 mill to work with.

I think what I need to do is drill then bore it to size on a mill. Trouble is I have no boring head or tooling. Is there another way? Or do I need to bite the bullet and buy a boring head to do it?

Scott

 

[David S]

Let me be a bit crude, but could you drill a series of holes around the circumference of the hole and then cut out with a jig saw, and finish in the lathe?

David

 

[benmychree]

Get someone to water jet cut it, they could shape the whole works for you.

 

[Dave Paine]

The drill holes and use jig saw method of David S. could work, but you need to go slow with the jig saw. I tried using my jig saw on some 1/2in aluminium and within seconds the blade gullets were filled with cold weld particles. I had to pick these out one at a time then go much slower.

Another option is to grind a trepanning tool.

A Tom Lipton (Oxtool) video on this topic.

Tom Lipton video on trepanning tool

 

[Investigator]

I don't think turning the piece itself on the lathe is an option, at least not the way I am planning on making it. I could possibly make a tool on the lathe to cut the hole in the mill though.

The drill and jigsaw idea would likely work, but I'd rather do a more elegant and precise method if it's available.

 

[benmychree]

The drill holes and use jig saw method of David S. could work, but you need to go slow with the jig saw. I tried using my jig saw on some 1/2in aluminium and within seconds the blade gullets were filled with cold weld particles. I had to pick these out one at a time then go much slower.

Another option is to grind a trepanning tool.

A Tom Lipton (Oxtool) video on this topic.

Tom Lipton video on trepanning tool

One should always use a lubricant to avoid chip welding with aluminum; kerosene is the old standby but Magic Tap works well and is not so smelly.

 

[GoceKU]

Scott, the simplest way i can think off is to go to a friend or a fellow machinist with a bigger lathe that can swing the whole piece around, drill and thread the centre of the hole then attach it to a mandrel and use an parting and grooving tool to part it off, for aluminium hand ground hss tool should be fine https://www.sandvik.coromant.com/Si...arting-grooving/face-grooving-tools-thumb.jpg

 

[Investigator]

Thinking off the wall here.....

I have a small rotary table. What about mounting it so that I could turn it under the mill head, and cut with an end mill?

 

[DAT510]

You could also use a hole saw, though the surface finish won't be the greatest. Drill/Hole Saw then boring would get you the nicest finish. If you get a boring head for your mill, as long as it doesn't have a fixed arbor, there are a variety of additional uses, such as a ball turner or as a means to further offset your tail stock, that you can use it for.

 

[benmychree]

That could work, (doing it on the rotary table) but likely you'd need to cut from both sides due to the thickness, same would go for trepanning. A hole saw is a option, also going at it from both sides.