quickest way to bore a large hol using a lathe

I have a 100mm dia round piece of aluminium that 10mm thick. I need to bore a 80mm hole

What's the quickest way to do this?

Trepane to just under 80mm then finish with a boring bar. Holesaw would be another option to remove most of the material.

J

Another option, rotary table and milling machine.

Trepane? Whats that

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Similar to this ... but the metal-worker's version.

MichaelG.

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Edit: there's some useful info here

Edited By Michael Gilligan on 16/05/2014 08:23:28

Have a look part way through this post where I did it to some 6" discs, cut about 4.9mm from either side and knock it out like I show.  Use a tool a bit like  aparting tool but with some clearance on the outside edge It has the bonus of giving you a usable disc from the middle.

This one shows the tool a bit better, on deeper cuts I move the tool across the cut slightly as I go to help keep some clearance, this is 5/8 material moving the tool about 0.020"

Edited By JasonB on 16/05/2014 08:27:33

Hi Petro1head, I used a holesaw to cut the middle out of an old lorry piston blank that I'd previously cut off. It was only about 60mm diameter, but I had to cut as deep as I could from one side and then turned the blank around and finish the cut on the other side as the blank was about 25mm thick to the high point. I removed the pilot drill in the holesaw and cut at a faily slow speed with plenty of cutting fluid. Once cut it gave me a usefull blank without a hole in it.

Regards Nick.

Hi All

About hole saws......

A hole saw is normally fitted started with a drill that drills and centres the saw at the same time, however the drill is fairly weak compared to the lateral forces imposed by the hole saw, allowing it to jiggle.

If you fit a solid piece of steel Ideally high tensile steel in place of the drill in the hole saw, and pre drill the centering hole, and then lubricate the pre drilled hole well prior to making the hole with the saw, you will find the finish achieved by the hole saw is better.

Hole saws are not all created equal the sizes are nominal at best. If you have several saws the same size they all will be slightly different. Do a test hole to see if it is right for your job.

When drilling deeply into material the teeth will clog very quickly, particularly with aluminium, you have to withdraw the saw very often to clear the swarf built up in the gullets of the teeth. if you don't it will jamb and you may overheat your tool or break it.

Watch out for any blue chips when cutting steel.....You are probably going too fast! If the saw teeth themselves are blue, it is probably too late....Go out and buy another saw. hmm

Coolant will help keep the saw and work cool and reduce the tendency of the chips to weld themselves together and to the tool.

For me slow is better.

Regards
John

Edited By John McNamara on 16/05/2014 09:33:48

Tt the end of the first page of this  thread is my take on trepanning. Although I have done it a few times now it still causes a fierce clenching of the buttocks when approaching the end of the operation.

How do I post a link properly?

Copy the url as you did then when typing your message, highlight a suitable word such as "this" then click on the icon of a world globe with chain Link, a window will open where you can paste the url

Edited By ANDY CAWLEY on 16/05/2014 09:51:55

Link and explaination added by Jason B

Edited By JasonB on 16/05/2014 10:27:01

Rotabroach cutters are useful for this if a suitable holder is made for them. Though 80mm maybe a little large for them. I should say that I haven't done this but I caught something on youtube and it seemed like a good idea. It is only a matter of time before I stumble across some to try it out.

David

+1

Post deleted. (Andy has now inserted the link.)

Edited By Les Jones 1 on 16/05/2014 10:37:12

Edited By Les Jones 1 on 16/05/2014 10:41:29

A spoon bit drill would probbly work in aluminium.

Spareys "The Amateurs Lathe" mentions them

If you don't have any special tooling, hole saw etc., you can do as I did yesterday. I had a 1.5" hole to bore in a bit of 1/2" steel plate, so I decided to do what I suggested in another resent thread, I drilled it 1" set up in the 4 jaw chuck, then I mounted (in this case, and for no reason other than it was first I came to), a 9/16" drill in the tool post, and set it pointed at the hole, and angled toward me, I then used it as a boring bar, I took it quietly .050" on diameter per cut, I might as well have been using a boring bar, it cut just the same.

A trepaning tool is just a parting type tool used on the face of the work in the chuck. On the side that is on the outside of the cut the tool is ground away to clear the arc of the circle. On your 10 mm aluminium it would be possible to do it in one cut, but better to go half way through then turn it over and go in from the other side, you should be able to get fairly close to diameter, but even just using the trepaning tool you cane bore the final few thou.

Ian S C

If you only have the one to do then drill it with the biggest drill bit you have and open it out using a boring bar. You can probably have it done in less time it takes to read all the replies and get your hands on the necessary equipment.

Steve

I totally agree with Steve, all this faffing around with trepanning & hole saws is very time consuming if you are only talking about small quantities.

Tony

Thanks guys, I will invest in some larger hole saws

Edited By ANDY CAWLEY on 17/05/2014 06:06:36

Hmmm! I just tried to add a photo and that didn't work either.

Edited By ANDY CAWLEY on 17/05/2014 06:06:00