[mrogowski]

Morning everyone,

I have a 12" round piece of 1018 that is one inch thick. I need to cut (bore?) out the center 6 inches. Accuracy of cut is not as important to me as safety since I will be machining the two pieces anyway.

Which tool would be more effective/safer to accomplish this on a lathe - a 6" hole saw or a boring tool? I haven't worked on pieces this large and I take safety quite seriously.

Thanks,
Mark

[RICHARD ZASTROW]

Trepanning tool?

[John Welden]

Not sure about a 6 inch hole saw. I guess maybe if your lathe goes slow enough and you have a good way to hold the saw.

Shouldn't be a problem to drill and then bore it out. It will just take a while. I don't see it as being dangerous. The boring bar will be pushing the work into the chuck. Take your time, it's no big deal.

JW

[CalG]

A good jig saw or a band saw through a drilled starter hole would will be very safe.

You say you will machine both pieces, does that imply that you are "saving" the slug?
A 6 inch dia. slug on the loose will never be a sure thing. If you do use the lathe, press that slug into the chuck to keep it from getting away.

If I were going to make a go at this with the lathe, I would work from both sides, and meet half way through the 1 inch depth ;-)

CalG

[ctate2000]

I do not intend to be rude, but the fact that you are asking the question points to a lack of experience. Lack of experience is very dangerous and can hurt you faster than anything else in the shop.

Drill the hole and bore. That is the fastest and safest way.

[HuFlungDung]

If you want to save the core, the method CalG mentioned of trepanning half way through from each side is feasible. In real life, one does not carelessly trepan the slug loose. You can hear a change in pitch as you get near to the cut through point, because the cut starts to sound 'tinny'.

Trepan with a groove that is a bit wider than the toolbit so you can avoid unnecessary jam ups.

When you hear the tinny sound indicating that you are almost through, hit the center with a hammer. If it moves in readily, then you're nearly far enough. You may be able to just hammer it until the thin material breaks away on one side. Or you can drive a narrow cold chisel through the thin material to help break it. Once you've got a crack right through, then typically you can break the slug out just by hammering it around and around.

[Curlychip]

Perhaps face groove leaving about .050 in Z. Then remove from lathe and smack ,beat, or press slug out. A 6" slug loose in a lathe is not pretty.....believe me.

[PixMan]

There are many ways of doing this, but which is best for you depends upon what machine you are using, what type of tooling it takes, how rigid the setup is and how much horsepower it has.

So....whatcha got?

You could start with the biggest drill you have and then make multiple boring passes. That would be the cheapest way out, but not practical if you have many.

I'd use a face groove tool such as a Valenite VG114 R 16 132 40 holder with a VTG 4.0 N 40 GG grade VP5820 insert. One shot, done. Just be prepared to stop the machine just before it breaks through, knock it out by hand, then finish the bore to size with the same tool. If a slug that size breaks through, you'll be buying another new toolholder.

[Superman]

It's only 1" thick

Why not have the supplier oxy-cut, plasma, waterjet it out of plate. He'll probably charge $5 more but do you think you could do it in 5 minutes

[Glacern]

Drill and bore. You probably already have the tools, and you could finish the job in less time than what it would take to buy a hole saw from a local supplier.

[cob]

I do this all the time on a lathe I machine the center out of a pc
theres different ways of doing this the way I always do it. is say I have a 20inch o.d and I want to machine a 10 in hole normally I hold the pcs on a lathe with some 3 hard jaws and put a say 8inch on the tailstock to press it against the hard jaws. then I use a grooving tool to part out the hole in the center. and just like everyone said go about half way then flip the part around and dop the other half way through.
just for safety remember to put the tailstock against the part just so it will not fly out.

[mrogowski]

Thank you all for your suggestions. I guess I should have been more clear in my plans - yes, the intent was to keep the core that I'm cutting out so drilling and boring outward is not an option.

I may end up just taking the piece to someone with a plasma cutter or drill it out manually. And yes, my experience with the lathe is somewhat lacking, hence the reason for posting here.

Best,
Mark