# Cutting an outer ring.



## barnesrickw (Sep 26, 2015)

I have a project that requires cutting a large outer ring from a piece of round stock.  How do I best go about doing this?  The inside diameter is a little over three inches.  View attachment ImageUploadedByModel Engines1443316021.797991.jpg


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## goldstar31 (Sep 26, 2015)

Glue it on a ply board on a faceplate and use a trepanning tool in the lathe tool holder.

I don't know what other kit that you may have available but that is probably the simplest on a lathe that has minimum accessories.

Norman


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## bazmak (Sep 27, 2015)

I have just done the same thing.In order to save a large chunk of alum 
i drilled and ran a jigsaw thru then machine as required


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## 10K Pete (Sep 27, 2015)

Put it in yer 3 jaw and trepan out the center. Done it a zillion times!

Pete


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## goldstar31 (Sep 27, 2015)

If you know how to grind up a lathe tool- and I would remind readers that it a part of lathe work, a trepanning tool is only a boring tool with clearance on both sides of the tool.

But as for a jigsaw? What about when there is need to cut in a harder metal?


One has to bite the bullet and learn - sometime. Or write here  and re-raise the same old question- time and time again-- and as one of my good friends says- get the same silly answers.

He is a world authority on many aspects of engineering- full size and model- and he is right.

My views too, because a trepanning tool is really akin to a penknife- which is common enough.

'Nuff said


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## kvom (Sep 27, 2015)

If you have a rotary table on your mill that's another option.


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## Brian Rupnow (Sep 27, 2015)

I just did that yesterday. The jaws on my 3 jaw chuck wouldn't open far enough to grip the outer diameter, so I mounted the 4 jaw chuck in my lathe and reversed the jaws.--this gives a much larger diameter capacity, but requires that you use a dial indicator to center the piece in the 4 jaw. Then drill a pilot hole, then go up in 1/4" steps to your largest drill held in the tailstock chuck. Then mount a boring tool in the toolpost and spend an hour boring out to the desired size. If your o.d. was roughed out slightly oversize before you started, then remount the 3 jaw chuck, expand the chuck jaws to grip inside the hole you have just bored, and turn the finished outer diameter. The ring I made was 5.54" o.d. with a 3.54" center hole.---Brian


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## bazmak (Sep 27, 2015)

Goldstar,if it had been harder matl i would not have used a jigsaw
It was alum and it worked. Enough said


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## kvom (Sep 27, 2015)

A 3-jaw can work if the jaws are reversible.


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## tornitore45 (Sep 27, 2015)

Boring out turns a valuable piece of AL into swarf.
Trepanning is simple once you get the principle.

The bit should be similar to a ground parting tool, not much longer than the blank thickness.
Choose the tool face with so that the grinding the clearance radius and the tool bit height leave you with some thickness at the bottom for strength.

The outside edge should be radiused for clearance to the part ID 
The edge facing the axis can be vertical or offer a slight clearance.
When chip evacuation become difficult move a bit toward the center and widen the kerf.

On difficult material or large diameter 6 or more holes can be pre-drilled to be 1/2 way into the kerf path to break the chip without creating an interrupted cut.

Lubricate as you would for parting.


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## Charles Lamont (Sep 27, 2015)

kvom said:


> A 3-jaw can work if the jaws are reversible.



Generally 3-jaw chuck jaws are not reversible, but there should be 2 sets, one 'inside' and one 'outside'.


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## goldstar31 (Sep 27, 2015)

This trepanning thing is not exactly new. The Egyptians were trepanning skulls at the time of pharaohs. 
My orthodontic daughter has just phoned me. She has her Mum's skull in a Jacob's Cream Cracker  box which she  had when she got her Fellowship of the Royal College of Surgeons. Me, well, I started with these things long before all that. There was trepanned skull and a Bronze Age skeleton in the den of a guy who taught me lathe work.

Thinking of that time, the Brits perfected a way into war time magnetic sea mines and bombs  by trepanning-- and it is still on the secret list. 

So no great thing. I was suggesting the way for someone with minimal tooling.

Norman


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## tornitore45 (Sep 27, 2015)

The prehistorical skull trepanation has nothing in common with the mechanical procedure except the word and the basic meaning associated with a making a hole.

All medical use of the term trepanation are effectively equivalent to drilling since the removed material is not saved but lost.

In the machining contest there is a substantial difference between drilling, boring and trepaning, the latter results in producing a hole and a plug.

The origin of the word refers to a tool similar to an auger, to that respect the machining term is somewhat incorrect but more practical than "single point hole sawing".  For what is worth any kind of drill tool is called a Trapano in Italian.


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## bazmak (Sep 27, 2015)

anyone tried a treppanning tool in a boring hd


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## goldstar31 (Sep 27, 2015)

bazmak said:


> anyone tried a treppanning tool in a boring hd


 
It's getting  a wee bit( pun intended) confused but back to the topic- it's a 'Granny's Tooth' in woodworking.

As far as 'boring heads are concerned' there is no reason not to use a trepanning tool- or use an fixed end or slot drill- to do ball handles or anything else. 

Does this auger well for the future?:hDe:


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## tornitore45 (Sep 27, 2015)

I used a boring head in the mill to cut a disk or a hole (depending on what the desired piece is) from thin sheet metal.
Holding a (large) piece of sheet metal in the late is often not practical.
Lacking a mill clamping a piece of sheet metal on top of wood onto a face-plate will achieve the same purpose.


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## goldstar31 (Sep 28, 2015)

tornitore45 said:


> I used a boring head in the mill to cut a disk or a hole (depending on what the desired piece is) from thin sheet metal.
> Holding a (large) piece of sheet metal in the late is often not practical.
> Lacking a mill clamping a piece of sheet metal on top of wood onto a face-plate will achieve the same purpose.


 

Thank you for agreeing with my first posting.


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## Swifty (Sep 28, 2015)

I too have used a boring head to treppan a disk from sheet metal. If treppanning a thicker piece in the lathe, its advisable to use the tool upside down and run the job in reverse if the tool wont reach right across, this helps a lot with chip removal.

Paul


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## barnesrickw (Sep 28, 2015)

Once again it looks like I came to the right place for help.  Thank you all.  I'll start by looking into trepanning.


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## Noitoen (Sep 28, 2015)

The direct translation for the Portuguese word _*broca craneana*_ "hole saw" is skull saw.


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## Blogwitch (Sep 30, 2015)

It is very easy to do using the mill and RT. Watch the first part of this vid to see it being done. No special cutting tools needed.

[ame]https://www.youtube.com/watch?v=P1ifPuImERA[/ame]


John


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## xpylonracer (Sep 30, 2015)

My vote would be with the jigsaw method to cut the circle, then a boring tool with the job held in the 4 jaw. The chap asking the question sounds like he's new to lathe work so suggesting trepanning ups the rate of difficulty, even experienced operator's do experience problems and they know about tool grinding, speeds and feeds.
Emgee


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## RogerP (Sep 30, 2015)

The mill method is probably the best way BUT I don't think that the OP has the equipment. Yet


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