Dampened boring bars for long overhangs

[Neil WyattModerator @neilwyatt]

Posted by Bob Strawson on 26/07/2015 18:20:57:

A drill is far too flexible to use as a boring bar and the outside land would rub.

I can see flexibility could be an issue, but that could be addressed by taking small cuts – a 3/8" drill normally takes two 3/16" deep cuts, so taking 1/32" on one side shouldn't be too much?

I can't see why the land would rub?

This was just a 'get out of jail' thought, I have plenty of proper boring bars but if I even need a deep hole bored perhaps I shall try it and see what happens.

It occurs to me a that a 'single flute' drill  would still have more metal in its cross-section than a d-bit style boring bar and better 'deployed'. It would also have top rake and better chip clearance. At the very least I think there's room for experimenting with better end shapes for solid boring bars than those usually supplied for boring heads.

Neil

Edited By Neil Wyatt on 26/07/2015 20:25:27

[Bob StrawsonParticipant @bobstrawson49673]

The land of a drill, that is, the outside diameter, is ground cylindricaly with no clearance which means it will rub. You can see how flexible a drill is, you can almost bend them by hand but go ahead and try it, nothing lost.

A milling slot drill has side clearance and will work as a boring bar until it becomes disproportionally long compared to its diameter when it too will flex. But any port in a storm! If you don't have a better alternative…….!

Bob Strawson

[Thor 🇳🇴Participant @thor]

Neil,

Like Peter I have made a boring tool from old drills. Since I don't have imperial drills I used a 10mm instead of 3/8". The cutting end has been ground and the drill must be placed at a slight angle to the lathe centerline to give some clearance, so min. hole dia. I can bore is of course larger than the drill dia. As you say, small cuts will work, and the drill can't protrude too far from the holder.

Thor

 

Edited By Thor on 27/07/2015 06:17:34

[Michael GilliganParticipant @michaelgilligan61133]

 

Interesting as these digressions have been … We appear to have strayed from Paul's original topic; and it is worth looking at Sandvik's page about the 'Silent Tools for boring'

The illustration at the top of the page suggests that these tools are on a somewhat larger scale than we are considering!

The video is very impressive; and boring at 6D, to that quality, would be wonderful, but … remember the wise old saying: "you can't scale nature".

MichaelG.

.

P.S. … Some useful explanation, starting on this page … 

Edited By Michael Gilligan on 27/07/2015 08:20:08

[Neil WyattModerator @neilwyatt]

Posted by Thor on 27/07/2015 06:15:22:

Neil,

Like Peter I have made a boring tool from old drills. Since I don't have imperial drills I used a 10mm instead of 3/8". The cutting end has been ground and the drill must be placed at a slight angle to the lathe centerline to give some clearance, so min. hole dia. I can bore is of course larger than the drill dia. As you say, small cuts will work, and the drill can't protrude too far from the holder.

Thor

That's exactly what In had in mind, aside from the useful idea of grinding the end..

If the drill is smaller in diameter than the hole, it won't rub.

Neil

Edited By Neil Wyatt on 27/07/2015 08:29:38

[mickParticipant @mick65121]

A slot drill makes an excellent boring tool, which can easily be off set and remain ridged.

[Clive BarkerParticipant @clivebarker72854]

For boring small holes I have used old taps. Worked well for me.

Clive.

[Peter TuckerParticipant @petertucker86088]

Posted by Neil Wyatt on 26/07/2015 20:18:23:

Yes.

Peter.

Did it work?

It did work, however at the time I did this I wasn't very well set up for tool holding and my system was aukward.

Peter.

[BowberParticipant @bowber]

Posted by Neil Wyatt on 27/07/2015 08:29:02:

That's exactly what In had in mind, aside from the useful idea of grinding the end..

If the drill is smaller in diameter than the hole, it won't rub.

Neil

Edited By Neil Wyatt on 27/07/2015 08:29:38

Of course if the hole is smaller than the drill you could always use it as……… a drill

Steve

[Boiler BriParticipant @boilerbri]

Interesting so what's the smallest boring bar that anyone has used?

Bri

[Nick_GParticipant @nick_g]

Posted by Boiler Bri on 27/07/2015 21:49:11:

 

so what's the smallest boring bar that anyone has used?

Bri

 

Probably the one attached to me and used by my ex girlfriends.

 

Nick

Edited By Nick_G on 27/07/2015 22:06:02

[Ian S CParticipant @iansc]

My smallest one will open out a 3/16"/5 mm hole about 20 mm deep. It was made by grinding up a bit of 1/4"sq HSS tool steel.

Ian S C

[David Clark 13Participant @davidclark13]

I have some that will bore to about 1/8inch upwards. Commercially made they cost about £30 each but I got mine secondhand from the Toolbox in Devon for a couple of £ each.

[mark costello 1Participant @markcostello1]

Nick G, hope that's not the reason She's an ex.

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