Half-round drills.... uses for?

[J Tiers]

Sorting out some "stuff", I found a packet of 0.091" dia half round drills.

What special use are they for? Similar to gundrills?

Searches on various forums seem to suggest that they act similar to gundrills, but most gundrills are 3/4 round, instead. That would prevent them wandering better than only a half-round solid part.

These are only about 4 thou over half diameter in the solid part. They are 0.049 solid, 0.091 total. Maybe enough, maybe not.

Curious, mostly, no application in mind.

[lynnl]

Half-round holes, of course!

That should be obvious.

[PTSideshow]

Years ago they used half round drills for drilling in glass and hard tile. Before the current carbide drills became affordable. You put a wall of clay or putty around the spot and mixed up some light oil and grit to form a paste used a drill press to put the hole in only did it once that it worked well. I guess that it was a quired touch. Perfer the modern diamond glass drills or the carbide grit drills of today LOL.

Have a number of Delta jig saw blade packets with blades for cutting bone, leather, cardboard or paper. About 6-8 teeth to the inch. weird looking blades.

------------------
Glen
Been there, probally broke it doing that

[This message has been edited by PTSideshow (edited 12-30-2005).]

[mmambro]

They are great for drilling thin stock and brass. I also use them for reaming holes in brass and aluminum.

I have a fractional and numbered set.

Mike

[SGW]

I think you're referring to what the Brits call D-bits. Good for finishing a hole to-size in lieu of a reamer, relatively easy to make from drill rod. Early issues of Model Engineer magazine talk about them a lot. Not particularly good for drilling a "complete" hole...drill undersize first, with a regular drill, then finish off.

[Norman Atkinson]

D Bits? We were here just a short while ago.
Tim Leech, if I am not mistaken.

So let's get back to Malbenbut. Oh, yes!
He did an article about bagpipes- and
D- Bits are the correct tool to drill the long holes.

So let's get back to our Mark of the Welsh Marches. So let's get back to Alistair.
Both were onto D-bits.

Anyone would think that memory training went out with the collapse of Pelmanism.

Write it down before you forget it!

Now, what was my name? Nor****? nor lose the Comm** t- tut, tut. It was Rudy- hard to remember.

Right- Norman.

PS- what a load of pillocks!

[J Tiers]

<font face="Verdana, Arial" size="2">Originally posted by NORMAN ATKINSON:
D Bits? We were here just a short while ago.
Tim Leech, if I am not mistaken.
</font>

Bollocks!

I searched AGAIN (including D bits), and your post from which the above was taken was the only result!

Perhaps I have not the mouth correctly held.
Ach so.

The search is apparently best used when you know what you are searching for already, and know what other words should be included (I could suggest a few, but I digress).

Thanks for not calling me an addlepated git, anyhow. That shows either diplomacy on your part, or perhaps merely poor skills at observation.....

So I take it these thinguses are more for a sort of reaming operation?

The gundrill type will drill from the solid, and seem to be best at that. They do need a starter hole on location and correct size.

The half-round look too fragile for much.

[Norman Atkinson]

JT!

Would I call you - damn, I've forgotten.

Seriously, Tim was prattling on- sorry, matey- about drilling fancy holes.
Me computer has had a Malbenbut- sorry, Malware and I gawn an lorst me records.
At present, I am limping on small hard drive.
When you get to my age, everything goes soft.

I also prattled on about Ian Bradley- and the Drilling Machine and also the Grinding Machine. Both by Tee. They have D Bits and one goes on to doing bits for engraving machines.
Now, JT, might I quote the Gospel of St George Thomas, the Divine?
"For this chapter, a D bit is a tool for producing a parallel hole as nearly as possible true to size, therefore it must not be capable of cutting on its sides"

Obviously, GHT in true tradition expands his advice to- lesser mortals like me.

Oh, and a Happy New Year.

Norm

[phil burman]

<font face="Verdana, Arial" size="2">Originally posted by J Tiers:
Bollocks!

I searched AGAIN (including D bits), and your post from which the above was taken was the only result!

Perhaps I have not the mouth correctly held.
Ach so.

The search is apparently best used when you know what you are searching for already, and know what other words should be included
</font>

Try searching for this thread "D bit Geometry Question"
start by me on the 08.16.2005

Phil

[Norman Atkinson]

Well, thank you Phil!
It finished on the 21st August 2005.

All protagonists- sorry, contributors- mentioned appeared in the plot.

Did I say all that? Yuk!

Nah then, J! You take a chunk of say African Blackwood of 13 inches long and have to drill a 3.5 mm hole all the way through it. Yer might have to do a bit shorter lengths but get a parallel hole of only 3mm. The easy bit is drilling the tone holes in the chanter.

Interesting stuff, I promise.


Cheers

Norm