Hi

I entered a competition recently where as the 'element of skill' you had to 
answer three questions, the answers to which were in the product blurb.

One question was 'what depth will the XYZ drill in wood'.  In the blurb it 
was something like 25mm.

However, AIUI that's the maximum diameter capacity, not the depth.  In 
theory a drill will drill any depth hole only subject to the length of the 
drill bit, as long as the maximum diameter isn't exceeded.  So with a 6mm 
bit for example, a hole a metre long is entirely possible?

Have I got that right?

Dave

david lang wrote:


> However, AIUI that's the maximum diameter capacity, not the depth.  In 
> theory a drill will drill any depth hole only subject to the length of the 
> drill bit, as long as the maximum diameter isn't exceeded.  So with a 6mm 
> bit for example, a hole a metre long is entirely possible?


No, you need more oopmph to drill a deeper hole.  As an example, you 
could easily use a 25mm spade bit on a cheapo, underpowered rechargeable 
drill to cut a hole through a sheet of 0.25" plywood, but try using the 
same drill to bore into a solid lump of wood and it will run out of 
steam almost instantly, whereas if your theory above was correct, it 
would keep on drilling until the drill chuck hit the wood surface.

I suppose it's down to friction losses between the side of the drill bit 
and the wall of the hole?

David

Lobster wrote:


> david lang wrote:
> 
>> However, AIUI that's the maximum diameter capacity, not the depth.  In 
>> theory a drill will drill any depth hole only subject to the length of 
>> the drill bit, as long as the maximum diameter isn't exceeded.  So 
>> with a 6mm bit for example, a hole a metre long is entirely possible?
> 
> 
> No, you need more oopmph to drill a deeper hole.  As an example, you 
> could easily use a 25mm spade bit on a cheapo, underpowered rechargeable 
> drill to cut a hole through a sheet of 0.25" plywood, but try using the 
> same drill to bore into a solid lump of wood and it will run out of 
> steam almost instantly, whereas if your theory above was correct, it 
> would keep on drilling until the drill chuck hit the wood surface.


You are sort of both right...

Generally when drill makers state capacity they do mean diameter as per 
the first David's post and not depth. (think about the 1m long SDS bits 
you can buy - I have never seen a maker claim a 1m capacity for masonry 
drilling before!)

There is however an element of friction that comes into play with very 
long bits - so the torque required will climb with the depth of hole as 
you are also having to turn ever more shank in contact with the 
material. You will probably not see this unless the bit is 250mm long or 
more and even then is easy to over come in most materials by pumping the 
drill. This clears debris/swarf from the hole and also widens the 
clearance for the shank a little. IME the drills that have most problem 
in this respect, are long narrow auger bits. I have a 6mm 400mm wood 
auger bit that can bind very tightly in deep holes.

The example of a spade bit was however I feel a poor one, in that these 
are "waisted" bits - i.e. their diameter falls after the spade part of 
the bit. Hence with one of these if you can drill to the depth of the 
spade (inch or two depending on size) then you will be able to carry on 
to any depth after that, since the shank makes no contact with the 
material. (hence why you can get extension bits for spade drills without 
difficulty).



-- 
Cheers,

John.

/=================================================================\
|          Internode Ltd -  http://www.internode.co.uk            |
|-----------------------------------------------------------------|
|        John Rumm - john(at)internode(dot)co(dot)uk              |
\=================================================================/

In an earlier contribution to this discussion,
Lobster   wrote:


> david lang wrote:
>
>> However, AIUI that's the maximum diameter capacity, not the depth.
>> In theory a drill will drill any depth hole only subject to the
>> length of the drill bit, as long as the maximum diameter isn't
>> exceeded.  So with a 6mm bit for example, a hole a metre long is
>> entirely possible?
>
> No, you need more oopmph to drill a deeper hole.  As an example, you
> could easily use a 25mm spade bit on a cheapo, underpowered
> rechargeable drill to cut a hole through a sheet of 0.25" plywood,
> but try using the same drill to bore into a solid lump of wood and it
> will run out of steam almost instantly, whereas if your theory above
> was correct, it would keep on drilling until the drill chuck hit the
> wood surface.
>
> I suppose it's down to friction losses between the side of the drill
> bit and the wall of the hole?
>
> David


It's subject to being able to clear the swarf out of the hole, and to
friction. I guess that a one metre long 6mm bit would be struggling on both
counts!

David's spade bit example only applies to thin material. Once you've drilled
a hole deep enough for the whole cutting end to be inside the wood, the
friction doesn't get any worse as you go deeper.
-- 
Cheers,
Set Square
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On Sat, 10 Sep 2005 13:15:19 GMT, "david lang"
 wrote:

| Hi
| 
| I entered a competition recently where as the 'element of skill' you had to 
| answer three questions, the answers to which were in the product blurb.
| 
| One question was 'what depth will the XYZ drill in wood'.  In the blurb it 
| was something like 25mm.
| 
| However, AIUI that's the maximum diameter capacity, not the depth.  In 
| theory a drill will drill any depth hole only subject to the length of the 
| drill bit, as long as the maximum diameter isn't exceeded.  So with a 6mm 
| bit for example, a hole a metre long is entirely possible?

For the purposes of a competition Yes.   The answer should be as long as
your drill.    I have a specially made. picked up cheap, 6mm masonry drill
which goes through an 11 inch cavity wall just fine.  

-- 
Dave Fawthrop <dave hyphenologist co uk> 
"Intelligent Design?" my knees say *not*.
"Intelligent Design?" my back says *not*.

Set Square wrote:


> Once you've drilled a hole deep enough for the whole cutting end to be
> inside the wood, the friction doesn't get any worse as you go deeper.


But it won't pump out the debris.

This is why augers stick. They need to be in a powerful drill or they
will behave like core samplers.

I find it difficult to believe any firm would advertise a drill only
capable of drilling to a depth of 1" in wood.

In an earlier contribution to this discussion,
Weatherlawyer   wrote:


> Set Square wrote:
>
>> Once you've drilled a hole deep enough for the whole cutting end to
>> be inside the wood, the friction doesn't get any worse as you go
>> deeper.
>
> But it won't pump out the debris.
>
> This is why augers stick. They need to be in a powerful drill or they
> will behave like core samplers.
>

But a spade bit isn't the same as an auger. An auger is the same diameter
over its whole length whereas a spade bit only has a short cutting part on
the end of a long thin shank. You clear the debris by pulling the bit out
while it is still spinning every now and again.
-- 
Cheers,
Set Square
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