On 14/08/2020 21:07, Jeff Layman wrote:
On 14/08/2020 15:43, John Rumm wrote:
On 14/08/2020 13:36, Jeff Layman wrote:
On 14/08/2020 12:22, williamwright wrote:
On 13/08/2020 20:17, Dave Liquorice wrote:

The OP says he changed drilling machine but not if he used and
kanckered an 6 mm SDS bit or used the same Bosch drill in an ordinary
chuck fitted to the SDS machine. Not that you are suposed to use SDS
in hammer mode with such a chuck fitted.


The mass of the chuck inhibits the percussive action. The bit slips. It
just doesn't work.

Not sure about that.

As far as I could see, the chuck was rotating and I could hear and feel
the hammer action. Out of interest, I weighed the chuck - it was 390g.
Add around 30g for the 6mm bit and it comes to 420g. The biggest SDS bit
I have is 22mm in diameter (200 - 250mm long?); it weighs 340g. I can't
see that the 90g would make enough difference to affect the
percussive/rotating action. Bigger SDS bits (25/30mm x 450mm) would
weigh far in excess of the chuck weight, but they would work.

If its like the add on chuck I have, then the pattern of slots on the
shank stop it seating far enough back in the SDS mechanism for the
hammer to hit it. So in hammer mode, you would still feel the vibration
from the anvil flipping back and fourth in the drill, but it would not
be striking the chuck. (and the sound is different, since there is no
metallic "clack" as the shank is struck).

I'll check tomorrow and compare shank patterns.

Having said that, if yours works different to mine and does hammer with
the chuck in, you may have a second problem, since a normal drill bit is
not designed for = 2 Joules of hammer energy per blow - so you might
just shatter the carbide off the end anyway!

I hadn't considered that. Is the tip of an SDS drill bit of
different/heavier construction than an ordinary masonry bit?

Yup, and the fluting on the shank different at well to clear waste
faster. Some bits are two flute, and some are four. In some respects,
SDS bits are more akin to a rawl tool style design - designed such that
the masonry is pulverised by the high impact energy, and the rotation is
basically there to clear the waste, and move to the next are to be hit.
Its all about the hammer rather than the drilling.


--
Cheers,

John.

/================================================== ===============\
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|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On 15/08/2020 08:25, Jeff Layman wrote:
On 14/08/2020 23:36, Dave Liquorice wrote:
On Fri, 14 Aug 2020 21:07:03 +0100, Jeff Layman wrote:

I hadn't considered that. Is the tip of an SDS drill bit of
different/heavier construction than an ordinary masonry bit?

Yes...

Got a good link for that? I can see the SDS-fitting and often the flutes
are different, but how does the SDS tip differ from an ordinary masonry
bit tip? The Tungsten Carbide would be the same material, and AFAIAA the
geometry is the same. I'm not questioning that SDS drills are more
efficient at drilling/hammering than ordinary hammer drills, but I can't
find anything which says the bit tips are any different.



https://en.wikipedia.org/wiki/Drill_bit_shank#SDS_shank

SDS is all about how the drill is held and nothing about the tips at
all. But you can (it appears) get a better hammer action on an SDS.
So as usual Liqour-ish is wrong..




--
€œThe fundamental cause of the trouble in the modern world today is that
the stupid are cocksure while the intelligent are full of doubt."

- Bertrand Russell

On 15/08/2020 11:09, John Rumm wrote:
On 14/08/2020 21:48, Jeff Layman wrote:

The anchors have an overall diameter of 7.5mm. The solid "shaft" of the
bolt is 6mm in diameter, so the threads cut into the concrete by 0.75mm
on each side. I did see mention on one or two webpages of using an
impact driver, but I don't have one (somewhere I have a manual impact
driver, but I've never used it or have needed it. Perhaps that could
have been used to drive in the anchor bolts).

Its a shame the re-used the name, since a manual impact driver is not
really comparable to a powered one. (being designed to break free tight
fasteners rather than quickly drive screws etc with high torque and low
risk of cam out)

http://wiki.diyfaq.org.uk/index.php/...Disambiguation

I'm not sure I could have used a powered impact driver even if I had
one. The baseplate is 100 x 100mm. Welded asymmetrically to that is the
40 x 40mm post - about 5mm from one edge and 55mm from the other
(central between the other two edges. See close-up at
https://blackbourneiron.co.uk/collections/health-beauty-mobility-disability-medical-mobility-furniture-fixtures-handles-rails/products/wrought-iron-style-exterior-handrail-garden-railing-with-one-bolt-down-post).
I think that two holes would have been accessible for use with the
driver, but not the other two as the body of the driver would have got
in the way. Maybe the driver could be used at an angle with a universal
joint. Is that possible?

--

Jeff

On 15/08/2020 11:13, John Rumm wrote:
On 14/08/2020 21:07, Jeff Layman wrote:

I'll check tomorrow and compare shank patterns.

Having said that, if yours works different to mine and does hammer with
the chuck in, you may have a second problem, since a normal drill bit is
not designed for = 2 Joules of hammer energy per blow - so you might
just shatter the carbide off the end anyway!

I hadn't considered that. Is the tip of an SDS drill bit of
different/heavier construction than an ordinary masonry bit?

Yup, and the fluting on the shank different at well to clear waste
faster. Some bits are two flute, and some are four. In some respects,
SDS bits are more akin to a rawl tool style design - designed such that
the masonry is pulverised by the high impact energy, and the rotation is
basically there to clear the waste, and move to the next are to be hit.
Its all about the hammer rather than the drilling.

Out of interest I just compared some masonry bits with identically sized
SDS bits (8, 10, and 12 mm). The masonry bits were Bosch and unbranded;
the SDS were unbranded. The main difference was the flute shaping. The
Bosch 8 and 10mm masonry bits were about a mm less in diameter than the
equivalents SDS bits, but the unbranded masonry bits had the same
diameter as the SDS bits. Other than that there was no difference. As
far as I could tell, the Tungsten Carbide tips were of identical size in
thickness and depth, so I don't think the SDS bit tips are any stronger
than masonry bit tips.

--

Jeff

On 15/08/2020 12:57, Jeff Layman wrote:
On 15/08/2020 11:09, John Rumm wrote:

Its a shame the re-used the name, since a manual impact driver is
not really comparable to a powered one. (being designed to break
free tight fasteners rather than quickly drive screws etc with high
torque and low risk of cam out)

http://wiki.diyfaq.org.uk/index.php/...Disambiguation

I'm not sure I could have used a powered impact driver even if I had
one. The baseplate is 100 x 100mm. Welded asymmetrically to that is
the 40 x 40mm post - about 5mm from one edge and 55mm from the other
(central between the other two edges. See close-up at
https://blackbourneiron.co.uk/collections/health-beauty-mobility-disability-medical-mobility-furniture-fixtures-handles-rails/products/wrought-iron-style-exterior-handrail-garden-railing-with-one-bolt-down-post).
I think that two holes would have been accessible for use with the
driver, but not the other two as the body of the driver would have
got in the way. Maybe the driver could be used at an angle with a
universal joint. Is that possible?

Depends on the head of the fixing. Hex head for an Allen key, can be
driven at an angle with a ball driver bit. Hex bolt head can be driven a
bit off axis with a socket, and Pozidrive screws can also be driven a
little off axis.

If you need to reduce the angle, then fitting an extension bit to the
drill/driver/ID will usually help get at the fixing a bit "straighter"

(also worth noting that you don't have to drill the holes straight
either - angling them will often help get an easier drive angle for the
fixing, and will also make the fixings harder to pull out since they can
be at a combination of angles that can't be pulled in any single
direction).

--
Cheers,

John.

/================================================== ===============\
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|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

SDS drills in my opinion are much kinder on the drill bits. Using hammer drills the bits do tend to knacker with use. I bought an ELU SDS drill approx.. 20+ years ago and bought 6, 7, & 8mm drills at the time, I still have those original bits which are drilling as good as when they were bought and my last house was a real test of machine, drill bits and man with walls made of over baked engineering bricks.

Richard

On 15/08/2020 14:54, Jeff Layman wrote:
On 15/08/2020 11:13, John Rumm wrote:
On 14/08/2020 21:07, Jeff Layman wrote:

I'll check tomorrow and compare shank patterns.

Having said that, if yours works different to mine and does hammer with
the chuck in, you may have a second problem, since a normal drill
bit is
not designed for = 2 Joules of hammer energy per blow - so you might
just shatter the carbide off the end anyway!

I hadn't considered that. Is the tip of an SDS drill bit of
different/heavier construction than an ordinary masonry bit?

Yup, and the fluting on the shank different at well to clear waste
faster. Some bits are two flute, and some are four. In some respects,
SDS bits are more akin to a rawl tool style design - designed such that
the masonry is pulverised by the high impact energy, and the rotation is
basically there to clear the waste, and move to the next are to be hit.
Its all about the hammer rather than the drilling.

Out of interest I just compared some masonry bits with identically sized
SDS bits (8, 10, and 12 mm). The masonry bits were Bosch and unbranded;
the SDS were unbranded. The main difference was the flute shaping. The
Bosch 8 and 10mm masonry bits were about a mm less in diameter than the
equivalents SDS bits, but the unbranded masonry bits had the same
diameter as the SDS bits. Other than that there was no difference. As
far as I could tell, the Tungsten Carbide tips were of identical size in
thickness and depth, so I don't think the SDS bit tips are any stronger
than masonry bit tips.

I did the same earlier, and noted that there were some differences
between the Bosch multi-material and the SDS, although interestingly,
less difference between the SDS and a conventional Masonry bit.

The Bosch have a slightly steeper angle at the tip, and the carbide is
shaped with a flat sharp side on the leading edge. The SDS is bevelled
on both leading and trailing edge. Shank on the SDS was slightly
slimmer, and had a higher twist rate of flues. The Bosch design is
presumably influenced by the need to have a sharp edge to give it the
ability to cut wood / steel as well as masonry. The conventional masonry
bit had a profile similar to the SDS - but obviously its useless in
things other than masonry.

I also had a close look at one of my add on chucks, and noted that does
have the full SDS+ flute pattern, so in theory could be hammered. I
might have to find a masonry bit I don't care about and try and see what
happens!


--
Cheers,

John.

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

On 14/08/2020 21:24, Jim GM4DHJ ... wrote:
On 14/08/2020 07:50, Jeff Layman wrote:
On 13/08/2020 20:36, newshound wrote:
On 13/08/2020 18:16, williamwright wrote:
On 13/08/2020 11:19, Jeff Layman wrote:

snip

Very interesting post, with pics!

Bill

+1. Throws up some interesting problems.

Thanks both for the thumbs up. I guess there have been far too many OT
posts here for some time, and a real DIY query is a tonic for all.
It's what this group /should/ be for.

well slap me ...

Now now, form an orderly queue gents :-)

--
Cheers,

John.

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

On 15/08/2020 11:01, Jeff Layman wrote:
On 14/08/2020 21:07, Jeff Layman wrote:
On 14/08/2020 15:43, John Rumm wrote:

If its like the add on chuck I have, then the pattern of slots on the
shank stop it seating far enough back in the SDS mechanism for the
hammer to hit it. So in hammer mode, you would still feel the vibration
from the anvil flipping back and fourth in the drill, but it would not
be striking the chuck. (and the sound is different, since there is no
metallic "clack" as the shank is struck).

I'll check tomorrow and compare shank patterns.

As you said, it is different.

So I wasn't getting the hammer action I expected. I must invest in a 6mm
SDS drill bit!


Good idea! Be careful to get the length you need. The quoted length
invariably includes the shank, so the the depth of hole you can drill is
a lot (60mm?) shorter.
--
Cheers,
Roger

On 15/08/2020 12:57, Jeff Layman wrote:
On 15/08/2020 11:09, John Rumm wrote:
On 14/08/2020 21:48, Jeff Layman wrote:

The anchors have an overall diameter of 7.5mm. The solid "shaft" of the
bolt is 6mm in diameter, so the threads cut into the concrete by 0.75mm
on each side. I did see mention on one or two webpages of using an
impact driver, but I don't have one (somewhere I have a manual impact
driver, but I've never used it or have needed it. Perhaps that could
have been used to drive in the anchor bolts).

Its a shame the re-used the name, since a manual impact driver is not
really comparable to a powered one. (being designed to break free tight
fasteners rather than quickly drive screws etc with high torque and low
risk of cam out)

http://wiki.diyfaq.org.uk/index.php/...Disambiguation

I'm not sure I could have used a powered impact driver even if I had
one. The baseplate is 100 x 100mm. Welded asymmetrically to that is the
40 x 40mm post - about 5mm from one edge and 55mm from the other
(central between the other two edges. See close-up at
https://blackbourneiron.co.uk/collections/health-beauty-mobility-disability-medical-mobility-furniture-fixtures-handles-rails/products/wrought-iron-style-exterior-handrail-garden-railing-with-one-bolt-down-post).
I think that two holes would have been accessible for use with the
driver, but not the other two as the body of the driver would have got
in the way. MaybeÂ* the driver could be used at an angle with a universal
joint. Is that possible?


No, but you could use an extension bar between impact driver and bit, so
that the bit is at a slight angle to the bolt. That should work,
especially if the bolts use torx bits, which many do.
--
Cheers,
Roger

On 15/08/2020 19:10, John Rumm wrote:
On 15/08/2020 14:54, Jeff Layman wrote:
On 15/08/2020 11:13, John Rumm wrote:
On 14/08/2020 21:07, Jeff Layman wrote:

I'll check tomorrow and compare shank patterns.

Having said that, if yours works different to mine and does hammer with
the chuck in, you may have a second problem, since a normal drill
bit is
not designed for = 2 Joules of hammer energy per blow - so you might
just shatter the carbide off the end anyway!

I hadn't considered that. Is the tip of an SDS drill bit of
different/heavier construction than an ordinary masonry bit?

Yup, and the fluting on the shank different at well to clear waste
faster. Some bits are two flute, and some are four. In some respects,
SDS bits are more akin to a rawl tool style design - designed such that
the masonry is pulverised by the high impact energy, and the rotation is
basically there to clear the waste, and move to the next are to be hit.
Its all about the hammer rather than the drilling.

Out of interest I just compared some masonry bits with identically sized
SDS bits (8, 10, and 12 mm). The masonry bits were Bosch and unbranded;
the SDS were unbranded. The main difference was the flute shaping. The
Bosch 8 and 10mm masonry bits were about a mm less in diameter than the
equivalents SDS bits, but the unbranded masonry bits had the same
diameter as the SDS bits. Other than that there was no difference. As
far as I could tell, the Tungsten Carbide tips were of identical size in
thickness and depth, so I don't think the SDS bit tips are any stronger
than masonry bit tips.

I did the same earlier, and noted that there were some differences
between the Bosch multi-material and the SDS, although interestingly,
less difference between the SDS and a conventional Masonry bit.

Interesting. Unfortunately I don't have a multimaterial bit and SDS bit
of the same size to compare. I guess it's probably because the masonry
bit and SDS bit are essentially for the same purpose.

The Bosch have a slightly steeper angle at the tip, and the carbide is
shaped with a flat sharp side on the leading edge. The SDS is bevelled
on both leading and trailing edge. Shank on the SDS was slightly
slimmer, and had a higher twist rate of flues. The Bosch design is
presumably influenced by the need to have a sharp edge to give it the
ability to cut wood / steel as well as masonry. The conventional masonry
bit had a profile similar to the SDS - but obviously its useless in
things other than masonry.

I assume Bosch spent a lot of R&D time on the cutting edge geometry to
come up with the best compromise for masonry/metal/wood. The ability of
those multimaterial bits to drill through rebar when drilling concrete
is especially useful, as ordinary bits just come to a halt. I've just
found what might be the next step - the SDS quick Multi-Purpose Drill
Bit:
https://www.bosch-diy.com/gb/en/p/sds-quick-multi-purpose-drill-bit-2762960.
Not SDS Plus, though. They have been around for some time, but don't
seem to be available from Screwfix (but are from Amazon). Have you ever
used one of these?

I also had a close look at one of my add on chucks, and noted that does
have the full SDS+ flute pattern, so in theory could be hammered. I
might have to find a masonry bit I don't care about and try and see what
happens!

What else would you be doing on a quiet Sunday in August?!

--

Jeff

On 15/08/2020 19:52, Roger Mills wrote:
On 15/08/2020 12:57, Jeff Layman wrote:
On 15/08/2020 11:09, John Rumm wrote:
On 14/08/2020 21:48, Jeff Layman wrote:

The anchors have an overall diameter of 7.5mm. The solid "shaft" of the
bolt is 6mm in diameter, so the threads cut into the concrete by 0.75mm
on each side. I did see mention on one or two webpages of using an
impact driver, but I don't have one (somewhere I have a manual impact
driver, but I've never used it or have needed it. Perhaps that could
have been used to drive in the anchor bolts).

Its a shame the re-used the name, since a manual impact driver is not
really comparable to a powered one. (being designed to break free tight
fasteners rather than quickly drive screws etc with high torque and low
risk of cam out)

http://wiki.diyfaq.org.uk/index.php/...Disambiguation

I'm not sure I could have used a powered impact driver even if I had
one. The baseplate is 100 x 100mm. Welded asymmetrically to that is the
40 x 40mm post - about 5mm from one edge and 55mm from the other
(central between the other two edges. See close-up at
https://blackbourneiron.co.uk/collections/health-beauty-mobility-disability-medical-mobility-furniture-fixtures-handles-rails/products/wrought-iron-style-exterior-handrail-garden-railing-with-one-bolt-down-post).
I think that two holes would have been accessible for use with the
driver, but not the other two as the body of the driver would have got
in the way. MaybeÂ* the driver could be used at an angle with a universal
joint. Is that possible?


No, but you could use an extension bar between impact driver and bit, so
that the bit is at a slight angle to the bolt. That should work,
especially if the bolts use torx bits, which many do.

The heads of the bolts I had were standard hex. I did have to use
extension bits anyway with the ratchet drive, as its head was too wide
for the bolts at the narrow end.

--

Jeff

On 15/08/2020 19:42, Roger Mills wrote:
On 15/08/2020 11:01, Jeff Layman wrote:
On 14/08/2020 21:07, Jeff Layman wrote:
On 14/08/2020 15:43, John Rumm wrote:

If its like the add on chuck I have, then the pattern of slots on the
shank stop it seating far enough back in the SDS mechanism for the
hammer to hit it. So in hammer mode, you would still feel the vibration
from the anvil flipping back and fourth in the drill, but it would not
be striking the chuck. (and the sound is different, since there is no
metallic "clack" as the shank is struck).

I'll check tomorrow and compare shank patterns.

As you said, it is different.

So I wasn't getting the hammer action I expected. I must invest in a 6mm
SDS drill bit!


Good idea! Be careful to get the length you need. The quoted length
invariably includes the shank, so the the depth of hole you can drill is
a lot (60mm?) shorter.

Yes, I'd found that out (see my first post)! They quote 60mm, although
the flutes go to 75 or 80mm. In practice, provided the hole is
frequently cleared of dust, 100mm is possible, as there is room in the
flutes for the last 20mm of created dust.

As noted in my latest reply to John Rumm, I've just come across SDS
quick multipurpose drill bits. They seem ideal, except I'd need to buy a
new drill!

--

Jeff

On 15/08/2020 20:09, Jeff Layman wrote:
On 15/08/2020 19:10, John Rumm wrote:

I assume Bosch spent a lot of R&D time on the cutting edge geometry to
come up with the best compromise for masonry/metal/wood. The ability of
those multimaterial bits to drill through rebar when drilling concrete
is especially useful, as ordinary bits just come to a halt. I've just
found what might be the next step - the SDS quick Multi-Purpose Drill
Bit:
https://www.bosch-diy.com/gb/en/p/sds-quick-multi-purpose-drill-bit-2762960.
Not SDS Plus, though. They have been around for some time, but don't
seem to be available from Screwfix (but are from Amazon). Have you ever
used one of these?

No not tried those.

I also had a close look at one of my add on chucks, and noted that does
have the full SDS+ flute pattern, so in theory could be hammered. I
might have to find a masonry bit I don't care about and try and see what
happens!

What else would you be doing on a quiet Sunday in August?!

Well I was fixing some metal fence post brackets to the top of the wall,
so needed to get the SDS out, so though while here, I can look at the
bits :^)


--
Cheers,

John.

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

"Jim GM4DHJ ..." Wrote in message:
On 14/08/2020 07:50, Jeff Layman wrote:
On 13/08/2020 20:36, newshound wrote:
On 13/08/2020 18:16, williamwright wrote:
On 13/08/2020 11:19, Jeff Layman wrote:

snip

Very interesting post, with pics!

Bill

+1. Throws up some interesting problems.

Thanks both for the thumbs up. I guess there have been far too many OT
posts here for some time, and a real DIY query is a tonic for all. It's
what this group /should/ be for.

well slap me ...


Do we get to choose what with?
--
Jimk


----Android NewsGroup Reader----
http://usenet.sinaapp.com/

On 14/08/2020 13:36, Jeff Layman wrote:

The mass of the chuck inhibits the percussive action. The bit slips. It
just doesn't work.

Not sure about that.

As far as I could see, the chuck was rotating and I could hear and feel
the hammer action. Out of interest, I weighed the chuck - it was 390g.
Add around 30g for the 6mm bit and it comes to 420g. The biggest SDS bit
I have is 22mm in diameter (200 - 250mm long?); it weighs 340g. I can't
see that the 90g would make enough difference to affect the
percussive/rotating action. Bigger SDS bits (25/30mm x 450mm) would
weigh far in excess of the chuck weight, but they would work.


Have you noticed, though, how the hammer action is less effective with a
heavy bit? I used to have to drill through brick and stone walls very
often, and I found that if the material was hard and the hole was quite
wide it was quicker to drill as far as possible with a short bit, then
change to a longer one when necessary. The reduction in drilling
efficiency when changing from, say a 12mm x 150mm bit to a 12mm x 400mm.

Also, I don't think the way a normal chuck holds the bit doesn't convey
the percussive force very well, presumably due to slipping slightly. You
know how a friction fixing that is seemingly very tight can be adjusted
a fraction of a mm by use of a hammer? A normal chuck is only a friction
fixing, longitudinally.

Bill

On 16/08/2020 20:01, williamwright wrote:
On 14/08/2020 13:36, Jeff Layman wrote:

The mass of the chuck inhibits the percussive action. The bit slips. It
just doesn't work.

Not sure about that.

As far as I could see, the chuck was rotating and I could hear and feel
the hammer action. Out of interest, I weighed the chuck - it was 390g.
Add around 30g for the 6mm bit and it comes to 420g. The biggest SDS bit
I have is 22mm in diameter (200 - 250mm long?); it weighs 340g. I can't
see that the 90g would make enough difference to affect the
percussive/rotating action. Bigger SDS bits (25/30mm x 450mm) would
weigh far in excess of the chuck weight, but they would work.


Have you noticed, though, how the hammer action is less effective with a
heavy bit? I used to have to drill through brick and stone walls very
often, and I found that if the material was hard and the hole was quite
wide it was quicker to drill as far as possible with a short bit, then
change to a longer one when necessary. The reduction in drilling
efficiency when changing from, say a 12mm x 150mm bit to a 12mm x 400mm.

I have no doubt you are right, although I've no experience of short vs
long drill bits. It makes sense in terms of kinetic energy. The short
drill will reach a higher hammer speed as it has less mass to
accelerate, and as kinetic energy is proportional to the square of
velocity, the shorter bit will have more destructive energy than the
longer bit.

Also, I don't think the way a normal chuck holds the bit doesn't convey
the percussive force very well, presumably due to slipping slightly. You
know how a friction fixing that is seemingly very tight can be adjusted
a fraction of a mm by use of a hammer? A normal chuck is only a friction
fixing, longitudinally.

I suppose the rotation would be affected if the bit slipped in the
chuck, but the bit would be touching the end of the chuck where it fits
in the drill body and the hammering would not be any different. Also,
some of the large diameter bits have smaller diameter shanks which fit
in the chuck, and the larger-diameter shoulder rests on the outer end of
the chuck, so again hammering would not be affected.

--

Jeff

jeff Layman wrote:

On 16/08/2020 20:01, williamwright wrote:
On 14/08/2020 13:36, Jeff Layman wrote:

The mass of the chuck inhibits the percussive action. The bit slips. It
just doesn't work.

Not sure about that.

As far as I could see, the chuck was rotating and I could hear and feel
the hammer action. Out of interest, I weighed the chuck - it was 390g.
Add around 30g for the 6mm bit and it comes to 420g. The biggest SDS bit
I have is 22mm in diameter (200 - 250mm long?); it weighs 340g. I can't
see that the 90g would make enough difference to affect the
percussive/rotating action. Bigger SDS bits (25/30mm x 450mm) would
weigh far in excess of the chuck weight, but they would work.


Have you noticed, though, how the hammer action is less effective with a
heavy bit? I used to have to drill through brick and stone walls very
often, and I found that if the material was hard and the hole was quite
wide it was quicker to drill as far as possible with a short bit, then
change to a longer one when necessary. The reduction in drilling
efficiency when changing from, say a 12mm x 150mm bit to a 12mm x 400mm.

I have no doubt you are right, although I've no experience of short vs
long drill bits. It makes sense in terms of kinetic energy. The short
drill will reach a higher hammer speed as it has less mass to
accelerate, and as kinetic energy is proportional to the square of
velocity, the shorter bit will have more destructive energy than the
longer bit.

Also, I don't think the way a normal chuck holds the bit doesn't convey
the percussive force very well, presumably due to slipping slightly. You
know how a friction fixing that is seemingly very tight can be adjusted
a fraction of a mm by use of a hammer? A normal chuck is only a friction
fixing, longitudinally.

I suppose the rotation would be affected if the bit slipped in the
chuck, but the bit would be touching the end of the chuck where it fits
in the drill body and the hammering would not be any different. Also,
some of the large diameter bits have smaller diameter shanks which fit
in the chuck, and the larger-diameter shoulder rests on the outer end of
the chuck, so again hammering would not be affected.

In the absence of any real understanding of the physics involved I am
pretty sure intuitively that the second metal-to-metal junction will
alter the dynamics of the hammer blow and make it much less effective.
You can see this happening when you place something between something
you are hammering and the hammer. I'm sure it's a real effect, though
the maths is totally beyond me. I think sort of bouncing comes into it.



--

Roger Hayter

On Sun, 16 Aug 2020 20:01:00 +0100, williamwright wrote:

Have you noticed, though, how the hammer action is less effective with a
heavy bit?

Is this a normal "hammer" drill or SDS?

Unless the substrate is pretty soft (ordinary brick/block) "hammer"
drills aren't very effective anyway.

With SDS if you don't apply enough pressure the bit just chatters in
the hole, barely making any progress. With enough pressure you get
that satisfying BRRRRUUPPP as the bit "engages" and you might be able
to back the pressure off a little as the bit sinks into the material.
In the former, the mass of the drill absorbs the energy of the
impacts as it rattles up and down the hole. With the latter you have
a Newtons Cradle effect and the impact energy just passes down the
drill with it's mass having very little effect as it's barely moving.

I used to have to drill through brick and stone walls very often, and I
found that if the material was hard and the hole was quite wide it was
quicker to drill as far as possible with a short bit, then change to a
longer one when necessary. The reduction in drilling efficiency when
changing from, say a 12mm x 150mm bit to a 12mm x 400mm.

Can't say I've noticed but then I'd normally start with a shorter and
probably smaller bit to start the hole simply because it's easier to
see the starting position and is easier to control. My long bits are
1000 mm though. B-)

--
Cheers
Dave.