I finally got round to putting up the handrail I mentioned in a post a
week or two ago. The company I bought it from modified their standard
design after I sent them photos where it was to be fitted. It came with
eight M6 x 100mm Thunderbolt concrete screw anchors.

As many others here agree, Bosch multipurpose drill bits are great for
drilling into hard material. I've used them for drilling into concrete
lintels with rebars and they went through pretty easily. For the
handrail posts I needed to drill a 6mm hole at least 100mm deep, so
bought a couple of new drill bits, 6 x 150mm. They had hex shanks, so at
best would do only 120mm, and the flutes didn't extend all the way up.
They are /misdescribed/ he
https://www.screwfix.com/p/bosch-hex-shank-multi-construction-drill-bit-6-x-200mm/490jf.
As the reviews note, they are not 200mm long, but only 150mm. That was
ok for what I needed. The first four holes were in brick. The bits went
through very quickly, and it was easy to screw in the concrete anchors.

But the Bosch bits met their match with the next four holes, which had
to be made in 150mm thick C30 concrete. I could get only one hole 100mm
deep. Two got to 90mm, and the last one only about 75mm. I had been
drilling with an old 550W B&D hammer drill, so thought it best to get
out the 850W SDS Plus drill. This made no difference; the drill bit
remained stubbornly at 75mm depth. When I removed it from the hole I was
amazed. Photo here for comparison with drill bit used once:
https://ibb.co/mS8sfDj
End of blunt drill bit in close-up:
https://ibb.co/8xJs3kk

What in hell can do that to a tungsten carbide tip? I've seen them with
the cutting edge blunted after extended use although the "V" shape is
still there, but /never/ seen one where the carbide bit has been
completely flattened back to the shank.

I bought a small pack of M6 x 75mm concrete screws and put two of those
in with the 100mm one I could get in. For the other one I used a Dremel
with a disc cutter to take it down to 50mm, and I'm sure it didn't go in
properly and has smoothed some of the thread it cut. All were very
difficult to screw in, even using a 300mm Tommy bar. They seem, however,
to have fixed the handrail post pretty well.

Those concrete screws really are hard steel, and it took some effort
with the Dremel to cut one off. However, this is what the cut-off end
looks like after trying to cut a thread in that hard concrete (unused
screw for comparison):
https://ibb.co/KGdkk59
I have my doubts that the smoothed thread grips as well as one might
think. No doubt that some of the screw has all its thread complete near
the top, and that grips better, but are they really suited for use in
very hard concrete with lots of flints and stones?

--

Jeff

On 13/08/2020 11:19, Jeff Layman wrote:
I finally got round to putting up the handrail I mentioned in a post a
week or two ago. The company I bought it from modified their standard
design after I sent them photos where it was to be fitted.Â* It came with
eight M6 x 100mm Thunderbolt concrete screw anchors.

As many others here agree, Bosch multipurpose drill bits are great for
drilling into hard material. I've used them for drilling into concrete
lintels with rebars and they went through pretty easily. For the
handrail posts I needed to drill a 6mm hole at least 100mm deep, so
bought a couple of new drill bits, 6 x 150mm. They had hex shanks, so at
best would do only 120mm, and the flutes didn't extend all the way up.
They are /misdescribed/ he
https://www.screwfix.com/p/bosch-hex-shank-multi-construction-drill-bit-6-x-200mm/490jf.
As the reviews note, they are not 200mm long, but only 150mm. That was
ok for what I needed. The first four holes were in brick. The bits went
through very quickly, and it was easy to screw in the concrete anchors.

But the Bosch bits met their match with the next four holes, which had
to be made in 150mm thick C30 concrete. I could get only one hole 100mm
deep. Two got to 90mm, and the last one only about 75mm. I had been
drilling with an old 550W B&D hammer drill, so thought it best to get
out the 850W SDS Plus drill. This made no difference; the drill bit
remained stubbornly at 75mm depth. When I removed it from the hole I was
amazed. Photo here for comparison with drill bit used once:
https://ibb.co/mS8sfDj
End of blunt drill bit in close-up:
https://ibb.co/8xJs3kk

What in hell can do that to a tungsten carbide tip? I've seen them with
the cutting edge blunted after extended use although the "V" shape is
still there, but /never/ seen one where the carbide bit has been
completely flattened back to the shank.

My guess would be heat. As you dump energy into a small and relatively
well insulated volume of material the temperature will rise. I've not
infrequently "unbrazed" the tungsten carbide inserts from masonry drills
by being over-enthusiastic. Even with Bosch drills you do need to clear
them of debris and take them out to cool with deep holes. It's OK to dip
a hot drill into water (the steam layer prevents it from quenching too
fast). You can also squirt water down the hole using a garden sprayer on
"water pistol" setting.


I bought a small pack of M6 x 75mm concrete screws and put two of those
in with the 100mm one I could get in. For the other one I used a Dremel
with a disc cutter to take it down to 50mm, and I'm sure it didn't go in
properly and has smoothed some of the thread it cut. All were very
difficult to screw in, even using a 300mm Tommy bar. They seem, however,
to have fixed the handrail post pretty well.

Those concrete screws really are hard steel, and it took some effort
with the Dremel to cut one off. However, this is what the cut-off end
looks like after trying to cut a thread in that hard concrete (unused
screw for comparison):
https://ibb.co/KGdkk59
I have my doubts that the smoothed thread grips as well as one might
think. No doubt that some of the screw has all its thread complete near
the top, and that grips better, but are they really suited for use in
very hard concrete with lots of flints and stones?

The important thing with concrete screws is to have a suitable sized
pilot hole in hard concrete. I don't like them much, I much prefer the
Multi Monti type (IIRC SF do an "own brand" version). With these it is
also really important to pilot drill to the shank diameter, then they go
in relatively easily and can be removed and replaced if necessary.

On 13/08/2020 11:19, Jeff Layman wrote:
I finally got round to putting up the handrail I mentioned in a post a
week or two ago. The company I bought it from modified their standard
design after I sent them photos where it was to be fitted.Â* It came with
eight M6 x 100mm Thunderbolt concrete screw anchors.

As many others here agree, Bosch multipurpose drill bits are great for
drilling into hard material. I've used them for drilling into concrete
lintels with rebars and they went through pretty easily. For the
handrail posts I needed to drill a 6mm hole at least 100mm deep, so
bought a couple of new drill bits, 6 x 150mm. They had hex shanks, so at
best would do only 120mm, and the flutes didn't extend all the way up.
They are /misdescribed/ he
https://www.screwfix.com/p/bosch-hex-shank-multi-construction-drill-bit-6-x-200mm/490jf.
As the reviews note, they are not 200mm long, but only 150mm. That was
ok for what I needed. The first four holes were in brick. The bits went
through very quickly, and it was easy to screw in the concrete anchors.

But the Bosch bits met their match with the next four holes, which had
to be made in 150mm thick C30 concrete. I could get only one hole 100mm
deep. Two got to 90mm, and the last one only about 75mm. I had been
drilling with an old 550W B&D hammer drill, so thought it best to get
out the 850W SDS Plus drill. This made no difference; the drill bit
remained stubbornly at 75mm depth. When I removed it from the hole I was
amazed. Photo here for comparison with drill bit used once:
https://ibb.co/mS8sfDj
End of blunt drill bit in close-up:
https://ibb.co/8xJs3kk

What in hell can do that to a tungsten carbide tip? I've seen them with
the cutting edge blunted after extended use although the "V" shape is
still there, but /never/ seen one where the carbide bit has been
completely flattened back to the shank.

I bought a small pack of M6 x 75mm concrete screws and put two of those
in with the 100mm one I could get in. For the other one I used a Dremel
with a disc cutter to take it down to 50mm, and I'm sure it didn't go in
properly and has smoothed some of the thread it cut. All were very
difficult to screw in, even using a 300mm Tommy bar. They seem, however,
to have fixed the handrail post pretty well.

Those concrete screws really are hard steel, and it took some effort
with the Dremel to cut one off. However, this is what the cut-off end
looks like after trying to cut a thread in that hard concrete (unused
screw for comparison):
https://ibb.co/KGdkk59
I have my doubts that the smoothed thread grips as well as one might
think. No doubt that some of the screw has all its thread complete near
the top, and that grips better, but are they really suited for use in
very hard concrete with lots of flints and stones?



the TC tip is typically welded onto the drill. if the drill tip gets too
hot, the weld melts and so does the drill bit and shank.

This is quite common when drilling hard tiles. I have had occasions
where I pulled out the drill bit when progress slowed down only to find
the tip was glowing orange-red!

Basically use a new drill bit. drill for short periods of time, withdraw
drill bit use something like compressed air to cool it down and drill again

Also consider the drill speed and the amount of force you are applying
to the drill tip.

S.

In article ,
Jeff Layman wrote:
I finally got round to putting up the handrail I mentioned in a post a
week or two ago. The company I bought it from modified their standard
design after I sent them photos where it was to be fitted. It came with
eight M6 x 100mm Thunderbolt concrete screw anchors.

As many others here agree, Bosch multipurpose drill bits are great for
drilling into hard material. I've used them for drilling into concrete
lintels with rebars and they went through pretty easily. For the
handrail posts I needed to drill a 6mm hole at least 100mm deep, so
bought a couple of new drill bits, 6 x 150mm. They had hex shanks, so at
best would do only 120mm, and the flutes didn't extend all the way up.
They are /misdescribed/ he
https://www.screwfix.com/p/bosch-hex-shank-multi-construction-drill-bit-6-x-200mm/490jf.
As the reviews note, they are not 200mm long, but only 150mm. That was
ok for what I needed. The first four holes were in brick. The bits went
through very quickly, and it was easy to screw in the concrete anchors.

But the Bosch bits met their match with the next four holes, which had
to be made in 150mm thick C30 concrete. I could get only one hole 100mm
deep. Two got to 90mm, and the last one only about 75mm. I had been
drilling with an old 550W B&D hammer drill, so thought it best to get
out the 850W SDS Plus drill. This made no difference; the drill bit
remained stubbornly at 75mm depth. When I removed it from the hole I was
amazed. Photo here for comparison with drill bit used once:
https://ibb.co/mS8sfDj
End of blunt drill bit in close-up:
https://ibb.co/8xJs3kk

What in hell can do that to a tungsten carbide tip? I've seen them with
the cutting edge blunted after extended use although the "V" shape is
still there, but /never/ seen one where the carbide bit has been
completely flattened back to the shank.

Have you met a steel reinforcing rod/bar? Or does the concrete mix have
flints in it?

--
from KT24 in Surrey, England
"I'd rather die of exhaustion than die of boredom" Thomas Carlyle

On 13/08/2020 11:19, Jeff Layman wrote:

But the Bosch bits met their match with the next four holes, which had
to be made in 150mm thick C30 concrete. I could get only one hole 100mm
deep. Two got to 90mm, and the last one only about 75mm. I had been
drilling with an old 550W B&D hammer drill, so thought it best to get
out the 850W SDS Plus drill. This made no difference; the drill bit


The SDS used with normal bits, won't have that much advantage really
(although the typical SDS rotation speed might be a better match). SDS
with a SDS bit however should be a world of difference.

remained stubbornly at 75mm depth. When I removed it from the hole I was
amazed. Photo here for comparison with drill bit used once:
https://ibb.co/mS8sfDj
End of blunt drill bit in close-up:
https://ibb.co/8xJs3kk

What in hell can do that to a tungsten carbide tip? I've seen them with
the cutting edge blunted after extended use although the "V" shape is
still there, but /never/ seen one where the carbide bit has been
completely flattened back to the shank.

Yup, that does look shagged (to use the technical term!)

Looks like it was overheated... Combination of high rotation speed and
not making fast enough cutting progress probably.

Lower speeds, more drill pressure (for hard stuff you may want 25kg of
weight on the bit), and make sure you clear the dust by withdrawing from
the hole frequently. Even a spray of water into the hole from time to time.


I bought a small pack of M6 x 75mm concrete screws and put two of those
in with the 100mm one I could get in. For the other one I used a Dremel
with a disc cutter to take it down to 50mm, and I'm sure it didn't go in
properly and has smoothed some of the thread it cut. All were very
difficult to screw in, even using a 300mm Tommy bar. They seem, however,
to have fixed the handrail post pretty well.

Those concrete screws really are hard steel, and it took some effort
with the Dremel to cut one off. However, this is what the cut-off end
looks like after trying to cut a thread in that hard concrete (unused
screw for comparison):
https://ibb.co/KGdkk59
I have my doubts that the smoothed thread grips as well as one might
think. No doubt that some of the screw has all its thread complete near
the top, and that grips better, but are they really suited for use in
very hard concrete with lots of flints and stones?

Judging by the insertion torque you used, I am guessing they will be
well stuck in there!


--
Cheers,

John.

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

On 13/08/2020 11:19, Jeff Layman wrote:
I finally got round to putting up the handrail I mentioned in a post a
week or two ago. The company I bought it from modified their standard
design after I sent them photos where it was to be fitted. It came with
eight M6 x 100mm Thunderbolt concrete screw anchors.

As many others here agree, Bosch multipurpose drill bits are great for
drilling into hard material. I've used them for drilling into concrete
lintels with rebars and they went through pretty easily. For the
handrail posts I needed to drill a 6mm hole at least 100mm deep, so
bought a couple of new drill bits, 6 x 150mm. They had hex shanks, so at
best would do only 120mm, and the flutes didn't extend all the way up.
They are /misdescribed/ he
https://www.screwfix.com/p/bosch-hex-shank-multi-construction-drill-bit-6-x-200mm/490jf.
As the reviews note, they are not 200mm long, but only 150mm. That was
ok for what I needed. The first four holes were in brick. The bits went
through very quickly, and it was easy to screw in the concrete anchors.

But the Bosch bits met their match with the next four holes, which had
to be made in 150mm thick C30 concrete. I could get only one hole 100mm
deep. Two got to 90mm, and the last one only about 75mm. I had been
drilling with an old 550W B&D hammer drill, so thought it best to get
out the 850W SDS Plus drill. This made no difference; the drill bit
remained stubbornly at 75mm depth. When I removed it from the hole I was
amazed. Photo here for comparison with drill bit used once:
https://ibb.co/mS8sfDj
End of blunt drill bit in close-up:
https://ibb.co/8xJs3kk

What in hell can do that to a tungsten carbide tip? I've seen them with
the cutting edge blunted after extended use although the "V" shape is
still there, but /never/ seen one where the carbide bit has been
completely flattened back to the shank.

I bought a small pack of M6 x 75mm concrete screws and put two of those
in with the 100mm one I could get in. For the other one I used a Dremel
with a disc cutter to take it down to 50mm, and I'm sure it didn't go in
properly and has smoothed some of the thread it cut. All were very
difficult to screw in, even using a 300mm Tommy bar. They seem, however,
to have fixed the handrail post pretty well.

Those concrete screws really are hard steel, and it took some effort
with the Dremel to cut one off. However, this is what the cut-off end
looks like after trying to cut a thread in that hard concrete (unused
screw for comparison):
https://ibb.co/KGdkk59
I have my doubts that the smoothed thread grips as well as one might
think. No doubt that some of the screw has all its thread complete near
the top, and that grips better, but are they really suited for use in
very hard concrete with lots of flints and stones?

Thanks for all the replies.

When drilling the holes I regularly cleared them of dust using a plastic
tube from a window spray pushed down the hole with blowing at the same
time (goggles definitely required!). So it was never allowed built up.
It was also noted in the anchor information that the hole must be clear
of dust when screwing in.

Although the drill bit got very hot, would it have mattered? Tungsten
Carbide retains its hardness even at red heat. Looking at the close-up
of the tip, you can see the remaining TC at the 2 and 8 o'clock
positions, so it doesn't look like the weld melted and the TC bit fell
out. Newshound mentioned water. Out of interest, what would happen if
water was used as a cooler/lubricant for drilling holes in concrete? It
wouldn't last long, needing constant replacement, but would it have any
useful effect? I wondered if by adding water it might form a "grinding
paste" with the retained concrete dust which might clog the flutes.

The 6mm drill size used was that recommended for the supplied screws. I
wondered if a 6.5 mm drill would have made the thread-cutting and
insertion a tad easier, but maybe it would have been a bit too big.

If I ever need to hold something to concrete again, I'll probably return
to a standard rawlbolt or shield anchor fixing, and certainly not do the
work when it is 30+deg C! :-)

--

Jeff

On Thursday, 13 August 2020 at 15:24:45 UTC+1, Jeff Layman wrote:
On 13/08/2020 11:19, Jeff Layman wrote:
I finally got round to putting up the handrail I mentioned in a post a
week or two ago. The company I bought it from modified their standard
design after I sent them photos where it was to be fitted. It came with
eight M6 x 100mm Thunderbolt concrete screw anchors.

As many others here agree, Bosch multipurpose drill bits are great for
drilling into hard material. I've used them for drilling into concrete
lintels with rebars and they went through pretty easily. For the
handrail posts I needed to drill a 6mm hole at least 100mm deep, so
bought a couple of new drill bits, 6 x 150mm. They had hex shanks, so at
best would do only 120mm, and the flutes didn't extend all the way up.
They are /misdescribed/ he
https://www.screwfix.com/p/bosch-hex-shank-multi-construction-drill-bit-6-x-200mm/490jf.
As the reviews note, they are not 200mm long, but only 150mm. That was
ok for what I needed. The first four holes were in brick. The bits went
through very quickly, and it was easy to screw in the concrete anchors.

But the Bosch bits met their match with the next four holes, which had
to be made in 150mm thick C30 concrete. I could get only one hole 100mm
deep. Two got to 90mm, and the last one only about 75mm. I had been
drilling with an old 550W B&D hammer drill, so thought it best to get
out the 850W SDS Plus drill. This made no difference; the drill bit
remained stubbornly at 75mm depth. When I removed it from the hole I was
amazed. Photo here for comparison with drill bit used once:
https://ibb.co/mS8sfDj
End of blunt drill bit in close-up:
https://ibb.co/8xJs3kk

What in hell can do that to a tungsten carbide tip? I've seen them with
the cutting edge blunted after extended use although the "V" shape is
still there, but /never/ seen one where the carbide bit has been
completely flattened back to the shank.

I bought a small pack of M6 x 75mm concrete screws and put two of those
in with the 100mm one I could get in. For the other one I used a Dremel
with a disc cutter to take it down to 50mm, and I'm sure it didn't go in
properly and has smoothed some of the thread it cut. All were very
difficult to screw in, even using a 300mm Tommy bar. They seem, however,
to have fixed the handrail post pretty well.

Those concrete screws really are hard steel, and it took some effort
with the Dremel to cut one off. However, this is what the cut-off end
looks like after trying to cut a thread in that hard concrete (unused
screw for comparison):
https://ibb.co/KGdkk59
I have my doubts that the smoothed thread grips as well as one might
think. No doubt that some of the screw has all its thread complete near
the top, and that grips better, but are they really suited for use in
very hard concrete with lots of flints and stones?
Thanks for all the replies.

When drilling the holes I regularly cleared them of dust using a plastic
tube from a window spray pushed down the hole with blowing at the same
time (goggles definitely required!). So it was never allowed built up.
It was also noted in the anchor information that the hole must be clear
of dust when screwing in.

Although the drill bit got very hot, would it have mattered? Tungsten
Carbide retains its hardness even at red heat. Looking at the close-up
of the tip, you can see the remaining TC at the 2 and 8 o'clock
positions, so it doesn't look like the weld melted and the TC bit fell
out. Newshound mentioned water. Out of interest, what would happen if
water was used as a cooler/lubricant for drilling holes in concrete? It
wouldn't last long, needing constant replacement, but would it have any
useful effect? I wondered if by adding water it might form a "grinding
paste" with the retained concrete dust which might clog the flutes.

The 6mm drill size used was that recommended for the supplied screws. I
wondered if a 6.5 mm drill would have made the thread-cutting and
insertion a tad easier, but maybe it would have been a bit too big.

If I ever need to hold something to concrete again, I'll probably return
to a standard rawlbolt or shield anchor fixing, and certainly not do the
work when it is 30+deg C! :-)

Maybe there's a diamond at the bottom of your hole!

More seriously, TC is vulnerable to wearing away fast from inadequate hammering, and SDSes can certainly be operated such that the bit does more scraping than hammering.


NT

On 13/08/2020 11:19, Jeff Layman wrote:

snip

Very interesting post, with pics!

Bill

On 13/08/2020 11:19, Jeff Layman wrote:

snip

A real slow speed and efficient SDS hammer action would have helped.
Don't press on. Let the drill do the work.

Bill

On 13/08/2020 15:24, Jeff Layman wrote:
On 13/08/2020 11:19, Jeff Layman wrote:

Thanks for all the replies.

When drilling the holes I regularly cleared them of dust using a plastic
tube from a window spray pushed down the hole with blowing at the same
time (goggles definitely required!). So it was never allowed built up.
It was also noted in the anchor information that the hole must be clear
of dust when screwing in.

Although the drill bit got very hot, would it have mattered? Tungsten
Carbide retains its hardness even at red heat. Looking at the close-up
of the tip, you can see the remaining TC at the 2 and 8 o'clock
positions, so it doesn't look like the weld melted and the TC bit fell
out.

You might still have some tungsten carbide there, but you have still
lost a lot of material from the drill. Where do you think it has gone? I
think you have gone beyond red heat locally. One possibility perhaps is
that having flattened the end of the drill, you then met a piece of
rebar. The Bosch drills are good, but they still rely on the classic
"cutting" geometry to get through steel. (Look up Count Rumford and
canon boring machines).

Newshound mentioned water. Out of interest, what would happen if
water was used as a cooler/lubricant for drilling holes in concrete? It
wouldn't last long, needing constant replacement, but would it have any
useful effect? I wondered if by adding water it might form a "grinding
paste" with the retained concrete dust which might clog the flutes.

Clogged flutes can be a problem with water but a hot drill will mean
they dry out quickly. A wire brush will clear them out.

If you ever get to see substantial industrial diamond disks being used
to cut through metres of concrete, you'll see they are normally flooded
with water.


The 6mm drill size used was that recommended for the supplied screws. I
wondered if a 6.5 mm drill would have made the thread-cutting and
insertion a tad easier, but maybe it would have been a bit too big.

That's definitely a risk with that type of concrete screw; but it sounds
like you have stronger than average concrete.


If I ever need to hold something to concrete again, I'll probably return
to a standard rawlbolt or shield anchor fixing, and certainly not do the
work when it is 30+deg C! :-)

Jeff Layman wrote:

Although the drill bit got very hot, would it have mattered? Tungsten
Carbide retains its hardness even at red heat.

Yes, but as somoene else pointed out the TC tip can become detached
from the rest of the bit if it gets very hot. I think most of my SDS
bit failures have been due to the TC bits at the end 'falling off'/

--
Chris Green
·

On 13/08/2020 18:16, williamwright wrote:
On 13/08/2020 11:19, Jeff Layman wrote:

snip

Very interesting post, with pics!

Pleased you enjoyed it.

I think the score is now only 655 : 1 in your favour. I'm catching up!

--

Jeff

On 13/08/2020 18:12, Nick Cat wrote:

Maybe there's a diamond at the bottom of your hole!

That thought did cross my mind! :-)

More seriously, TC is vulnerable to wearing away fast from inadequate hammering, and SDSes can certainly be operated such that the bit does more scraping than hammering.

See Bill's second reply. It may be that drilling hard masonry is more an
art than a science!

--

Jeff

On 13/08/2020 19:10, newshound wrote:
On 13/08/2020 15:24, Jeff Layman wrote:

You might still have some tungsten carbide there, but you have still
lost a lot of material from the drill. Where do you think it has gone?

I can only assume that if it hadn't disintegrated completely and been
ejected with the concrete dust via the flutes, it was left as a small
lump at the bottom of the hole. That would, of course, probably stop any
further drilling even with a new bit.

Newshound mentioned water. Out of interest, what would happen if
water was used as a cooler/lubricant for drilling holes in concrete? It
wouldn't last long, needing constant replacement, but would it have any
useful effect? I wondered if by adding water it might form a "grinding
paste" with the retained concrete dust which might clog the flutes.

Clogged flutes can be a problem with water but a hot drill will mean
they dry out quickly. A wire brush will clear them out.

I was thinking more about clogging "in situ" which might mean more
"grinding paste" remaining at the drill tip and damaging it.

If you ever get to see substantial industrial diamond disks being used
to cut through metres of concrete, you'll see they are normally flooded
with water.

Good point.

The 6mm drill size used was that recommended for the supplied screws. I
wondered if a 6.5 mm drill would have made the thread-cutting and
insertion a tad easier, but maybe it would have been a bit too big.

That's definitely a risk with that type of concrete screw; but it sounds
like you have stronger than average concrete.

--

Jeff

On Thu, 13 Aug 2020 10:12:14 -0700 (PDT), Nick Cat wrote:

More seriously, TC is vulnerable to wearing away fast from inadequate
hammering, and SDSes can certainly be operated such that the bit does
more scraping than hammering.

And isn't the Bosch drill a "normal" type one not an SDS one? An SDS
whacks the drill far harder than the vibration plate in a "hammer"
drill.

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.

--
Cheers
Dave.

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.

On 13/08/2020 20:17, Dave Liquorice wrote:
On Thu, 13 Aug 2020 10:12:14 -0700 (PDT), Nick Cat wrote:

More seriously, TC is vulnerable to wearing away fast from inadequate
hammering, and SDSes can certainly be operated such that the bit does
more scraping than hammering.

And isn't the Bosch drill a "normal" type one not an SDS one? An SDS
whacks the drill far harder than the vibration plate in a "hammer"
drill.

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.

I used an ordinary B&D hammer drill before using an Energer SDS Plus
drill. That drill comes with an "ordinary" chuck as well as an SDS one,
except that the ordinary chuck has the same SDS Plus shaft as the SDS
chuck has. So I assume it is designed to take ordinary drill bits to use
in SDS hammer mode. I think I would have noticed if the drill bit was
blunt before using it with the SDS drill, as I had to remove it from the
B&D chuck first.

--

Jeff

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.

--

Jeff

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.

Bill

On 13/08/2020 21:22, Jeff Layman wrote:

I used an ordinary B&D hammer drill before using an Energer SDS Plus
drill. That drill comes with an "ordinary" chuck as well as an SDS one,
except that the ordinary chuck has the same SDS Plus shaft as the SDS
chuck has. So I assume it is designed to take ordinary drill bits to use
in SDS hammer mode. I think I would have noticed if the drill bit was
blunt before using it with the SDS drill, as I had to remove it from the
B&D chuck first.


The ordinary chuck is so you can use wood bits, hole saws, etc, with the
hammer turned off. It won't work for hammer action.

Bill

On 13/08/2020 19:50, Jeff Layman wrote:
On 13/08/2020 18:16, williamwright wrote:
On 13/08/2020 11:19, Jeff Layman wrote:

snip

Very interesting post, with pics!

Pleased you enjoyed it.

I think the score is now only 655 : 1 in your favour. I'm catching up!

Ha!

Bill

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.

--

Jeff

On 13/08/2020 21:22, Jeff Layman wrote:
On 13/08/2020 20:17, Dave Liquorice wrote:
On Thu, 13 Aug 2020 10:12:14 -0700 (PDT), Nick Cat wrote:

More seriously, TC is vulnerable to wearing away fast from inadequate
hammering, and SDSes can certainly be operated such that the bit does
more scraping than hammering.

And isn't the Bosch drill a "normal" type one not an SDS one? An SDS
whacks the drill far harder than the vibration plate in a "hammer"
drill.

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.

I used an ordinary B&D hammer drill before using an Energer SDS Plus
drill. That drill comes with an "ordinary" chuck as well as an SDS one,
except that the ordinary chuck has the same SDS Plus shaft as the SDS
chuck has. So I assume it is designed to take ordinary drill bits to use
in SDS hammer mode.

Not usually - in fact quite often the flutes on the add on chucks are
designed such that the chuck will not hammer at all - even if the drill
is set to hammer mode.




--
Cheers,

John.

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

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).

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!


--
Cheers,

John.

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

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 if mass alone would account for it. For example I have some 1m
long SDS bits, and they are a good deal heavier than an add on chuck,
but they drill ok.

--
Cheers,

John.

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

On Friday, 14 August 2020 at 12:22:11 UTC+1, 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.

Bill

The one time I watched it done the chuck shattered on the first hit.


NT

In article ,
Jeff Layman wrote:
On 13/08/2020 20:17, Dave Liquorice wrote:
On Thu, 13 Aug 2020 10:12:14 -0700 (PDT), Nick Cat wrote:

More seriously, TC is vulnerable to wearing away fast from inadequate
hammering, and SDSes can certainly be operated such that the bit does
more scraping than hammering.

And isn't the Bosch drill a "normal" type one not an SDS one? An SDS
whacks the drill far harder than the vibration plate in a "hammer"
drill.

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.

I used an ordinary B&D hammer drill before using an Energer SDS Plus
drill. That drill comes with an "ordinary" chuck as well as an SDS one,
except that the ordinary chuck has the same SDS Plus shaft as the SDS
chuck has. So I assume it is designed to take ordinary drill bits to use
in SDS hammer mode.

I, too, have a standard chuck for my SDS drill. I turn off hammer mode
before using it.

--
from KT24 in Surrey, England
"I'd rather die of exhaustion than die of boredom" Thomas Carlyle

On 14/08/2020 15:35, John Rumm wrote:
On 13/08/2020 21:22, Jeff Layman wrote:
On 13/08/2020 20:17, Dave Liquorice wrote:
On Thu, 13 Aug 2020 10:12:14 -0700 (PDT), Nick Cat wrote:

More seriously, TC is vulnerable to wearing away fast from inadequate
hammering, and SDSes can certainly be operated such that the bit does
more scraping than hammering.

And isn't the Bosch drill a "normal" type one not an SDS one? An SDS
whacks the drill far harder than the vibration plate in a "hammer"
drill.

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.

I used an ordinary B&D hammer drill before using an Energer SDS Plus
drill. That drill comes with an "ordinary" chuck as well as an SDS
one, except that the ordinary chuck has the same SDS Plus shaft as the
SDS chuck has. So I assume it is designed to take ordinary drill bits
to use in SDS hammer mode.

Not usually - in fact quite often the flutes on the add on chucks are
designed such that the chuck will not hammer at all - even if the drill
is set to hammer mode.




+1 Mine's like that.
--
Cheers,
Roger

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).

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!



Indeed. If he's got an SDS drill, why on earth didn't he use an SDS bit?

I was confused about the drill size, too. If using 6mm bolts, the hole
needs to be smaller than 6mm (4.5?) so that the threads will cut into
the concrete. It's also a whole lot easier to screw these things in if
you use an impact driver rather than hand tools.
--
Cheers,
Roger

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?

--

Jeff

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 ...

On 14/08/2020 16:44, Roger Mills 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).

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!



Indeed. If he's got an SDS drill, why on earth didn't he use an SDS bit?

It's a good point, but I've never used the SDS drill for drilling - just
using the pick and chisel points to break up lumps of concrete holding
angle-iron fenceposts in the ground. I've never had any problem drilling
using an ordinary hammer drill; as I mentioned I've used it for drilling
lintels with rebars using the Bosch multipurpose bits (as well as
ordinary TCT-tipped bits for drilling ordinary bricks). As it happens
the SDS drill came with a selection of bits, but the smallest was 8mm.

I was confused about the drill size, too. If using 6mm bolts, the hole
needs to be smaller than 6mm (4.5?) so that the threads will cut into
the concrete. It's also a whole lot easier to screw these things in if
you use an impact driver rather than hand tools.

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).

--

Jeff

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...

--
Cheers
Dave.

I really don't see why you didn't use resin anchors and save on all the fancying about.

Cynic wrote:

I really don't see why you didn't use resin anchors and save on all the fancying about.

resin anchors still need holes drilling ...

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.

--

Jeff

On Sat, 15 Aug 2020 08:25:00 +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...

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?

SDS drills are just a heavier construction, may used tougher steel.

I'm not questioning that SDS drills are more efficient at
drilling/hammering than ordinary hammer drills,

It's not just the drill bit it's the machines action. An ordinary
hammer drill just has a chatter plate that makes the end of the drill
vibrate a bit. A SDS uses a pneumatic action to literally hammer the
end of the drill, like hitting a cold chisel with a lump hammer.

The difference between the two is chalk and cheese. How long did it
take to drill those 100 mm deep holes with your hammer drill? An SDS
in the brick would be just a few seconds, the concrete perhaps 5,
unless it's seriously hard, which the hammer drill would barely
touch.

--
Cheers
Dave.

In article , 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.

Looking at some here, the flutes on SDS are much larger and the drill shaft
is also larger, almost the full width of the tip. Both these would allow
the tip to run cooler. Ordinary masonry drills are only meant to stand up
tye hammer action of a normal power drill.

--
from KT24 in Surrey, England
"I'd rather die of exhaustion than die of boredom" Thomas Carlyle

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!

--

Jeff

On 14/08/2020 21:48, Jeff Layman wrote:
On 14/08/2020 16:44, Roger Mills 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).

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!



Indeed. If he's got an SDS drill, why on earth didn't he use an SDS bit?

It's a good point, but I've never used the SDS drill for drilling - just
using the pick and chisel points to break up lumps of concrete holding
angle-iron fenceposts in the ground. I've never had any problem drilling
using an ordinary hammer drill; as I mentioned I've used it for drilling
lintels with rebars using the Bosch multipurpose bits (as well as
ordinary TCT-tipped bits for drilling ordinary bricks). As it happens
the SDS drill came with a selection of bits, but the smallest was 8mm.

I was confused about the drill size, too. If using 6mm bolts, the hole
needs to be smaller than 6mm (4.5?) so that the threads will cut into
the concrete. It's also a whole lot easier to screw these things in if
you use an impact driver rather than hand tools.

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

--
Cheers,

John.

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