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Core drilling questions phildcrowNOSPAM 10-18-2007
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Posted by Tim Mulvey on October 26, 2007, 7:12 pm

>>
>>
>>
>>
>>
>> >> > the correct sequence is: blow brush blow brush
>> >> > the last thing to go in the hole (before the epoxy) must be the
>> >> > brush.
>> >> > if you blow last, it coats the hole with dust & weakens the epoxy
>> >> > bond
>>
>> >> Interesting, Bob. Simpson's instructions for their SET epoxy say to
>> >> "blow brush blow". Do you think that they have it wrong?
>>
>> >> <http://www.simpsonanchors.com/catalog/adhesives/adhesive_anchoring_in...>
>>
>> >> Cheers, Wayne
>>
>> > My experience plus my interaction with home office Hilti
>> > engineers ....they said brush, blow, brush
>>
>> > They explained that the "final brush" drops the drops the dust off
>> > the hole wall.
>>
>> > I added the extra blow / vacuum on the front end but kept the Hilti
>> > "finish with brush"
>>
>> > Again my experience based on drilling, cleaning, bonding & testing
>> > anchors in concrete in the lab.
>>
>> > flour (dust) is used as a release agent when working with dough
>>
>> > paint doesn't stick to dust; I use a brush & a tack cloth when
>> > prepping for paint
>>
>> > YMMV.....draw your own conclusions
>>
>> > counter argument / theory? :)
>>
>> > cheers
>> > Bob
>>
>> Hilti says brush,blow for their epoxy systems. End it by brushing and the
>> hole won't be clean enough. You don't need to brush at all, only blow if
>> you
>> use the HVA capsules.
>>
>> Tim
>
> That's not what the Hilti factory new adhesive development engineer
> told me in 1997.
>
> brush, blow, brush
>
> has got to leave a more dust free surface than
>
> brush, blow
>
> maybe they did more testing but when I was doing testing for them it
> was
>
> brush, blow, brush
>
> and that's what I've done (& still do) and the anchors test out just
> fine.
>
> cheers
> Bob
>

I hear you Bob. There's usually more than one way to do something and still
end up with a quality product. But, when an architect or engineer specs a
certain product, we're obligated to follow the manufacturers instructions.
That way, provided things are done correctly, it's alot harder for problems
to come back and bite the installer. Sometimes, as in your case, things test
out just fine. However, I've also seen the other side. Mostly with metal
roofing, flashings, etc. where guys either took shortcuts or thought they
knew more than the manufacturers. It's no fun going back to repair or
replace someone elses shoddy work in order to get the warranty reinstated or
stop leaks. I just figure that after spending thousands or millions of
dollars on research and development of a product or a system, the least I
can do is install per their instructions. It can save me alot of pain down
the road.

Have a good one
Tim



Posted by Bobk207 on October 27, 2007, 12:13 am
>
>
>
>
>
>
>
> >> >> > the correct sequence is: blow brush blow brush
> >> >> > the last thing to go in the hole (before the epoxy) must be the
> >> >> > brush.
> >> >> > if you blow last, it coats the hole with dust & weakens the epoxy
> >> >> > bond
>
> >> >> Interesting, Bob. Simpson's instructions for their SET epoxy say to
> >> >> "blow brush blow". Do you think that they have it wrong?
>
> >> >>
<http://www.simpsonanchors.com/catalog/adhesives/adhesive_anchoring_in...>
>
> >> >> Cheers, Wayne
>
> >> > My experience plus my interaction with home office Hilti
> >> > engineers ....they said brush, blow, brush
>
> >> > They explained that the "final brush" drops the drops the dust off
> >> > the hole wall.
>
> >> > I added the extra blow / vacuum on the front end but kept the Hilti
> >> > "finish with brush"
>
> >> > Again my experience based on drilling, cleaning, bonding & testing
> >> > anchors in concrete in the lab.
>
> >> > flour (dust) is used as a release agent when working with dough
>
> >> > paint doesn't stick to dust; I use a brush & a tack cloth when
> >> > prepping for paint
>
> >> > YMMV.....draw your own conclusions
>
> >> > counter argument / theory? :)
>
> >> > cheers
> >> > Bob
>
> >> Hilti says brush,blow for their epoxy systems. End it by brushing and the
> >> hole won't be clean enough. You don't need to brush at all, only blow if
> >> you
> >> use the HVA capsules.
>
> >> Tim
>
> > That's not what the Hilti factory new adhesive development engineer
> > told me in 1997.
>
> > brush, blow, brush
>
> > has got to leave a more dust free surface than
>
> > brush, blow
>
> > maybe they did more testing but when I was doing testing for them it
> > was
>
> > brush, blow, brush
>
> > and that's what I've done (& still do) and the anchors test out just
> > fine.
>
> > cheers
> > Bob
>
> I hear you Bob. There's usually more than one way to do something and still
> end up with a quality product. But, when an architect or engineer specs a
> certain product, we're obligated to follow the manufacturers instructions.
> That way, provided things are done correctly, it's alot harder for problems
> to come back and bite the installer. Sometimes, as in your case, things test
> out just fine. However, I've also seen the other side. Mostly with metal
> roofing, flashings, etc. where guys either took shortcuts or thought they
> knew more than the manufacturers. It's no fun going back to repair or
> replace someone elses shoddy work in order to get the warranty reinstated or
> stop leaks. I just figure that after spending thousands or millions of
> dollars on research and development of a product or a system, the least I
> can do is install per their instructions. It can save me alot of pain down
> the road.
>
> Have a good one
> Tim

Tim-

I am an engineer AND I have done 100's of installed & tested anchors
(pulled to failure) for various mfr's.

The procedure was brush, blow, brush

now it looks like they say in their instructions brush, blow (omitting
the final brush)

looks to me like a short cut...........I'm giving my Hilti contact a
call on Monday to get the straight story.

cheers
Bob


Posted by DanG on October 25, 2007, 10:42 pm
I've sure set a lot of chemical anchors, but not in the thousands
on any one job. Most of my applications have been indoors so we
developed a brush and suck method. A plumber's wire brush, cut
off the handle, chuck it into a battery drill and rig whatever
tube on a good shop vac to go to the bottom of the hole has worked
well for us. As has been said, controlling the depth is critical
if you can't run wild. What on earth are you setting that only
needs a 1/4" exposure and 1/8" tolerance? I think the biggest
issue will be maintaining that type of tolerance. I don't think I
would even consider a core drill, it sounds like a heavy hammer
drill or rotary hammer job to me unless they are so close together
that they generate a fracture line. You might consider two bits
in two drills, a lead hole with a 1/4" bit in a light weight SDS
drill for accuracy followed by the 7/8 in a heavier drill.
Another concern is concrete depth if you are drilling 3 1/2" are
you approaching blowing out the bottom? Relton and others make
special rebar cutting bits that work in the same size hole you are
drilling: http://www.relton.com/

Please follow up with your results.

--
______________________________
Keep the whole world singing . . . .
DanG (remove the sevens)
dgriff237@7cox.net



> Hi all,
>
> I have a question about core drill bits: How long do they last?
> I've
> got literally thousands of holes, 7/8" diameter, 3 1/2" deep to
> drill
> into concrete and epoxy all-thread rods for a job, and none of
> the
> factory reps seem to want to give me a straight answer on how
> many
> holes I can get from one bit. The Hilti guy wouldn't even get
> pegged
> down between 50 and 500. I can assume I'll hit the occasional
> rebar,
> but the plans outline the bolts not being in line with the
> rebar. And
> we all know that if it's in the plans that way, that's exactly
> how it
> was built, right? I know I'll need a bunch of bits (right now
> I'm
> figuring 200 holes per bit), but at a hundred bucks apiece, I
> want to
> estimate enough of them into the job that I won't take a huge
> hit
> buying bits.
>
> I don't want to use a roto-hammer as most of these bolts are 4"
> away
> from the edge of the concrete pedestal, and I'm worried both
> about
> precision (not having the drill straight or having it wander)
> and
> breaking off the edges of the concrete pedestals that I'll be
> drilling
> on. Also, if I hit rebar with the roto-hammer, I'm in a bad
> way,
> because these bolts can't be moved.
>
> Third, how long does it take? How many minutes to core drill a
> hole,
> remove the core, clean out the hole, insert some epoxy and set
> an
> anchor bolt to grade? If my per-hole estimate is wrong by one
> minute,
> that equals about 9 days of production. I realize it's just a
> guess,
> but I want it to be an educated one, and frankly, I'm not very
> educated on the production aspects of 7/8" core drilling.
> Currently,
> the average of people I've surveyed is about 10 minutes.
>
> If any of you have any thoughts or guidance on this issue, I'd
> appreciate your wisdom and opinions.
>
> Thanks,
>
> Phil
>



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