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Posted by Bobk207 on October 21, 2007, 1:20 pm
On Oct 21, 9:06 am, phildcrowNOS...@yahoo.com wrote:
> Bob,
>
> My comments are interspersed. Thanks for the insight.
> Phil
>
> > > Phil-
>
> > > You're on the right track ...asking all these questions in advance.
> > > That's the good news.
>
> Thanks.
>
> Snip
>
> > > Having drilling 100's of holes personally, I would suggest a two prong
> > > approach
>
> > > Use the rotary hammer, its faster, cleaner...no water mess. If you
> > > hit rebar stop & finish with the coring system.
>
> > > Is the coring system a Hilti vacuum base? If so make sure you have
> > > the room & appropriate surafce finish for it to suck down.
>
> It is and I do.
>
> Snip
>
> > > Don't lean on the hammer drill, a Hilti hammer drill works fine on its
> > > own weight.
>
> Easier said than done with a crew of carpenters.
>
>
>
> > > I drilled 52 holes 1.125" diameter by 12" deep...used 2 Hiilti hammer
> > > bits, hit partial rebar in 5 holes & cored them no sweat.
>
> > > If your Hilti hammer is variable speed you can easily accurately place
> > > holes. Since your holes are only 3.5" deep I doubt you'll hit much
> > > rebar unless they placed really close to the surface. I'm figuring
> > > its at least 2" deep.
>
> According to the plans, the rebar shouldn't be in the path of the bolt
> holes anyway. And we all know that if it's shown that way on the
> plans, that's how it was built, right?
>
> > > How many men in the drill, prep & place team?
>
> I was thinking two--one to do the actual drilling, one to tend the
> hoses, cords, bits, etc. When the drill guy gets tired, they can
> switch.
>
> > > What chemical anchor are you using?
> > > Who supplies the material? If you supply the material can the hole be
> > > 13/16" (allowable by chem mfr & dwg specs?)
>
> It specs a 7/8" hole. I'm sure the owner would give us a break on it,
> though, if we needed 13/16". We're supplying the epoxy, also called
> out in the plans.
>
> > > mechanical dispenser or pneumatic?
> > > Anchors precut?
> > > Anchor setting tolerance? hole pattern x-y tolerance? protrusion
> > > tolerance?
>
> Electric dispenser, precut anchors, x-y pretty tight (within 1/8" and
> protrusion probably 1/4".
>
>
>
> > > I suggest you "productionize" the process; efficiency is the name of
> > > the game, your crew skill level & motivation are key factors. Simple
> > > aids to production will greatly improve efficiency, work flow
> > > organization is key as well.
>
> We've already discussed templates, layout procedures and order of
> operations. Most of the anchors are in groups of 10 or 12, so we'll
> make a 12-hole template or three, double nut the anchors onto the
> template, drill the holes and set 12 bolts at a time. While the epoxy
> is drying, we'll drill 36 more holes.
>
> > > As you can probably tell, I've done this sort of thing before but
> > > every situation / job site is a little different and for 1000's of
> > > holes, minutes make a huge difference, even 10 seconds per hole
> > > matter. I design & specify these sorts of processes.
>
> > > Your average time estimate is 10 minutes, what was the range in times?
>
> > > Your 10 minute number, at this point, without prior experience or some
> > > process development, is pretty much a WAG (wild ass guess)
>
> While none of the folks I've talked to have drilled holes at a level
> like this, the consensus is 10 minutes to drill the hole, clean it
> out, squirt some epoxy into the hole, and set the bolt.
>
> > > be careful, I'd hate to be very far off on the estimate per hole on
> > > 1000's of holes.
>
> Obviously, while we'd like to be dead-on with our estimate, I'm mostly
> just trying to get into the ballpark with the time estimate. We have
> a schedule we have to meet, and I was wondering how many drilling rigs
> I needed, etc. With our current manpower shortage, I want to have as
> few guys on this as possible, and just have them work for the duration
> of the job on this one item. A few man-days one way or the other
> won't break the bank on this job (it's a big one), but closer to the
> "true" value of the work is always better. That way, there's less
> variability in our estimate, and the smaller contingency we need to
> build in. With less risk, we can bid at a lower margin, and hopefully
> get the job. But I'm sure you knew all that already, Bob. :)
>
> > > cheers
> > > Bob
>
> > Phil-
>
> > All my rambling is all well & good for developing a really good number
> > but if you're not needing to have a really sharp pencil to win the job
> > job it wasn't all that useful.
>
> > Are we talking about a fixed price & you pocket any excess? :)
>
> Yes. This is a lump sum job.
>
> > IMO based on experience, for multiple groups of multiple holes, your
> > 10 minutes per hole is more than adequate. Use that plus 100 holes
> > per bit. Base the bid on all core bits but also use the rotary hammer
> > idea. It'll be faster.
>
> > If you have a decent crew & give them some sort of incentive (& work
> > flow guidance) to work faster I'm sure you can beat that number by a
>
> > BTW a 4" edge distance in decent concrete is plenty for a 7/8" hole.
> > I hammer drilled 1" holes in unreinforced concrete with only 2" edge
> > distance.
>
> That's good to know. Also, I don't think I mentioned it, but this
> concrete is no longer green. It's currently about a month old, so
> it's pretty well set up. If we get the job, we won't get in there for
> at least another month. So that's good.
>
>
>
> > I whimped out on a 2" hole (x 10" deep) with 6" edge distance and used
> > the core drill.
>
> Sissy.
>
> > cheers
> > Bob
>
> Thanks again, Bob, for the insight. I hadn't considered the 2-pronged
> approach. If we can save a few bucks that way, that will be great.
>
> I'll be sure and post an update if we get the job.
>
> Take it easy,
>
> Phil
Phil-
Good luck on getting the job.
Having an electric dispenser will be a big help. On those 52 each 1
1/6" holes by 12" deep we used a dual cartridge hand
dispenser....after about 5 holes we were dying!
I would suggest drilling & "rough" cleaning a large number of holes.
Have a good shop vac with lots of extra filters (washable ones).
Sweep up most of the debris with dust pan & brush.
A modified 2" (or 3") PVC elbow can be used as a vacuum hose nozzle.
Drill a hole thru the back side of the elbow to accept a 1/4" tube on
a modified blow gun.
Using this setup you can blow the holes & capture the debris (so the
crap doens't shoot up into everyone's face)
Sticking with a single process with save a LOT of time, switching
between tasks really eats up time.
SO drilling & rough cleaning is one process (one guy). Drilling is
really quick, clean & easy with a hammer drill. The most tiring
thing will be leaning over the drill. I tend to use the REALLY long
bits, so I can stand at a more comfortable height & controlling
drilling squareness is easier.
If you go with shorter drill bits, encourage the guy to get
comfortable, sit on a bucket or use knee pads
A guy with the vac can follow when the driller gets far enough ahead.
The cleaning process should be:
1) blow with vacuum hose debris catcher
2) brush with proper hole brush
3) blow without vacuum
4) final brush
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
when the "hole cleaner" catches up with the driller, he can switch to
setting anchors.
Depending on whose product you're using & how big the hole diameter
is...the anchors can stand up by themselves.
Be careful on hole depth...too deep & you're screwed.....it makes
controlling anchor protrusion a bitch.
It is easier to shorten a anchor that sticks out too far than deal
with a "shorty". Discuss QC with whoever will check or sign off on
mistakes. I'd m
Whose cutting or supplying the anchors? Are they off-the-shelf Hilti
threaded rod or just cut threaded rod?
Variable anchor lengths will be a problem to deal with.
cheers
Bob
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