Drilling 16mm metal plate...

[skylite]

Hi,

What do you use to drill 16mm metal plates? Normal drill may not work..

What is your comment on the technique of using acetylene torch to put a hole in the metal plates? But it doesn't exactly put a 16mm hole.. but bigger.. so if you use a washer and nut. would it no longer be an effective anchor because of the washer?

The metal plates will not be used for column but for supporting a rafter gable middle (image 2 wide flange welded together and supported by the metal plates)

 

[SlideRuleEra]

What do you use to drill 16mm metal plates?

For field drilling, an industrial rated, 3/4" chuck, geared-down, reversible, single-speed electric drill. One of these will knock you on butt if the bit jams during drilling - plenty of torque.

Here are the specs for this brand:

https://www.milwaukeetool.com/power-tools/corded/1854-1

http://www.SlideRuleEra.net

http://www.VacuumTubeEra.net

 

[racookpe1978]

What diameter hole are you drilling?
That makes a BIG difference in what tool is best.

How accurate is the hole to be located, and to be drilled?

How many holes in a single 16 mm plate?

Is the material magnetic, or an AL or stainless (non-mag) alloy?

What orientation in the plate, is the drill, and the hole?

Are there ANY interferences or restrictions above the plate that might get in the way of the drill?

Are you going to be doing a "one of" or many, or need to go to a whole bunch of different "field" locations?

(Hint: No "good drill" are cheap.

 

[Ron]

A 16mm plate is not a big deal to drill. SRE has given you a photo of the best portable drill you can use for this...and he's right....it will twist your arms off if the bit grabs! Any good quality, high torque drill will do the job for this thickness.

DO NOT USE A TORCH for this! First, you don't need to. Second, the hole will have to be reamed to get a smooth surface. Third, you don't want that much "slop" in the hole size relative to the bolt size, even if you use a washer.

A good, sharp drill bit will go right through the 16mm plate, assuming it is mild steel.

 

[skylite]

The hole is 16mm size for this:

If you use a normal electric drill (SDS) with 16mm drill bit.. can you cut thru the 16mm thick plate (so as not to be confused.. both the thickness of metal plates and hole is 16mm)??

The metal plate is half meter by half meter long.. there will be about 6 holes and only 8 pcs of it.

 

[SlideRuleEra]

If you use a normal electric drill (SDS) with 16mm drill bit.. can you cut thru the 16mm thick plate?

Maybe, maybe not, it depends on the drill and, as Ron stated, the quality of the bit. Try it and see... don't press down too hard, let the drill & bit do the work.

http://www.SlideRuleEra.net

http://www.VacuumTubeEra.net

 

[Brad805]

The only 16mm plate in the detail is the base plate. Why is that not being punched in the shop? If it is indeed the base plate you are drilling you will not be able to get the drill close enough to drill a vertical hole. A 3/4" drive drill as pictured is quite large and has handles one must hold due to the torque when drilling a large hole. They could drill an angled hole, but it your bolts will not fit very well. The first step to drill any hole is to start with a center punch. Once you have that, a sharp drill, and cutting fluid, it is a simple matter of time. I suggest you leave the how part of the equation to the person most equipped to deal with that. This is standard structural steel work that any qualified tradesman can sort out.

 

[3DDave]

I presume the holes will be drilled before the beam is in place so the surface of the plate on the bottom is accessible.

There are magnetic base drill presses for doing this job.

http://www1.milwaukeetool.com/tools...s/compact-electromagnetic-drill-press/4270-20

You might also plan on drilling a pilot hole and then stepping up in size. This can cut the torque required by limiting the amount of material being sheared - but it works best with a magnetic base drill press.

I suspect there are also portable punches.

http://www.roperwhitney.com/portable-heavy-duty.html

http://www.nittokohki.com/tools/products/machinetools/hs-series-punches/

 

[skylite]

The metal plates have not yet been connected. I don't have budget to buy thousands of dollars of drilling equipment just for those few metal plates that I'd not do again.

I plan to just go to machine shop. Hope they have the technology to drill such thick plates. Most of their experience are just with 5mm and less thick plates.

Is 16mm base plate common? How thick do you use yours and how do you put hole in it? using your own machine or borrow from others?

 

[oldestguy]

This method probably is best, since a large drill can wander getting going. That tip also doesn't cut as well as the rest of the typical twist drill.

"You might also plan on drilling a pilot hole and then stepping up in size. This can cut the torque required by limiting the amount of material being sheared - but it works best with a magnetic base drill press."

 

[Ron]

If you have a 16mm anchor bolt, then you should up-size the drill bit to 18mm or so to give a small amount of clearance for the bolt.

I see no reason to drill these holes in the field since you are using post-installed anchors. Given that, the holes could be drilled on a drill press...a simple task...again, with proper and sharp drill bits.

 

[Brad805]

Drag them to a professional shop. They have presses that will punch out the holes in minutes. I would bet you could get those pressed for somewhere around 100-200EU (guessing you are in Europe). Some also use a plasma table (CNC controlled cutter). It will cost far less than a mag drill, and the time to drill in the field. 16mm is thin for typical base plates for structural columns I see. 19mm is a common minimum thickness in North American, but plates up to 35mm are not uncommon. It is generally more cost effective to use a thicker base plate rather than stiffeners like you detail suggests, but I have no idea of the forces you are dealing with. It is extremely uncommon to drill in the field. It is just not cost effective.

Keep in mind it is common that post installed anchors will be moved in the field due to rebar and other constraints. If you allow them to core the holes they can go thru the rebar, but a hammer drill does not. You might want to drill the bolts first if you are not going to allow them to use the torch in the field. A 4 - 6mm design gap is not uncommon for a base plate just as Ron suggests.

 

[Ron]

skylite....those are not very thick base plates. 16mm is actually a relatively thin baseplate for structural work. The flame-cut edges should be ground before installing.

 

[skylite]

again this is to emphasize the base plate will not be used as column but as rafter middle support.. again

Ill bring the 16mm thick plates to the machine shop tomorrow to see if they have the equipment to drill it.

Now id like to ask if you guys put structural epoxy underneath base plate. wont it make the base plate even stronger as it is binded to the concrete on a molecular level?

also in rafter support, the forces acting on the bolts are not uplift but sidewAy shear.. right? in typical bolt you buy in stores that are not branded Hilti, how good are the strength usually?

 

[3DDave]

I didn't say you should buy the equipment, just that appropriate equipment was available. There are rental companies.

The holes are not large and the material is not especially thick. Your description was that you'd made it to the field without the holes.

 

[Ron]

Buy bolts with supporting test data and a history of performance. Otherwise, you don't know what you're getting.

Structural epoxy will not increase the capacity of the baseplate. It is also not workable as a baseplate "grout" without adding oven dried sand as a filler. Stick with non-shrink grout.

If you are a structural engineer, you need to get serious about not compromising everything for the sake of cost and expedience. I know that sounds harsh and you might be in a country with fewer resources; however, you must push for the safety of the structure and protection of the health, safety and welfare of the public. Your responsibility is greater than that of the contractor or the owner.

 

[skylite]

Actually there are already 4 existing 16mm J-bolts of length 7" imbedded inside the corner bars inside stirrups. The middle add-on additional anchor bolts are for increase safety margin because the designer doesn't know the exact condition of the existing bolts.

For the bolts already in the column top. How am I supposed to aligned the blank metal plates to the holes and let the machine shop drill it? I plan to use Styrofoam to create the hole impression and use this over the bare plates and marking with marking brush. How do you do it?

Another thing. The contractor original plan is to use acytelene torch to make hole on the base plates.. and since the holes can be bigger than the existing bolts.. the contractor would then weld the bolts right to the metal plates holes.. what do you think of this approach?? What would be wrong with it?

The original designer said he will think about all this. He has never experienced it himself so may also ask others. We'll discuss and collaborate what we learnt. Thanks.

 

[kingnero]

It is not clear whether you're talking about bolts or all thread anchors. Either way, when the contractor mentions welding to either, this should raise a giant red flag.

I think there are, apart from those holes, other issues at your construction site that need professional attention.

 

[skylite]

It is not clear whether you're talking about bolts or all thread anchors. Either way, when the contractor mentions welding to either, this should raise a giant red flag.

That's why I am reviewing the contractor plans. I know welding the threaded bolts to the metal plate is not allowable.. but what is the reason? Is it because the welding only bind the upper part of the metal plates and there is not enough locking force for it? What else.. I need to write a report to the architect and engineers. Thanks.

 

[bridgebuster]

Some grades of anchor bolts are quenched & tempered making them brittle. If welded they can crack under cyclic loads.

BTW - would you like to borrow my drill?