How do you layout baseplate holes for drilling?

[Pixy]

Hi,

(the above are 4 baseplates with 3 painted with epoxy (for the inner side) and first few holes marked with pen and the 4th baseplate showing the unpainted side).

Do you use cardboard or big paper and punch against the anchor bolts to layout the holes in the baseplates to be drilled by the machine shop?

What are the proper way to layout it? The anchor bolt distances to edges are irregular but I found out that if I used measuring tape and mark the baseplate hole with a marking brush. The round hole is not even and the machine shop may not be able to drill it at the right distances. Tips? Thanks.

 

[human909]

Pixy. I think questions like this should be best asked elsewhere. Not in a structural engineering forum. If this was a one off I'd be inclined to answer it to help a fellow engineer out. But the number and type of questions you ask that, in my opinion, are not suitable for this forum is growing.

 

[Pixy]

It's for a column anchor bolts. I was just asking how do yo usually layout the hole.. like do you put the baseplate directly on the column and mark it or do you use films. So I need answer from practicing structural engineers. Because last time we did them, the holes were not aligned so the contractor has to hammer the anchor to make them fit.

 

[Pixy]

If you made the hole a bit bigger. During shear sideway movement, the bolts nearest the hole edge at one side can go into bearing or shear failure first because you don't engage them all simultaneously, That is why, making baseplate holes same size as the anchor bolt or 1mm larger would be more ideal.

So this is an structuring engineering issue. I'm thinking of using cardboard as guide to punch the holes in the bolts and laying it on the actual baseplates but haven't seen in the internet this done. What method do you do so all holes were perfectly aligned (to anchor bolt position) in the drilling?

 

[TugboatEng]

How are the holes on the column placed? If the column holes are not precisely placed then you'll need to assemble with the plate and use a transfer punch to mark locations. If the holes are well placed according to the drawings, then I will mark an origin, a line or a point, and proceed to place the holes in relation to the origin. Do not place holes relative to each other. If there is an error in measurement, it will double at each subsequent hole.

 

[Pixy]

The columns have already existing cast-in-sitiu anchor bolts. We just have to let machine shop drill the baseplate holes to fit the position of the column existing anchor bolts without having the contractor hammer the anchor bolts again to fit the baseplates to-be-drilled holes.

 

[Pixy]

A picture is worth a hundred words.. So how are you supposed to make new baseplate holes that are totally aligned with these anchor bolts that are already put? It's just example because I know it's too near the edge. It was an old photo before the baseplate was put and the anchor bolts hammered to align with the drilled baseplate holes. We don't want to repeat the same mistake so asking experts here. Thank you.

 

[dik]

I generally require a plywood template with the hole locations and these are used to locate the anchor rods. The plywood template matches the shop drawings.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Do you feel any better?

-Dik

 

[Pixy]

Imagine post installed chemical epoxy anchor bolts. That is, sometimes you have to drill at 3 or 4 spots to avoid rebars that blocks the chemical bolts. Here you only know the anchor bolts exact locations after the bolts are epoxied. So how do you make the template this way for the machine shop drilling of the baseplates?

 

[3DDave]

It's a shame they use formwork for keeping the concrete from running all over the place and did not use a precisely drilled plate to lock in the position of the anchor bolts.

I had a program manager "help me" that way by building a dead-weight simulator for some testing. It needed to be 30 pounds or 50 pounds and it was cheaper in concrete than getting a block of steel and then machining it. Wasting a 12 inch square piece of plywood to match the drawing I gave him was too much work so none of the bolts were even close. But, like the old shake-and-bake commercials, "He helped." <random long string of profanity>

 

[XR250]

Maybe get a piece of plywood, sit it on top and hit it with a hammer at each bolt to make a mark. Then use the marks to drill the plywood. Then lay the plywood on the baseplate as a template.

 

[dik]

Not for post applied... post applied, you take your chances.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Do you feel any better?

-Dik

 

[Agent666]

So how do you make the template this way for the machine shop drilling of the baseplates?

It should be fairly easy to drill the baseplate on site using plywood method if it comes to it.

But generally they would take each template back to the shop and match drill them.

https://engineervsheep.com

 

[TugboatEng]

Would it not make sense to drill the base plate first and use it to position the studs? If it's not welded to the column already of course.

 

[human909]

Would it not make sense to drill the base plate first and use it to position the studs? If it's not welded to the column already of course.

Well yes. Actually both would normally be constructed separately according to suitable measurements. Come on, it isn't that hard to use a tape measure!!

But nothing makes sense in this thread. But that is no surprise given the pixy's earlier threads and he is performing work in the Philippines in an sector that seems to have little planning or expertise.

 

[Pixy]

Thanks for all the tips. We were able to use cardboard (and some plywood) but aligning the edges of the cardboard/plywood to the column edges were difficult at first because the columns not perfectly rectangle.

Tomorrow we will have the baseplates drilled with the marking pen drawn on them. But we don't know if the machine shop can drill the pen marks dead center. It makes more sense if we must somehow make initial small drill indentation on the surface first? Hmm...

 

[Brad805]

In our area many steel shops send 1/8" templates to site. They have learned the cost of re-works, and they can cut thin plate like that with their high tech equipment very quickly. Another method we see is 3D laser scanning or a one man total station. One surveyor we talked with can pick up 1500 anchor bolt locations in a day. One fabricator does not produce the base plates until they have an as-built anchor bolt plan from site. I know this is likely not possible for you, but if someone has the tools there are high tech methods.