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ntyperteasy t1_j0s1gx8 wrote

I'm assuming you were trying to use something like a tapcon threaded anchor? I personally despise them. Even when I use the factory bits, they tend to jam and break off. I suggest removing the anchors and then drilling the holes out large enough to use glue in anchors. A SDS hammer drill will make quick work of it. Borrow or rent if needed.

What many commercial installers do, and will work for you, is to glue studs into the holes using special epoxy and then mount your post with nuts. If you are in the US, Home Depot sells the Hilti glue (link below) - which I have used and like - you would still need to drill holes and purchase some threaded rod of the correct diameter. Drill the hole a little oversized and then glue the threaded rod into the holes. Let it cure, then attach your posts. The exact length doesn't matter. I would use stainless steel threaded and stainless lockwashers and nuts to avoid corrosion problems.

It can be convenient to make a jig out of plywood and use that to check the spacing and location of the studs are correct before the glue sets.

https://www.homedepot.com/p/Hilti-HIT-1-Hybrid-Anchor-Adhesive-10-oz-Tube-3575547/303857797

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LegalPangolin OP t1_j0t04oy wrote

They were Titan fasteners. This is great advice, thanks so much! I’m in the US and will buy the epoxy you recommended. If we use 1/4” threaded rod (since that was the size of the original fastener) do you have a recommended bit size? I’ll definitely be renting an SDS drill too because I can’t go through that again…

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DriftinFool t1_j0t61kz wrote

One other thing a lot of people forget. You have to clean out the holes. Those bits don't clean out the hole like a normal drill bit in metal or wood. You need to blow or vacuum them out. You're 3" hole can be filled with debris in the bottom inch. This applies no matter which method of fastening you use. You especially want the hole clean if using epoxy.

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ntyperteasy t1_j0t3x0d wrote

Generally you go 1/8" larger to make sure there is room for the epoxy all around. Check the size of the mounting holes on the posts. If they are half inch, you can increase the size of the threaded rod a bit - I would go up to 3/8" rod, and drill 1/2" holes (leaving 1/8" to fill with epoxy). You want a little "wiggle room" to get the spacing of the studs right and to fill all around with epoxy. Read the Hilti instructions - they are good - and there are some youtube videos. This is a very basic video, but shows the process (you don't need the extra step shown after using a core drill - that is something unusual) - the related videos below it are also good - https://www.youtube.com/watch?v=TsonKFh0UUw

If you are doing something that is fussy, transfer the pattern to some plywood, drill the same hole pattern in that, and hold the studs in place with two nuts (one on each side of the plywood) and make sure you can get that in and out of the drilled holes without binding up. You can even leave the plywood in place during the glue cure (just don't accidentally glue the nuts or the plywood to the concrete!).

You still have the same requirements to clean the dust out of the holes, using a small brush (I stole the brush that came with one of those reusable straws my kids had to have...) and some compressed air. Vacuuming can be part of it, but it won't get the dust out of the very bottom by itself. Sticking a thin tube down to the bottom and blowing it out with compressed air is better (but don't breath the concrete dust!).

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oleorun t1_j0sp5qc wrote

This is great advice. What diameter is the best for the steel threaded rods?

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