drilling problem question HELP! : )

Hi all, I am trying to drill 7/32 holes for pop rivets in 20 ball cap tops for fence post for our new wrought iron fence. Thye posts are 2"x2" 14 guage steel, the ball caps have a box bottom that fit over these post tops. The fencing came from fence-depot dot com and I assume all the parts came from China. I was originally was going to buy a cheap stick welder to attach the ball caps to the posts but realized I would probably make a mess out of the paint trying to get a good electrical connection for the welder, the extra heat would also screw up some of the paint. I decide I can drill and pop rivet these onto the fence posts much easier. SO, I go and buy a set of Dewalt bits with the titanium coating. I was able, with much effort, to drill a few holes before dulling out the bit. I had to apply excessive force with my drill press to get through the first millimeter or 2 then it went through relatively easily. I tried smaller pilot bits which also acted like i was trying to drill throug a lock or some other very hard (case hardened?)steel. I went back to Home depot and spent like $30 on a set of Rigid cobalt bits. They were no any more effective in getting through the harder outer layer of the cheap ball cap post tops.
I always used oil when I drill to preserve sharpness of my bits ... I am at a loss here... I have drilled though quite a few different material in my life.... i reminds me of trying to drill though hardened lock bodies. These post caps were only about $2 each, I am wondering if the sides of the box part of these ball caps I am trying to drill through came from tool steel scrap or ????? I have never had a problem like this before. any suggestions? I am thinking of going back to the welder idea...I am sure that welding will have it's own set of problems!

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Cast iron? the carbide inclusions are very off putting to a drill.
My experience with redrilling a vice body for jaw soft faces was also depressing - so that I started thinking about the possibility of microdiamond inclusions due to carbide squeeze. (This WAS an ealy method of diamond production - but now the hydrocarbon/plasma method works so much better.)
Brian Whatcott Altus OK

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Probably high carbon, akin to bed frames and rebar-all sorts of scrap used to make it, no real controls over the composition. Low RPM, use oil. Some parts may drill easier than others...
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Dear DTL:
DTL wrote: ...
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If the caps aren't painted, you could heat them with a torch and let them slowly cool... maybe you can take the temper out of them. Cold forming might be part of the problem.
You could drill the hole in the post, and use a hammer and punch to displace metal from the cap into the hole. Of course if it is high-carbon, you could shatter /crack the cap.
You could use epoxy to adhere the cap to the post, after suitably roughing the paint (and cleaning the dust off) on both both mating surfaces. You could use silicone rubber adhesive... same way.
If the caps are made from high-carbon "trash", it is very likely they will be prone to rusting.
David A. Smith

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I agree with the above, specifically RTV Blue. Works wonders as a glue.