Drilling 100 5/16" holes in steel, how?

[sandcruiser]

Hey guys
I'm modding my front gate
It has a steel frame, about 1/8" thick to which 26 boards are attached. The fellows who attached the boards the first time around used cheap screws that are rusting out and letting go.

So I'm replacing with 1/4" carriage bolts.

That means that I need to drill out 26 x 4 holes. The hole size now is smaller than 1/4", maybe 1/8? I need 5/16" in order to seat the square part of the carriage bolt.

I've got a 1/2" hand drill.

I ruined 4 or 5 old bits last week doing 6 boards. Probably user error on some, though others were just plain old and worn out anyway.

So I'm going to buy some new bits before I move ahead: I'm thinking maybe Harbor Freight step bits, since the pilot hole is already there.

Or would it make more sense to just buy 2 or 3 "decent" twist bits?

Any tips/thoughts are very welcome.

 

[Dirtsquirt]

buy a Drill doctor

I have a 750 model and it sharpens broken bits nicely

I have sharpened jagged broken. plain old dull bits etc.

worth the investment.

get to drilling. Step bits are nice to have but this isnt the applicaton for them in my view. You have predrilled starter hole
and very short drill duration per hole.
No sense dullling up the first couple of step on a stepp drill

 

[3DAMAN!]

2 or 3 decent bits are the way to go. The trick to drilling steel is to not let the bit get HOT, and to not let the bit "PLOW " threw the outside of the piece your drilling. A drill stop will help with the latter. Its just a small sleeve with a screw tapped into the side of the sleeve. It will have a hole the same diameter as the bit. Push the bit through the stop and place it against the piece so the "LANDS" or cutting edges of the bit are just barely sticking past the work piece, has to be a very small difference. I'm talking about the thickness of, say, a match book cover or less. Tighten the screw and go to town on the fence posts. If the piece is hollow , then the walls you will be drilling are not going to be very thick to start with. They will have a tendency to "GRAB" if your not holding the drill motor tightly. Also take a spray bottle full of water and spray on the bit as it is cutting to help keep the heat down. Save the adult beverages until after the job is done. Damn sure don't need a trip to the emergency room in the middle of the job Good luck

 

[Michael Hanson]

Rent a magnetic drill press,it will be steady and not break bits,also use cutting oil. Mike

 

[sandcruiser]

the nearest tool rental place that I know of is.... about 3,000 miles away.
Seriously

Ok, I'll bet that there is one in D.F. or in Panama City, maybe.

I'm stuck with what I've got, and while the job will be tedious, I'm not planning to buy new tools beyond bit(s).

My wife is in the states right now, I"ll have her bring back a couple of decent 5/16" bits, and I'll go slow/careful with some cutting oil.

Fun times ahead.

 

[Doug_S]

Try using screw screw machine or "stubby" drill bits. They have a 118 degree split point and tend to get through existing holes much easier than a regular drill. They also stay sharper longer and don't flex as much. Try Enco - Guaranteed Lowest Prices on Machinery, Tools and Shop Supplies for a source to buy them. That's where I get a lot of the supplies for my shop. I agree with the drill doctor suggestion too. It'll sharpen the screw machine drill bits just fine and split the point.

 

[nat]

Use your hand drill, set it up so you can't spin it at full RPM and use oil.

Speed is NOT your friend when drilling steel.

 

[Walton]

If you already have a pilot hole, a short 5/16 bit should go through with no problem. I buy them in a packet of 10. I'd just keep changing them, and sharpen them when I was done. I wouldn't think it would take more than 4 bits?

 

[sandcruiser]

where does one buy "stubby" or short bits? Sounds perfect. longer isn't better for this application as the steel is only 1/4".

oil. check.
slower drill. check.

now I just need the rain to pause for a few days.

 

[Chop Shop]

7.62mm is pretty close. Just get a 100 round clip for a SKS or AK and start drillin.