Drilling a square hole

[pmsmechanic]

Look up "rotary broach" on youtube. SVSeeker has a good video on making one. There are probably others too.

 

[quicksandfarmer]

I'm seeing hex head bolts in a lot of places that would have used a plow bolt in the past. Round hole, use an Allen wrench on one side to hold it.

 

[sandman2234]

Caterpiller sells the bolts for their graders, and seem to be very good quality. Don't remember what I paid for them, but it must not have been too much, cheap as I am, lol!
David from jax

 

[Oldpath05]

I am guessing some of you are not familiar with plow bolts:

Similar to a carriage bolt, but it sits down inside a conical hole instead of protruding like a carriage bolt.
Commonly used to mount plow shares onto frames, etc. where a flush surface is desired.

My thoughts on the OP's problems are how much metal would need to come off to simply grind the heads flush to start with?

Since the square section is so short, it may take less time than you think to simply rough out the hole with a coarse square file.

No, just me, but getting up to speed quicker now..................

 

[texasranger556]

Have you thought about drilling round hole then squaring it out with die grinder?

How would you die grind a 3/8" square hole?!

 

[Oldpath05]

I'm seeing hex head bolts in a lot of places that would have used a plow bolt in the past. Round hole, use an Allen wrench on one side to hold it.

This gets my vote, square broaching is to time consuming, I'm slow enough as it is.............

 

[Oldpath05]

How would you die grind a 3/8" square hole?!

Use a square die bit...........

 

[CincyFlyer]

A push broach would do this; you drill a round hole, then press the broach through it, and it will cut the hole to be square. They aren't super cheap, but if you use it a lot, it would be worth it.

 

[chim]

With the amount of metal removed by the countersink, a small coarse square file might work OK.

 

[CincyFlyer]

This gets my vote, square broaching is to time consuming, I'm slow enough as it is.............

Unless you are doing this every day, you could easily do a bucket an hour with a push broach, which isn't a lot of time.