How can I drill a hole across a bolt?
 

Hi guys,
Might sounds like a silly question to you guys, but I really don't know :lol:
I need to drill a hole across the end of a bolt, size 5/16 . I use the cobalt bit, which is the best and it will work, according to the sales person at home depot. Well, I sat on it for a while, until my hands are sore and it still doesn't go anywhere.
A friend mentioned that I need a drill-press. To me, the drill press is only helping you to keep the drill bit straight, is that right? Or will it help to press hard on it and it will go through easier?
Thanks.

If that bolt is hardened (grade 8), you'll have a tough time drilling thru it with a hand drill. In any event, you'll want to use a high-speed 1/4" drill and filing a small 'flat' on the bolt where you want to start the hole will sometimes help.

For hardened steel like your bolt you would want about 1500 RPM on the drill bit and some drill lube that also removes heat and melts. I generally use Crisco for that unless it is tool steel then I use a special heat absorbing paste. I don't know what speed your drill turns so that could be the problem?

Time to visit Harbor Freight and get one of their drill presses, I use one of their floor models and have almost never used a hand drill for holes since. The advice for a small flat spot is correct but make sure the bit is lined up to go straight through the bolt. Good luck.

What peter said. Drill slow speed with pressure. Bit should always be pulling a chip, if not it's just skimming the surface and generating heat, getting dull.

You might check to see if there is anything commercially available to suit your needs first. There are likely bolts in the size you need somewhere out there with pre-drilled shanks for cotter-pin/safety-wire applications.
I'd probably check aircraft supply places and auto/MC race/fab shops, as well as McMaster-Carr/Fastenal.

I wonder if this is something you take to the local fabrication shop. Surely they wouldn't charge much and at least you won't have to buy a bunch of equipment you may not need.

Thanks guys,
So basically, it's is possible, but not easy, for a normal steel bolt. What about SS bolts? Forget about it?
Thanks again.

will this help?
Bolts from Aircraft Spruce

a little "V" block (you can make one out of wood) is helpful. drill press will help keep it straight but it puts a lot more pressure on the job than a drill, make sure the drill is going in the correct direction...

Lock wire?

I made a jig out of a piece of scrap aluminum to hold the bolt square and in place. Secure it with a clamp, and use a drill press.

I was drilling 10.9+ socket cap screws.

There are jobs available. Do not bother with non-USA MADE BITS. If you need just one try to buy a predone bolt.

Is your drill turning clockwise when drilled from the top? Who sharpened the bit?

This should not be difficult.

Flatten out the thread portion where you will be drilling, and peen the start of the hole. Use pressure and slow speed. I also use a cutting oil to keep the drill bit cool and cutting a nice curl.

I would assume that a good lube and a slow bit would be pretty important for this sort of work.

First you need a good drill bit (technically it's a drill, not a bit, but we're going to go with the terminology most people use.) You say you bought at cobalt drill bit, but given where you bought it, I am suspicious that it's actually what it is supposed to be. A good quality cobalt drill bit will drill through pretty much anything. Then, you need to use the right drill speed. There are charts that you can use to look up the correct speed for a given drill diameter and material. There are also formulas were you can calculate it; bottom line, for small drills most people use too slow a speed. The third thing you need is something to keep the drill cool; most people use some sort of oil that they consider a lubricant. In reality you're just keeping the temperature of the drill down to a point where it is not damaged. You do you want a certain amount of pressure, to give you a certain feed rate, but don't assume that more pressure is always better. Too much, or too little, neither one is good. A drill press helps to keep the drill aligned but it is not 100% necessary. Lastly, if you are going to drill a large hole, drill a pilot hole first. Understand that there are different drill profiles and some of them work much better if a pilot hole is drilled first.

I drill holes through bolts all of the time; hardened steel, stainless steel and titanium. The biggest factor in my success is the quality of the drill bit.

A good set of center drill bits is a smart investment. Get the hole started in the right spot and it's easy after that. Center punch the spot, get the hole started with no wobble, no slipping.

https://www.amazon.com/Center-Drill-Inserts/b?ie=UTF8&node=340049011

we used a drill press. this was a pro press that had this nozzle that sprayed a mist of liquid the entire time.

we had to cross drill a lot of high strength bolts because we didnt read the rules that all hardware without a visible nut on the end needed to be safety wired!!