Drilling in metal? oil, etc.

I need to drill a hole in the side and top of my mopeds (Tomos) oil drain and oil fill bolts in order to connect safety wire.

I have tried 3 times to drill a hole in the bolts side and each time I am off-center just a small amount.

The metal seemed very hard in comparisson to the drill bit?

What type of drill bit to use? Cobalt, Titanium, etc?


I used a High-speed steel bit, 1/16"

What can be used for cutting liquid?

Thanks for you help.

maybe I will buy new bolts with a taller top and hopefully hit the "center" point.

Re: Drilling in metal? oil, etc.

First you need to use a center punch. You place it where you want the drill to start and then hit it with a hammer. This will give the drill bit a guide so it doesn't walk. The drill used should have reliefs cut in the backend so it can start a hole with the least amount of metal contact, it is called a starting drill.

Looking at the cutting end, you have two flutes. They are at 30 degrees angle. At the center where they both meet you will see the reliefs cut in so that the two cutting edges go right to the center. A regular drill that is used to enlarge an existing hole will have a diagonal line intersecting the two cutting edges. You can grind the relief in them on a grinder if you have one. The two flutes need to be good and sharp and of equal length.

The bolts are a stainless steel so they are harder than the aluminum parts. Use a varible speed drill motor and do not run wide open. Practice on an old bolt to get the hang of it. They make a cutting oil for tapping and drilling, it is called "Cool Tool" . Generally if you control the speed you can drill without it.

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