Cooling is very important. Use cutting fluid or water.
This is one of the biggest reasons for failures.
It is very important to remove the shavings when drilling. It is best to regularly withdraw the drill and
remove shavings, and then only continue with drilling.
Once the 15mm hole is achieved, machine to the required inside diameter using a boring bar on a lathe.
Drill a pilot hole of 15mm initially
Example: A 50mm diameter hole is required.
Drill a 15mm pilot hole.
Now use a boring bar on a lathe to reach the required size.
