Flame Drilling:

Flame drilling is utilized to make relatively shallow holes in bars or heavy steel sections. Such holes can be utilized for centring massive pieces of steel in a lathe or inserting tools for creation of seamless pipe. The operation is similar to making a piercing begin in a plate. Use straight-bore tips. Continue the hole till you think it's deep sufficient. It is very hard to drill a blind hole to a precise depth by using this method.