Drilling a hole for to install a 1/4 inch grease fitting, I will also need to thread the hole?

Question

What size drill bit do I need

Answer 1

1/4" zert (or zerk) fittings (AKA grease fttings) come in three standard threads: pipe, UNF straight(28 TPI) and UNF tapered (28TPI).

Answer 2

For a 1/4" by 20 thread you'll need a #7 drill bit.

Ref this web site for Drill / Tap Chart

http://www.shender4.com/thread_chart.htm

Answer 3

Look around before you worry about threads. Ask for a drive in or push in zerk. They do make them and it would be easier just to drill a hole and drive in a zerk.