Online they have charts it will tell you what number or size of drill bit and what corresponding pin size

 

Use a roll pin punch as well if you have one.

 

If you have the room a little bit of lead in will help get the pin started.

 

I/16" roll pin is what most of us use John. 1/2 the thickness of the sight blade. And a 1/16" drill will work.

 

Note that one end of the 1/16" roll pin most likely has a chamfer, the other end is blunt. Put a drop of oil on the chamfer end and start it into the sight hole by hand. I use a nylon head hammer or nylon sight punch. Once it's started use a 1/16" roll pin punch to drive it flush to the top of the sight. A regular punch may damage the blunt end of the roll pin but a roll pin punch has a nub on the end to prevent damage to the roll pin. They're not expensive, available through amazon or most hardware vendors.

Check to make sure the chamfer end doesn't protrude into the slide to far or it may interfere with the bushing (?).

 

Well after installation of 3/32 roll pin in stainless trp I drilled the hole and Mary installed the pin. My essential tremors made it damn near impossible to hold the punch and hit it with a hammer

 

I ordered 1/16 roll pins from Brownells

 

I'm thinking of adding Mary to the gunsmith list. When my hands start shaking she reluctantly has to help