Well I tried to edit my entry but it wouldn't work.

Thanks to Dave and Steve Cahill for the good info

Cheers
Robert C. Fisher

To drill the hole to an exact size try a step drill:

IRWIN Unibit Unibit Step Drill Sets

John

That's a pretty cool tool, John. How do you determine the actual sizes that each of the "steps" is making? Or, how do you determine which one to buy given those odd size numbers they list there?

Argghh - just lost my whole post. Took more than 15 minutes to compose so they logged me out and everything disappeared. Here goes again.


The step drill package has the information on it. I do electronics projects often enough so I bought a 7/8" Step Drill for Metal. 7/8" being the largest hole it will make. Mine is a Greenlee 34403, but Irwin is pretty good too.
GREENLEE TEXTRON 34403 "KWIK STEPPER" MULTI-HOLE STEP BIT 7/8" (Ace has the maximum size hole description listed incorrectly by the way. Maximum is 7/8").

I bought it at either Home Depot or Lowes for around $40 USD. I would suggest you buy one locally instead of mail ordering it so you can look at the package first.

It makes the following size holes (which for me seem to work for all my projects):

3/16" (5mm)
1/4" (6mm)
5/16" (8mm)
3/8" (10mm)
7/16" (11mm)
1/2" (13mm)
9/16" (14mm)
5/8" (16mm)
11/16" (18mm)
3/4" (19mm)
13/16" (21mm)
7/8" (22mm)

It will cut through the following materials:
Steel, Copper, Brass, Aluminum, Wood, Plastic, Laminate

The double flutes make it cut through material very easily. A small round file will work if the hole is a little too tight for the part.

The sizes are not printed on the step drill bit itself (at least not on the Greenlee anyway), but either way the best way to drill down to the correct size hole is to wrap a piece of masking tape around the bit at the correct step for the hole you want, then drill down until the masking tape reaches the part you are drilling. Then stop. I use that method for holes that I drill to a limited depth using regular drill bits too.

John