Tip #91
How to Counterbore For Screws
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Operations:
Let us countrebore 1" deep for 1-1/2" - #10 flat head screw.

1. Prepare a piece of stock 3/4" x 1-3/4" x 7-1/2".

2. Scribe a longitudinal center line on one edge of stock. Intersect this line with four equally spaced squared lines. Make punch marks at the four intersections.

Fig. 2 Click image for larger view.

3. Secure 3/8" twist drill bit in chuck.

4. Place side of stock against fence and position right hand punch mark under point of drill bit.

5. Drill four holes 1" deep.

Note: When setting depth dial with a twist drill mounted in chuck, be sure that lead point of drill bit is embedded in punch mark and lips of drill bit are touching surface of stock. The limit of travel of the flutes determines the bottom of the hole.

6. Replace drill bit with one of size 3/32".

7. Place scrap under stock to be drilled.

8. Drill four lead holes in the center of the counterbores to a depth of 1".

Fig. 3 Click image for larger view.

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