SteveZ writes:

Folks,

I needed a 4 7/16 hole...too small for my router circle jig
and bigger than all my holesaws.

To the router!

I'll just whip up a template and zip it out.
Now, how big should that template hole be?

I was doing some template routing for some speaker enclosures
and I needed to calculate the size of the template offset because
of the template guide OD and the size of the router bit.

Here's a quick spreadsheet that you can use...

Assumptions:
1/8", 1/4", 3/8" and 1/2" router bits calculated.
"Standard" set of router template guide sizes used.

Suggestions:
Once I made this, I labeled all my template guides
(inside and out) with a paint marker.
Using AutoSketch, you can size your template exactly,
laser print it onto 8.5 x 11" stickers and paste them
right onto your template stock for milling.

Questions?:
Please send comments, suggestions,
or whatever and I'll incorporate your thoughts.

Send to IronWood.Designs@pobox.com.

Steve


Porter Cable Router Offset Template
Number ID OD Router Bit Bit to Guide Decimal Template Decimal
      OD Clearance   Offset  
1  11/32   7/16   1/8   7/64 0.1094   5/32 0.1563
2   9/32   3/8   1/8   5/64 0.0781   1/8 0.1250
3   1/4   5/16   1/8   1/16 0.0625   3/32 0.0938
4  13/32   1/2   1/8   9/64 0.1406   3/16 0.1875
5  17/32   5/8   1/8  13/64 0.2031   1/4 0.2500
5  17/32   5/8   1/8  13/64 0.2031   1/4 0.2500
6  21/32   3/4   1/8  17/64 0.2656   5/16 0.3125
7   5/8  51/64   1/8   1/4 0.2500   1/3 0.3359
               
1  11/32   7/16   1/4   3/64 0.0469   3/32 0.0938
2   9/32   3/8   1/4   1/64 0.0156   1/16 0.0625
3   1/4   5/16 N/A N/A N/A N/A N/A
4  13/32   1/2   1/4   5/64 0.0781   1/8 0.1250
5  17/32   5/8   1/4   9/64 0.1406   3/16 0.1875
5  17/32   5/8   1/4   9/64 0.1406   3/16 0.1875
6  21/32   3/4   1/4  13/64 0.2031   1/4 0.2500
7   5/8  51/64   1/4   3/16 0.1875   3/11 0.2734
               
1  11/32   7/16 N/A N/A N/A N/A N/A
2   9/32   3/8 N/A N/A N/A N/A N/A
3   1/4   5/16 N/A N/A N/A N/A N/A
4  13/32   1/2   3/8   1/64 0.0156   1/16 0.0625
5  17/32   5/8   3/8   5/64 0.0781   1/8 0.1250
5  17/32   5/8   3/8   5/64 0.0781   1/8 0.1250
6  21/32   3/4   3/8   9/64 0.1406   3/16 0.1875
7   5/8  51/64   3/8   1/8 0.1250   4/19 0.2109
               
1  11/32   7/16 N/A N/A N/A N/A N/A
2   9/32   3/8 N/A N/A N/A N/A N/A
3   1/4   5/16 N/A N/A N/A N/A N/A
4  13/32   1/2 N/A N/A N/A N/A N/A
5  17/32   5/8   1/2   1/64 0.0156   1/16 0.0625
5  17/32   5/8   1/2   1/64 0.0156   1/16 0.0625
6  21/32   3/4   1/2   5/64 0.0781   1/8 0.1250
7   5/8  51/64   1/2   1/16 0.0625   4/27 0.1484