# inlay bushing math



## falconcrest woodworks (Aug 23, 2010)

I am using the porter cable style router bushing set and am new to inlays and how to figure out how to rout a 3" relief in a table top for a 3" diameter inlay.
I'm sure the first piece of business is to make a female template then use that and the proper bushing to route the relief but the math escapes me. Can any one give me a 
push start?
Thanks, Mike58


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## bobj3 (Jan 17, 2006)

Hi Michael

This should help
Router Workshop: Inlays
Router Workshop: Inlay tip


http://manuals.harborfreight.com/manuals/99000-99999/99552.pdf
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Mike58 said:


> I am using the porter cable style router bushing set and am new to inlays and how to figure out how to rout a 3" relief in a table top for a 3" diameter inlay.
> I'm sure the first piece of business is to make a female template then use that and the proper bushing to route the relief but the math escapes me. Can any one give me a
> push start?
> Thanks, Mike58


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## Hickory (Oct 25, 2005)

Thanks for the help, I see how it works now....


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## Acebetter (Nov 14, 2015)

Hi Mike, I think this formula is correct. Just solve for the one unknown that you want. The inlay circle diameter equals the template diameter less one half the outer diameter of the bushing plus one half the diameter of the router bit. I have the same problem to solve, I need a 2 3/8" inlay circle.


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## Mike (Nov 22, 2004)

This thread is from 2011 and BJ (BobJ3) passed away. He took delight from helping forum members with problems like this. I miss the stinker.


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## Cherryville Chuck (Sep 28, 2010)

Welcome to the forum Ace. The posts you are replying to are over 4 years old. There is a date at the top left corner of all posts. The simple formula for the offset is the OD of the guide bushing - the diameter of the bit divided by 2. Ex.- a 1" guide - a 1/2' bit will give a 1/4" offset. 1 - .5 /2= .25

There is an exception to that. If you were cutting a circle out and keeping the center round. If you went around the inside of a circular template with the same setup as above then your bit would be offset from the template by that 1/4" then you would add the diameter of the bit. Ex.- 6" round template - 1/4" offset + 1/2" bit = 3/4" . You would wind up with a 5.25" circle in the center.

This all may seem complicated but if you make a drawing of the parts it is actually very simple when you can see it.


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