Router template guide--how to use?

[Chris Yarish]

Ok, so my grandpa had a bunch of router template guides that were left in a toolbox in a house he bought. He has given them to me, but aside from the really obvious function that they perform (to use as a guide on a template...duh), how are they used, what bit is used with them and what significance is the outer diameter and inner diameter listed on the package. There were probably 10 of them, all different sizes....I would like to possibly put them to some use, but have no clue when or why I might use them.

Thanks.

[Jamie Buxton]

You've got the basic concept. You mount the guide to the router. A bit sticks through the guide. You run the guide against a template. That's it.

I use them for many operations. Here's several:

Boring shelf-peg holes (with a plunge router)
Some dovetail jigs use template guides
Inlay work
Machining through-mortises
Making many identical parts

[Chris Yarish]

For cutting identical pieces, how does this differ from using a flush cut bit?

Also, I have seen some inlay work done with a router. Couldn't really get my head around how it all worked...it was on a TV program and I did not record it. Once it was over, I was just scrathing my head not sure how to set it up, or what bits/template guide to use.

[Anthony Whitesell]

I wonder the difference as well.

The one difference I have figured out is that the bushings will not wear out whereas the bearings can wear out, clog, or jam.

[Tom Veatch]

...what bit is used with them and what significance is the outer diameter and inner diameter listed on the package. ....

Inner diameter is the largest (straight) bit that can be used in the template. Outer diameter gives you the information needed to figure the template offset.

The offset will be equal to the difference between the guide radius and the bit radius. I.e., assume a 3/4" OD on the guide and a 1/2" bit diameter. The edge of the cut will be offset from the edge of the template a distance equal to the difference in radii: (3/4 - 1/2)/2 = 1/8". That offset must be considered when making a template to use for template routing.

The major difference between using a template guide and a template or flush trim bit is the offset. Typically for a bearing guided bit, the offset is zero. With a template guide, the offset is non zero.

There are some other considerations - how well is the guide centered on the router bit axis, how much does the guide deviate from being a true circle, etc., which affects the accuracy of the finished cut, but the major influence is the template offset required with the guides.

[Jamie Buxton]

One difference between a bearing-guided bit and a template-guided bit is that the template guide may not be exactly concentric with the bit. Whether it is concentric depends on the construction of your router, or in some cases how you've adjusted the base on your router. Typically the non-concentricity is less than .01", and so may not matter to you.

[Roy Wall]

For cutting identical pieces, how does this differ from using a flush cut bit?

Also, I have seen some inlay work done with a router. Couldn't really get my head around how it all worked...it was on a TV program and I did not record it. Once it was over, I was just scrathing my head not sure how to set it up, or what bits/template guide to use.

Chris,

The flush cut bit has a bearing exactly the size of the cutter - this bearing will 'ride' on the master template - the cutter mirror the template.

Like Tom said - the bushing guides (for templates) just create a certain amount of space away from the template......but still copy perfectly.