what size of the Copying ring do I need for my my dovetail bit?

[asmirnov]

Hi,

I have not done much dovetailing before so please bear with me for the minute. I need to make a few dovetails, I have a Festool dovetail router bit 490991, size 14.3 mm. I need the copying ring. I am wondering is there is a dependency between the size (the width) of the dovetail (in my case it is 14.3 mm) and the size of the ring?
There are different sizes of the rings - 8.5, 13.8, 17, 24 and so forth. So whic hone should I choose?
Or in other words what does the size of the ring mean - would that be the distance between the dovetails?

Thank you much for your patience.

Anatoliy

 

[Jerry Work]

Hi Anatoliy,

You do not need a copy ring unless you are using a template fixture with a dovetail bit.  If you are referring to making dovetail cuts with a template or dovetail jig, then you need to use whatever the jig manufacturer specifies for their jig, dovetail bit and template.  You cannot deviate from what they designed.  You also cannot deviate from the thickness of work pieces they specify for their jig, bit and copy ring or your joints will not fit.

In general, to figure out how any router bit will cut with any size copy ring when run against a straight edge, start by drawing a circle on a piece of paper the same diameter as the router bit.  Now, using the same center point draw another circle on the paper the same diameter as the OUTSIDE diameter of the copy ring.  The cut made by the router bit (no matter what its shape) will be along the line the inner circle makes when the outer circle is drawn along a straight line.  That will be 1/2 of the difference between the diameter of the router bit and the diameter of the copy ring away from the straight edge the copy ring is held to while the router is moved along the straight edge.  For example,  if your inner circle is 20mm in diameter and your copy ring outside diameter is 30mm, the the cut made by the router bit will be 5mm away from the straight edge.

I'm not sure what your actual question is, but hope this will help.

Jerry

 

[asmirnov]

Thanks, Jerry,

I think you answered my question.
I don't have the template, you were right, I was thinking about making one myself because for my small project I was not gonna spent $400 on the VS600 dovetail jig. That's why I wanted to figure out the sizes. But I looked around and I see that there are other jigs available much cheaper so instead of making some homemade I think I will be able to find one that meets the budget.  [wink]

Thanks for your help.

Anatoliy