# cutting 3" circular recesses



## Grung56 (Jul 13, 2010)

Using a dish carving bit (from LV #16J26.70), I have to route 1/16" recesses in perfect circles. 

If the photo upload cooperates, you can see my prototype (done with Forstner bit). But maybe I need more posts first.

I plan to use guide bushings inside a template that I can cut with a fly cutter on a drill press. So, I can make the template any size I need. (There could be some trial and error involved!)

Do you think I can use a guide bushing smaller than the outside diameter of my router bit (1.25")....IF I size the template accordingly?

Thanks.... Greg


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## bobj3 (Jan 17, 2006)

Hi Greg

That will work with the template but than you must find a way to hold it down in the right spot, I would suggest the Forstner bit like you have done but then use a cir.jig to put the 1/16" in place, the Forstner bit did the work for you by marking the pocket spot on dead center..just drill a small hole (1/8" ) for the pivot point and plunge the router down to do the work..  I would suggest the cir. jig below for the job..they cut a very true cir. every time..

Amazon.com: Jasper 200J Model 200 Circle Cutting Jig for Plunge Router: Home Improvement

Amazon.com: jasper circle jig Home Improvement

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Grung56 said:


> Using a dish carving bit (from LV #16J26.70), I have to route 1/16" recesses in perfect circles.
> 
> If the photo upload cooperates, you can see my prototype (done with Forstner bit). But maybe I need more posts first.
> 
> ...


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## harrysin (Jan 15, 2007)

Grung56 said:


> Using a dish carving bit (from LV #16J26.70), I have to route 1/16" recesses in perfect circles.
> 
> If the photo upload cooperates, you can see my prototype (done with Forstner bit). But maybe I need more posts first.
> 
> ...


Welcome to the forum Greg, unfortunately it isn't possible for the template guide to be SMALLER than the cutter, the latter having to pass through the former with some clearance. The method for calculating the size of hole in the template is:
decide on the size of template guide, the bigger the better, also the size of cutter, the simple formula then is: O/S diameter of guide minus diameter of cutter plus the size of the hole that you want. If you want to use a 1.25" cutter you will need a guide at least 1.5" diameter and supposing that you want to rout a 4" hole, then, 1.5"-1.25"+4"=4.25" hole in the template. If perhaps your largest template guide is 1.25", then use a 1" cutter and we now have: 1.25"-1"+4"=4.25"! No magic here Greg, the DIFFERENCE between cutter and guide in both cases is the same, 0.25", if we divide this by two, we refer to the OFFSET being 1/8". I do hope that this makes sense to you, if not, keep asking.


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## Grung56 (Jul 13, 2010)

Thanks BobJ3 and Harrysin
First BobJ3, With the Jasper guide jig, could I use a bit that is 1 1/4 " in size?

Harrysin, if my bit is 1 1/4, is there such a thing as a 1 1/2 guide bushing? or have I misunderstood you?

Thanks to both..... Greg


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## bobj3 (Jan 17, 2006)

Hi Greg

Yes the Jasper can take on the 1 1/4" router bit, the picture below shows one of the jaspers to take on the 1" bits, copy made of 1/2" MDF, I will post one of the jasper to take on 1 1/4" router bit easy.. if you want to see a snapshot just ask..  it's a very easy rework job on the jasper jig. The 1 1/2" brass guide is the key.. in that way you don't need to bolt the jasper to the router base, just drop and cut thing...

1-3/4" Brass Template Guides - Lee Valley Tools

Oak Park Enterprises Ltd.: Catalogue

Router Forums

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Grung56 said:


> Thanks BobJ3 and Harrysin
> First BobJ3, With the Jasper guide jig, could I use a bit that is 1 1/4 " in size?
> 
> Harrysin, if my bit is 1 1/4, is there such a thing as a 1 1/2 guide bushing? or have I misunderstood you?
> ...


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## harrysin (Jan 15, 2007)

Greg, I personally use a 40mm guide wherever possible but I'm led to believe by Bobj3 that they aren't generally available in the US and Canada. On many occasions on this forum I've suggested that members DEMAND 40mm guides from suppliers /manufacturers, the 40mm being 1 37/64" but 1.5" would be fine so why not push suppliers/manufacturers for the 1.5". It puzzles me that a/the leading country like America haven't yet realised the benefits of a guide as large as 1.5" or 40mm, some of which are: a bigger variety of cutters can be used, it's possible to SEE what the cutter is doing, the dust doesn't build up, compress and cause extra heat build up on the cutter, projects started with a large cutter like patterns on a box lid, can then have identical concentric/parallel patterns routed going down in size two three of four times if the cutter is small.


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## RustyW (Dec 28, 2005)

Hey Greg, here is a link to a project I made using a dish cutter and large guide. My guides are from Lee Valley. Hope this helps.

http://www.routerforums.com/guide-bushings-templates/14662-coasters.html


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## jw2170 (Jan 24, 2008)

harrysin said:


> Greg, I personally use a 40mm guide wherever possible but I'm led to believe by Bobj3 that they aren't generally available in the US and Canada. On many occasions on this forum I've suggested that members DEMAND 40mm guides from suppliers /manufacturers, the 40mm being 1 37/64" but 1.5" would be fine so why not push suppliers/manufacturers for the 1.5". It puzzles me that a/the leading country like America haven't yet realised the benefits of a guide as large as 1.5" or 40mm, some of which are: a bigger variety of cutters can be used, it's possible to SEE what the cutter is doing, the dust doesn't build up, compress and cause extra heat build up on the cutter, projects started with a large cutter like patterns on a box lid, can then have identical concentric/parallel patterns routed going down in size two three of four times if the cutter is small.


Harry, 

with the OP busing set, the largest guide is 1.5".

I have just attacked my Rockler ellipse jig with a 1.5" forstner bit so I dont have to attach the router to the jig...

Thanks for the tip, BJ....:sold:


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## Grung56 (Jul 13, 2010)

Bobj3
I guess to each of us a mystery exists until it is revealed. So it is with the Jasper jig.
I don't quite understand how I would get a flat bottom recess when I have to have a hole for the pin, around which the jig rotates.
RustyW had a neat idea for a jig that does not require pins or double sided tape to cut recesses.


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## bobj3 (Jan 17, 2006)

Hi

A very small 1/8" dowel pin will plug that hole in a heart beat, so small you may not see it at all  with some glue and saw dust mixed from the same stock..to glue the dowel pin in place..

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Grung56 said:


> Bobj3
> I guess to each of us a mystery exists until it is revealed. So it is with the Jasper jig.
> I don't quite understand how I would get a flat bottom recess when I have to have a hole for the pin, around which the jig rotates.
> RustyW had a neat idea for a jig that does not require pins or double sided tape to cut recesses.


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