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Discussion Starter · #1 · (Edited)
Finally took some time to make a new circle jig to replace my worn out one and addressed a few issues it had. I cut a lot of different sized circles daily and need to be able to switch quickly/accurately without having to measure so that was my first priority. A couple of other issues I had with the old one are that as the guide slot wore out the piece holding the sliding guide pin would shift side to side causing the bit to chatter (which in turn caused me a bunch of sanding) and I made the bit hole too large which caused a lot of tear out on certain materials since I am using a spiral up cut bit to clear the dust/chips.

The router is a Porter Cable 890 plunge with integral dust collection that works very well and I made the cursor by bending a piece of thin acrylic and scribing a line with a razor blade (I used a black marker to highlight the line). Also, I plan to replace the tape shown with dual English/metric tapes for inner/outer measurements.









The guide pin is a cut off 1/4" bolt (I tapped threads right into the plywood and used a set screw on the end to keep it from backing out) and the locking bolt is a cut off toilet bolt (I made the oval recesses for the toilet bolt with a Forstner bit). The bit hole is "zero clearance" which stopped the tear out as well as improved the dust collection dramatically and the bottom is covered with some scrap laminate that has a textured surface for easy sliding.





Depending on which way I orient the sliding guide pin assembly and which hole I use for the locking bolt I have a circle range of about 2 1/2" to a little over 28" (I will leave it in the first hole most often since that covers the majority of sizes I typically need) so I've ditched plans of making a second jig for smaller holes using my Bosch Colt plunge router. Also, if I ever need to make even larger circles I can just make a longer guide pin assembly.







The guide system was made by cutting matching grooves into both pieces and gluing some 1/8" smooth 2 sides Masonite (hardboard) into the grooves on the sliding guide pin assembly. This was a great improvement as it locks very securely with no side play and the chattering has stopped which led to extremely smooth holes.



I'm sure some have noticed that this jig is much thicker than a standard sub base plate which caused me to lose some depth of cut however it reaches a little over an inch with the bit I'm using which is more than enough for what I do (I can gain more depth if needed by going to a longer bit). All in all it has worked out very well and I wish I had done it a long time ago!
 

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Wood Snob
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Very well made and thought out fixture. I believe in and use many shop built fixtures. I have a circle fixture but I made it a long time ago and it's very time consuming to set up. I have to do trial and error to get the dimension I need. As soon as the need arises I'm going to rebuild it.

L

Nails only hold themselves.
 

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Discussion Starter · #4 ·
Very nice :) Now if there were only some scaled drawings... ;-)
Thanks! I've been meaning to try my hand at Sketchup and I'll post some drawings as soon as I figure it out.
 
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Discussion Starter · #5 ·
Very well made and thought out fixture. I believe in and use many shop built fixtures. I have a circle fixture but I made it a long time ago and it's very time consuming to set up. I have to do trial and error to get the dimension I need. As soon as the need arises I'm going to rebuild it.

L

Nails only hold themselves.
Thanks Al! I too use many shop built jigs/fixtures and most are 20+ years old so I am slowly building new ones to address issues with old/worn out ones
 

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That is one slick jig Marv. Thanks for posting

Well designed and executed.

I lack a circle cutting jig so I'm bookmarking this thread for future reference.

I'd also be interested in seeing drawings.

PS, your post was very well.illustrated, thanks.
 

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Marv said:
Thanks Al! I too use many shop built jigs/fixtures and most are 20+ years old so I am slowly building new ones to address issues with old/worn out ones
My first one was a sink cutout I made into a router table. My tool supplier said the manufacturer was thinking about voiding warranties if we used out routers that way. Little did they know.

Al

Nails only hold themselves.
 

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Discussion Starter · #9 ·
Thanks guys! I make jigs/fixtures all the time and while some are a bit more elaborate as this for tasks I know I will do again or repetitively many are very simple/crude designs for making a specific task of the moment easier/safer. Anybody else ever come across some old fixture in the shop and wonder what the heck you made it for?!
 

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Marv said:
Thanks guys! I make jigs/fixtures all the time and while some are a bit more elaborate as this for tasks I know I will do again or repetitively many are very simple/crude designs for making a specific task of the moment easier/safer. Anybody else ever come across some old fixture in the shop and wonder what the heck you made it for?!
Oh he'll yes.

Al

Nails only hold themselves.
 

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Me too. I have to label mine. For instance what its for, what size router bit, what size bushing etc.
 

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I make a one off fixture and decide to keep it because surely I'm going to do a build with this again. but it never happens.

Some of my fixtures are so old. I look at it and say, is that how I used to do that?

Al

Nails only hold themselves.
 

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Nice jig Marv and thanks for the detailed pictures. I'm with everybody here - make my own jigs and mark them for what I made them for - still can't ID some of the older ones... Back to your jig - you can't buy a commercial one that good - well done!
 

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Discussion Starter · #14 ·
Thanks Bernie! I haven't had a chance to try the Sketchup yet but I'll be making another one of these for a friend soon so I'll document more procedures with measurements (I didn't have an actual plan for this one and sized it based on the size of the scraps I had)
 
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Discussion Starter · #15 ·
The PC 890 router is making the old arms tired after using it for long sessions so I decided to make a smaller circle jig for my Dewalt compact plunge router with a different pivot pin design that allowed the base to be thinner. I need to get the dust shroud and install the tape measure/cursor before giving it a full workout however it is much lighter as well as easier to maneuver so it will most likely be my go to for the smaller circles I make almost daily.





 

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Discussion Starter · #16 ·
After getting the dust shroud I found the dust collection wasn't too great with the zero clearance 1/4" bit hole so I opened it up to 1". That actually caused dust to spew out of the slot since the 1" hole ended up clipping the edge of the channel so I had to attach a little piece of plastic to plug that up. In any case I have decided to re purpose this plunge base to a different jig so if any established member here with a Dewalt or Porter Cable compact router would like this jig just let me know and I'll drop it in the mail for you (cursor/guide pin assembly goes with it but you'll need a tape measure if desired as well as a 1/4"-20 x 1" threaded knob since I need to keep this one for the other jig)





 

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Nice jig.
I made a more basic one. I used a slot cutting bit (great for jig making) to cut a slot in the base, for the adjustable pivot to ride in. The knob (table adjust knob from dead Ridgid oss) locks the sliding pivot in place.
I cut a recess in the base to let me use router bushings, while base is on router.
 

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Discussion Starter · #19 ·
Thanks for all the interest in having this jig however I forgot to post that I already passed it on to our illustrious member woodnthings! :smile:
After getting the dust shroud I found the dust collection wasn't too great with the zero clearance 1/4" bit hole so I opened it up to 1". That actually caused dust to spew out of the slot since the 1" hole ended up clipping the edge of the channel so I had to attach a little piece of plastic to plug that up. In any case I have decided to re purpose this plunge base to a different jig so if any established member here with a Dewalt or Porter Cable compact router would like this jig just let me know and I'll drop it in the mail for you (cursor/guide pin assembly goes with it but you'll need a tape measure if desired as well as a 1/4"-20 x 1" threaded knob since I need to keep this one for the other jig)





 

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Marv does great work!

I am the happy owner of the jig that is posted here. He said "free", I said "me".... :yes:

 
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