How I make my circles

[phil (admin)]

One common question I get is, "how do you make your circles."  I've just posted a preliminary page with instructions on my Thien Router Table Circle Jig.  This jig was born from a need for lots of large, [preferably] perfect circles.

To make my cyclone tops, I check the diameter of my target garbage can across three different axes (they are never perfectly round).  I average these together and make my top that size.  Then I use a rabbeting bit to cut a relief (notch) so the top sits down into the can about 1/4".  The fact that the cans are always a little less than perfectly round allows the top to "snap" into the can (basically the top brings the can into round).

http://www.jpthien.com/jpthien/cj.htm

[ndbuck]

Although I am 71, I haven't done any significant wood working in many years (high school woodshop). I m very intrigued by your trash can separator and almost as much by your circle cutting jig.

I just bought a router and router table top (to mount on a pre owned stand), so I have the tools to make both of your creations.

My question: what is the jig radius bar made of?  In one pic it looks like plywood (Baltic Birch?) but in another view the recess for the t-nut looks to "clean" for it to be ply.

Could you give me a hint?

Nelson

[phil (admin)]

You got it, just Baltic birch plywood.

[ndbuck]

Phil,

After dallying around getting my Router Table set up --and the inevitable "honey do's" I am turning my attention back to the circle cutting jig.

I am not sure what I am seeing (because of the camera angle on the first picture (of the 4 at the bottom) ):

Is that a "traditional t-nut" in the recessed slot (on the opposite side of the jig from the Knob)?  If so, did you grind off the tangs?

The other possibility, I perceive, is that the nut in the recess is one of the oval nuts sold by woodcraft in 10 packs --- but ----- I only found two choices on the website  #147921 [10-32's] and #147922 [1/4 -20's] neither of which jive with the 5/16" modified all thread.

Help <grin>

Nelson 

[phil (admin)]

Try searching the Woodcraft site "130441" (without the quotes).  This should bring up the part I used.

The Woodcraft web page needs an overhaul, they categorize things and the search results often require lots of clicking to find what you're looking for.

[ndbuck]

Phil,

Thanks very much for the Woodcraft #.

Interestingly I've been looking for that same nut for a while -- for other purposes having to do with the Router table.

I had no success at Rockler and a local "Shasta Fasteners" store.

Now I will have to get familiar with Woodcraft and find something else to buy so that I don't have to spend $7.00 to get $2.00 dollars worth of nuts. <grin>.

Thanks, Nelson

[memilanuk]

Phil,

Thanks for this tip!  Coulda used it earlier  ;)  I used a router trammel jig that came w/ my Bosch 1617 EVS router to cut the circle... this has the downside of having to go around and around and around and around, lowering the bit a little each time.  Gets kind of monotonous, and the darned cord always gets tangled up to boot.  Being able to do a 'quick-n-dirty' cut w/ the jigsaw was something I hadn't quite thought of (it'd probably work even for the way I have been doing things), and being able to use the flat surface of the router table top should make life even easier.

Thanks again,

Monte

[boisejim]

I was wondering if you could explain the actual process of cutting a circle.

So once you set the Radius and start the cut I assume the following:

One hand firmly holds onto the Jig and puts slight pressure against the bearing of the cutter.

One hand spins the workpiece slowly into the cutter (counter clockwise).

Is the workpiece stedied by having a fence, block or pin to hold it against while cutting?

[phil (admin)]

You've pretty much got it.  I don't use a starter pin or anything like that.

I use the jig and a pencil to mark my circle on my workpiece.  I rough cut the circle on my bandsaw or a jig saw.  I put the jig back on the workpiece and go at it on the router table.

At the router I've found that it is easier to turn the workpiece under the jig while I also spin the workpiece and jig around the bit.  Once you've done it once or twice it actually becomes very natural.

It is important that you can hold the workpiece solidly in your hand, BTW, to prevent it from spinning.  The circles I make are all large enough that they hang over the side of the table.  Holding them firmly while applying downward pressure on the jig does the trick.

[boisejim]

Thanks Phil.

You are AWSOME!

[Dougp28704]

Very nice jig. Great idea. Wood working magazines should pay you for ideas.

[sailfl]

I hope to make modification for the Top Hat design.  I currently have a baffle in my HF dust collector.  I recently bought a Shop Fox 3HP.  I will be using my CNC machine to cut the parts.  I think I will use Sintra (PVC) inside the Top Hat.