Cutting A Circle While Router Is Table Mounted

[Bob Haskett]

I am starting the Thien Separator lid tomorrow. I just got my new router (took advantage of this (http://www.woodcraft.com/Product/2080385/29419/Freud-325-HP-Router-with-Precision-Router-Table.aspx) deal at woodcraft last week). I would like to know what is the best way to cut a circle while the router is mounted in the table. Also, what bit would I need?

I have seen people mention other ways to cut a circle (bandsaw which I do not have, jigsaw which I do not have, table saw which does not seem safe, etc). However, I would like to know of a way to do it while the router is mounted in the table if possible. Not sure I feel comfortable enough to do it by hand.

Thanks

[glenn bradley]

I imagine something similar to the jigs used on bandsaws could be used but, I would make a quick jig out of a scrap of thin material and do it by hand. http://www.woodworkingtips.com/etips/etip102000sn.html

[johnny means]

Straight bit and a nail is what you will need. rough cut your circle with a jigsaw first. Then you will pretty much just need to use the bandsaw technique (spin it through your cutter on its axis).

I have cut really large circles with a jigsaw hot glued to a strip if ¼ plywood . Should work for smaller ones too.

[Bob Haskett]

I do not have a jigsaw but I will in the next few weeks.

[Ben Martin]

Phil Thien has a pretty nifty jig for cutting circles, I believe he patented it also...

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

[Bob Haskett]

Phil Thien has a pretty nifty jig for cutting circles, I believe he patented it also...

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


I actually saw that, however, it states that you need to cut the circle with a jigsaw first...Which I do not have at the moment. I plan to pick up the 1590EVSK soon though.

[Ben Martin]

I actually saw that, however, it states that you need to cut the circle with a jigsaw first...Which I do not have at the moment. I plan to pick up the 1590EVSK soon though.

What tools do you have? And what material are you making the lid out of? You don't necessarily have to have a jigsaw, just something to hack the piece down to rough size. Heck, you could almost free-hand it with your router table, or a reciprocating saw, to get it down to size before using that jig. If the lid is relatively thin (ie. 1/2" or less) I wouldn't be afraid of just going straight at it without cutting it down, if you have a decent HP router.

PS. That is a heck of a jigsaw, I love mine!

[Jerome Hanby]

That's pretty clever and one more entry on my shop project list!

Phil Thien has a pretty nifty jig for cutting circles, I believe he patented it also...

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

[Bob Haskett]

What tools do you have? And what material are you making the lid out of? You don't necessarily have to have a jigsaw, just something to hack the piece down to rough size. Heck, you could almost free-hand it with your router table, or a reciprocating saw, to get it down to size before using that jig. If the lid is relatively thin (ie. 1/2" or less) I wouldn't be afraid of just going straight at it without cutting it down, if you have a decent HP router.

PS. That is a heck of a jigsaw, I love mine!

I have a table saw, 3.25 HP router, drill, jointer (that doesnt help here) and thats pretty much it. Not sure what i was going to make the top out of, probably just plywood I would guess.

[Dave Gaul]

Bob,

I made my thein separator lid not too long ago. Made the first run out of 3/4" OSB, using a jig saw to rough in, then tried to "clean up" with sanding wheels on the drill press... looked like it turned out well, but didn't function quite right! I then realized that my attempt at making the baffle part failed big time! My baffle was not the correct size and was not anywhere near perfectly round!

My solution was to re-do the baffle piece with 1/2 MDF, bought a Craftsman Cirlce Jig (Milescraft made), and use the jig & router to make the baffle a perfect circle, and make the "drop off" ring perfect as well...

I believe the cirlce jig was about $30 maybe? Doing it by hand with the jig is not hard at all. All you need is some scrap wood to elevate the piece, so you are not cutting into your work bench or table. Take light cuts, maybe 1/8" at a time to get the hang of it!

However you end up doing this, make sure you get that baffle right or it will give you problems!

[pat warner]

Would not advise making a circle, ring, or hole with a table mounted router (& no templet).
A disk, made on a router table with a pivot is sure to spin and surprise.
The load on the cutter varies as you circumnavigate; not for beginners.

What then? Pin (NO double sided tape) the blank to a templet which has the required diameter, templet rout (flush trim) and then you're in business. Use a pin router or a cutter with its bearing on the shank or on the end of the tool.
Practice with very thin stock first.

[James Evers]

I use a jasper jig for cutting circles, but I'm not sure how one could use it with a table mounted router. Maybe you could figure something out.

I use a spiral upcut bit and take a pass for every 1/4"

[Bill Huber]

I don't see why you can't just use a scrap of 1/2 mdf or plywood on top of the table. Clamp it down on one end and have a pin at the other.

Raise the router up to cut a 1/4 deep cut then raise it up a little more and so on until you have it done.

You may want to double back tape a board to the top so when the circle is cut it will still hole together not sure you would need it.

139953

[pat warner]

The work is trapped between the cutter and the pivot. In the event of an accident, the work has no place to go.
Relax your feed for a millisecond, say the jigging pulls loose, the work reverses its direction and tears itself away from its jigging, could break the cutter could throw some busted stock in your face.
A work piece and its jigging have 12 (each) degrees of freedom. 3 rotational (cc & ccw) and 3 sets of east/west, north/south, left/right.
Tape and such address very few of the immobilization issues. There are 24 possibilities!
Why put yourself at this risk, especailly when there are many safe ways to do this?

[Phil Thien]

The work is trapped between the cutter and the pivot.

Not with my jig, it isn't. :confused:

My jig isn't much different that using a circle as a template for making another circle.

[Bob Haskett]

Thanks for all the help guys. I actually made a Jig and cut my circle tonight (but not on the router table). I decided to use a scrap piece of MDF I had and cut it to the same width as my router. Then I made it 25 inches long so I could cut circles of several sizes. I then drilled holes in the end using the base plate template that came with my router so that they lined up with the screw holes. I used a forstner bit to get the screws below flush. I then drilled a 2 inch hole for the bit in the center. I then layed out the radius of the circle I needed on a larger sheet of MDF. Screwed a screw in 10.5 inches from the edge of my bit (I needed at 21 inch circle) and went to town. I started off cutting 1/8, then 1/4, then 1/2, etc until I was all the way through my 3/4 inch MDF. I had scrap MDF under it so it wouldnt go into my bench.


I learned a few things:
I hate MDF with a passion. Too much dust.
Just getting in there and doing it is the best way to learn
Router is an extremely fun tool to use
I should have used the DC adapter for the router that connects to a shop vac
And here are the pics...

[Stephen Edwards]

Thanks for all the help guys. I actually made a Jig and cut my circle tonight. I decided to use a scrap piece of MDF I had and cut it to the same width as my router. Then I made it 25 inches long so I could cut circles of several sizes. I then drilled holes in the end using the base plate template that came with my router so that they lined up with the screw holes. I used a forstner bit to get the screws below flush. I then drilled a 2 inch hole for the bit in the center. I then layed out the radius of the circle I needed on a larger sheet of MDF. Screwed a screw in 10.5 inches from the edge of my bit (I needed at 21 inch circle) and went to town. I started off cutting 1/8, then 1/4, then 1/2, etc until I was all the way through my 3/4 inch MDF. I had scrap MDF under it so it wouldnt go into my bench.

I learned a few things:

I hate MDF with a passion. Too much dust.
Just getting in there and doing it is the best way to learn
Router is an extremely fun tool to use
I should have used the DC adapter for the router that connects to a shop vac

And here are the pics...

Bob, Way to go! I'm proud of you for figuring a way to do it. Can you please post more pics showing the details of how this jig works on the RT. I can see that you did cut a perfect circle. I don't yet grasp how it does it.

Congratulations! You're going to be a fine woodworker, Bob.....

[Bob Haskett]

Actually, I did not use the router table. The jig was mounted on the MDF I was cutting, and I had some scrap under that. Sorry for the confusion.