Router Bit Recommendation to Cut Circle with Router

[George Bokros]

I am going to make a table top using the router to cut the circle with a router compass and am wondering what type of bit to use. I am thinking a combination up cut / down cut spiral bit. What would you recommend??

Thanks

George

[Mel Fulks]

SINGLE flute 1/2 inch .Cuts fast.

[Steve Rost]

You have a lot of things to consider, how powerful is your router, the depth of your cut, is it solid wood, or plywood? A little more info and we can zero you in. Over all, I have had good luck with spiral cut bits. My only problem was not tightning the collet enough and the bit pulled itself out of my router.

[Bruce Wrenn]

I've used a combination of bits to do this. First, in your trammel bore a hole that will allow you to use a 5/8" guide bushing, instead of mounting base solidly. This way, you can pivot router so your grip is comfortable. I use a half inch shank 1/4" two flute bit (Woodcraft $5 bit of old,) and route to about 1/4 - 1/2" depth. Then using jig saw cut around top in groove created by router. Then pattern bit (1/2 shank X 3/4 dia cutter, also a Woodcraft $5 bit) clean up cut using routed area as a guide.

[Rick Fisher]

Did one last week.. Used a 1/2" spiral router bit and made a few passes.. worked fine.

I made a template because I didn't want to risk the wood used for the top, but a template would not be needed if I was more comfortable with it ..

Here are the pictures..



The plywood template was made with jig attached to the center.. spinning the router around .. cant remember the word..



The bit I used is actually a 2 flute end mill ..



Circle.

[Murray Roblin]

I use a half inch shank 1/4" two flute bit (Woodcraft $5 bit of old,) and route to about 1/4 - 1/2" depth. Then using jig saw cut around top in groove created by router. Then pattern bit (1/2 shank X 3/4 dia cutter, also a Woodcraft $5 bit) clean up cut using routed area as a guide.

Bruce,
Curious - Why go through two steps? Why not use the trammel to finish the cut?

Thanks,
Murray

[George Bokros]

You have a lot of things to consider, how powerful is your router, the depth of your cut, is it solid wood, or plywood? A little more info and we can zero you in. Over all, I have had good luck with spiral cut bits. My only problem was not tightning the collet enough and the bit pulled itself out of my router.

The top will be solid cherry 3/4" thick. My plunge router is a 1.25hp Dewalt.

Thanks

George

[George Bokros]

Ooops double post.

[Curt Harms]

Jasper jigs are intended to use with 1/4" cutters, at least the printed diameters work out that way. Just don't try to cut all the way through 3/4" in one pass.

[Prashun Patel]

If you're using a trammel that will be screwed to the underside of the circle, then I'd use a spiral upcut. Many shallow passes. Any 'lesser' big risks tearout around the side grain and can be hard to plunge. The spiral upcut will help with chip ejection. It should also leave a cleaner line on the other side.

However, I only own a spiral downcut, which honestly is fine too. You just have to pause every now and then to clean out the groove, or move back and forth so the chips are blown out. Also, any tearout on the top edge is minimal and is easily cleaned up by the edge profile you put on after.

[Mel Fulks]

I just looked up that jasper thing .What advantage is there to something that slow? A single flute 1/2 inch bit would do it in 1 or 2 QUICK cuts.

[chris renfrew]

How big of a circle are you trying to make. I came in here to mention "Jasper Jigs" and it looks like Curt Harms beat me to it. You can always make a jig that pivots around a center point if you don't want to spring for the Jasper.

I use the Jasper Jig with my Bosch 2.25hp router with a Freud (75-102) 1/4" Double-Flute Up Spiral router bit.

[George Bokros]

I plan to cut from the top of the blank by using double stick tape to stick a block to the center for the center point so I do not get a hole from it. I know I will have to add to the bottom of the compass the same thickness as the center block so the router sits square to the table top. I also plan to rout a circle just inside the edge using maybe a core box bit that is why I want to work from the top.. I am not sure yet if the edge will have an edge profile on the top edge or the bottom edge so I need to prevent tear out if possible.

I am making a 16 to 18" table top.

I ordered the Lewin router compass and looks like the got the last one because they are now out of stock and it has been shippped, UPS acknowledges having the package.



Here is link to the compass http://toolsandmore.us/bighorn26100-...ercompass.aspx


George

[chris renfrew]

I have one of those Lewin compasses as well the Jasper Jig. They work well (not quite as well as the Jasper).

Have a nice sharp bit and go slow to avoid tear out. Several passes will be necessary for your thickness.

[Bruce Wrenn]

Bruce,
Curious - Why go through two steps? Why not use the trammel to finish the cut?

Thanks,
Murray

Comes from years of making the circle, as table top, and making the "hole, as in speaker boxes." Once I built a radiused desk that was twelve feet long, using 3/4 plywood for ribs. It was much easier to route part way, remove waste and then finish with pattern trim bit. Largest radius I ever did was a platform for a pulpit. Radius was about 40 feet. Set up benches in middle of room, then using threaded rod and coupling nuts made my trammel. Only needed a quarter of the arc.