How do you route large arc/circle, e.g./ >4' or 5'?

[woodwreck]

The thought has come to mind - please enlighten me - Having read Brice's outstanding manual on the MFS system and particularly circles and arcs, - how do you route an arc or semi-circle that is greater than perhaps 4 or 5 feet diameter, such as an arch over a door or window? If the arch has a rise of illustratively  24" - 30" over a door, the arm length to swing a router (rather than an edge guide) would have to be something on the order of perhaps 7 or 8 feet for the partial circle. Do you just keep extending MFS rails or use some other means? How would you guys in the real world do it?

This has nothing to do with any prior discussions of the product - in general terms what method is used?

TIA

 

[nclemmons]

No reason you can't attach two pieces of MFS to the ends of a long 1 x 4 or a narrow piece of plywood.  It's relatively easy to drill a couple of holes on each end and use a bolt and nut to secure the MFS.  That gives you a very long potential length with the smallest of the MFS kits.

I've done arcs with the MFS but not of the size you asked about.  But I'm confident you could easily extend and make it work.

I recall reading somewhere about someone who was making a large counter if I recall correctly - and the arc was maybe 30' radius or more, and it worked great.

neil

 

[woodguy7]

Just make your own from a long strip of plywood.  Draw a line down the centre & screw the plywood to the bottom of the router.  Done it many times & it works a treat.  Can do a radius of 8ft no problem.

Woodguy.

 

[Deansocial]

dont screw it to the ply, drill a hole the same size of a guide bush you have that way the router does not have to be in an uncomfatable poition when you are cutting

 

[Brice Burrell]

I suppose you could add MFS profiles (remember Festool has the profiles in one and two meter lengths) but that's not how I would do it. I'd just use a long, narrow rip of plywood with a hole the size of the guide bushing and pivot point at the other end (I believe that's what Dean was saying). Simple, fast and inexpensive. 

 

[Chris Hughes]

I just cut an segment that the radius was 22.4' long.  I bought a 20' 2x4 and attached my 6' radius jig that I had made.  Easy enough to do but stuff that long is always a pain to set-up.

 

[Deansocial]

yep, thats what i meant brice.

i mae this using that method(yet to finish like most jobs on my own place)

 

[jonny round boy]

yep, thats what i meant brice.

i mae this using that method(yet to finish like most jobs on my own place)

Aah, It's you, Chip!

[welcome]

Nice to see you finally climbed aboard the 'green' train!!!

 

[Chris Hughes]

Pretty cool concept on the entertainment.  I would have never thought of that application.  Trippy dude.

 

[Deansocial]

yep, thats what i meant brice.

i mae this using that method(yet to finish like most jobs on my own place)

Aah, It's you, Chip!

[welcome]

Nice to see you finally climbed aboard the 'green' train!!!

yeah, its chip. Surfing under my other alias

 

[greg mann]

Actually, I think that entertainment center may be straight and square and photographed with a fisheye lens. [poke]

 

[harry_]

That's cool, awesome concept and execution!

 

[Eli]

I recall reading somewhere about someone who was making a large counter if I recall correctly - and the arc was maybe 30' radius or more, and it worked great.

To be honest, I made a counter with a 36" plus radius with a piece of string and pencil and used a short guide rail and TS75 to cut all the waste off it. That was plenty clean enough to belt sand.

 

[Chris Hughes]

Eli, I try to never freehand if I can help it.  I'm a jig guy so even if the radius for the segment was 60' I'ld find a peice long enough to make a jig to make the pattern.  So guys are great freehand, I suck. 

By the way if anybody is interested, If you have a partial radius, a segment, and you want to know the radius the formula is very simple.  The two givens are (x), the cord or base of the segment and the which is the rise of the segment or the part of the radius that is measurable. 

(x/2)squared +y squared over 2y

So if you are making a radius toe kick and you want to make it using a jig and copying ring grab a stick of wood to mount your router to and use the formula above.  Its pretty easy.

 

[Eli]

I'm dreadful freehand.  [big grin]

That's beside the point. I used a 1080 straight rail to trim waste to the (curved) line and a BS75 to smooth it. The radius is so wide the flats are actually longish and the angles to remove by sanding very obtuse. It surprised the hell out of me how well it worked. The bartop was too deep (65mm) to rout and the jigsaw blade wanders out of plane. So the TS75 was really the best option.