Help!!!!!!! Circle cutting with the MFS 400

[TahoeTwoBears]

Hi all,

I just wiped out a few hours of work with my clumsy attempt at cutting a circular table top out of alder. I was happy with the joining with the saw and rail trick, my glue up went well, but the circular cut just killed all of that and about $90 worth of alder. The new catalog states that the max circle you can achieve with the MFS 400 is 34". When I "captured" the circle insert within the MFS, there didn't appear to be any way to make the radius 16" (what I was after). I read a few of the tutorials and took a look at a bunch of the pics and hooked the insert to just one extrusion. That gave me the needed radius, but as you might guess, the insert slipped about 3/4 of the way around the circle.

Time to start over. Any thoughts on how to properly get to 16" with the 400?

Mike

 

[Brice Burrell]

Mike, The MFS is designed to have the circle cutting pivot fit into the first slot of the profile, the slot closest to the inside of the profiles. You can see in the pic that is where I'm installing the pivot, if you put it into the slot farthest from the inside, where the arrow is pointing you'll get a little bigger of a circle.

EDIT:  I forgot to add a couple of things, first, you won't be able to use the scale on the proflies to set the size. Second, 14" radius or so is about as big a circles as you can get, not 16".

 

[TahoeTwoBears]

Thanks for the info. Looks like the catalog needs to be fixed.

 

[TahoeTwoBears]

After playing with this some more, I'd like to point out a few problems with this setup. If you look at page 8 of Jerry Work's excellent tutorial of the MFS you'll see how I initially hooked up the router bushing holder. It turns out that there doesn't appear to be a sufficient amount of force exerted by the set screw to hold it in place. The lateral forces caused by leaning way over a work piece while guiding the router put too much stress on the connection. The Festool manual shows the piece captured between both extrusions as in Brice's photo above. That method doesn't get you to the sizes claimed in the new catalog.

While the capture method works, I'd like to see a piece that was designed to be used anywhere along a length of these extrusions. If the "router block" had a tongue that had to be inserted into the extrusion from the end it would be a lot more secure and could be used for any arc or radius that could be achieved with these extrusions.

Has anyone else had more experience with this? Perhaps I'm doing something wrong that's not obvious (to me at least).

Mike

 

[CharlesWilson]

You can get a slightly larger circle if you put the pivot at the end of the 200mm extrusion. I am not sure if this will get you to 16", though.

Charles

 

[Brice Burrell]

You can get a slightly larger circle if you put the pivot at the end of the 200mm extrusion. I am not sure if this will get you to 16", though.

Charles

Charles, I hadn't considered that, good idea.

 

[TahoeTwoBears]

Thanks everyone,

I tried placing the pivot point at the farthest point. You're right, it doesn't get you to 16" and certainly not the 17" stated in the catalog. I went downtown to talk with a machinist friend this morning. Maybe I'll take the part down to him to see if he can replicate it with a tongue that would be captured (similar to the pivot point). That should make it sturdy enough that it could be used on a single extrusion without having to capture it between two extrusions.

 

[Brice Burrell]

Thanks everyone,

I tried placing the pivot point at the farthest point. You're right, it doesn't get you to 16" and certainly not the 17" stated in the catalog. I went downtown to talk with a machinist friend this morning. Maybe I'll take the part down to him to see if he can replicate it with a tongue that would be captured (similar to the pivot point). That should make it sturdy enough that it could be used on a single extrusion without having to capture it between two extrusions.

If you do have something made up please post pictures.

 

[CharlesWilson]

I have configured an MFS400 to get the larger radius, and I think that it won't have any slippage of the guide, so that a good circle should be the result. Wouldn't you know it, it is in the shape of an F!

The two 400mm sections are joined together with those little joiny thingys with the scales to the left, the top 200mm section is joined with the scale facing inward (as shown in the photo below, not outward as I originally wrote here). The second 200mm section is flipped over with the scale down and spaced from the top section to fit the guide block. The guide block is locked in place with one or more of those joiny thingys.

A close up of the guide area shows the relationship of the components.

This configuration now has a much larger radius than the 16" claimed in the catalog. Maybe they should update the catalog with the actual radius possible with this layout.

Hope this solves your problem.

Charles

 

[TahoeTwoBears]

Charles,

That's ingenious!!!!!!
I don't know if I have all of the appropriate joiners, etc. but I'll certainly get them asap. Thank you very much for putting so much thought into this. If you ever get to Lake Tahoe, let me buy you dinner.

Mike

 

[Ned]

Charles--

Looks like it should work well.  I'm glad you did the pics, too.

Ned

 

[Brice Burrell]

Charles,

That's ingenious!!!!!!
I don't know if I have all of the appropriate joiners, etc. but I'll certainly get them asap. Thank you very much for putting so much thought into this. If you ever get to Lake Tahoe, let me buy you dinner.

Mike

Mike, the standard guide rail connectors will also join the MFS profiles.

Charles, nice work, thanks for posting!

 

[TahoeTwoBears]

Thanks Brice,

I noticed that when I started back through your MFS thread. I've got those so I should be able to try this again as soon as I mill up a new table top. The only concern I have is that one of the 200mm sections has to face down. That might cause a bit of premature wear on the painted scale. I'm thinking that perhaps I might try moving the threaded connector so that I can leave it right side up. I'll see how it works.

Thanks again to everyone.

Mike

 

[greg mann]

Unless I am missing something it seems to me you could flip the setup over to the other side of the main rail to get the lettering facing up.

 

[CharlesWilson]

Unless I am missing something it seems to me you could flip the setup over to the other side of the main rail to get the lettering facing up.

That's a good thought, Greg. The guide needs to be supported by its two edges, and somehow locked in place.

You could flip the lower rail over as you suggest, and get its lettering on top. Then the guide block won't slide all the way in to the main rail, but that isn't really necessary. You would just need to lock it on both sides with the joiner inserts so it doesn't slide left / right during use.

Charles

 

[greg mann]

Glad you agree with me, Charles, but I don't see why the guide can't slide all the way up to the main rail. I will try to assemble my MFS when I get home to see if I understand your interpretation.

 

[CharlesWilson]

Glad you agree with me, Charles, but I don't see why the guide can't slide all the way up to the main rail. I will try to assemble my MFS when I get home to see if I understand your interpretation.

The threaded insert for locking the two sections together is in the way.

 

[John Langevin]

Charles,
Great idea and excellent pics (you should get thumbs up from Dan Clark a.k.a. "Picture Cop") it is so simple it plumb evaded me!