Update:

Tried the S 75/4 FSG blade on a slightly smaller circle (37cm) on the same piece of board with a lot better results. This blade actually cut mainly square (it's about 1.5x the thickness of the S 75/2.5) and kept with the curve fairly well. My only gripe with this blade is that the cut quality isn't anywhere near "finish ready" with lots of splintering going on so once I get a replacement board I guess I'll have to use this setup for a rough cut at about 39cm and then rig my router to come in for the last 10mm and hope that it'll be enough safety zone to avoid splinters. Or should I try to tape the edge with blue tape just in case?

I guess it's off to the plywood store to get some router base jig material and figure out how I can attach a jig like this trammel thing onto my OF1400 base... And check that I have a long enough straight router bit to trim the 28mm edge in one pass (not totally sure about that even thou I do have multiple straight bit otherwise).

On a related note:

What's the point of the other gazillion Festool blades since they are too thin to stay square when in the Carvex so why isn't there a fine finish blade which is meant for cutting tight curves and be thick enough to stay square through the piece at the same time? Has anyone dared to try if the Mafell Cunex blade would fit somehow into the Carvex blade holder? 

If I read the Festool blade guide pictograms correctly then only the three different lenght S75/105/145/4 FSG blades and the S75/4 FS are for cutting squarely and only the FSG blades and the S 50/1.4 K are meant for cutting tight curves? I can understand the different blade geometries are meant for different materials like metal or plastic, but if the blades wonder to random angles sideways while cutting they are worthless in my opinion. What does the black icon mean in the S 50/1.4 K blade 'specialities' column?

Your confusion over Festool jigsaw blades is making me feel a lot less stupid!

No offence taken Peter, I haven't done this with a router before so I'm all ears for suggestions 

Reading your previous post I envisioned a strip of thin ply that has centered 5mm holes at suitable distances that are happenstance the same size as the Core jig pin  and the other end would be the shape of the OF1400 bottom and holes to attach it to the router as a "base plate". Just haven't been able to look at the routers base plate to see how it is screwed/attached to the router. I'm expecting to then be able to run the full circle with the router effectively at the 'end of a rod' so to speak.

I'm mostly unsure how to keep the piece in place since can't really clamp it from the sides with the clamping element nor putting a clamp in the middle is going to work much better since I'm routing all around it. Wonder could the routing be done in multiple segments of the circumference without too bad burning/misalignment and rotate the board one segment at a time?

The only solution that I've come up with the possibility to doing continuous circle is some sort of a stand that's clamped to the table and has something similar material on it like the anti-slip rubber of the guide rails or some sort of a vacuum clamp. Unfortunately I don't have a vacuum clamping system nor the materials to build such a anti-slip stand either.

Another question about using a router for this sort of edge trimming is that should I use a straight bit or a spiral cutting bit (up or down)? Does it make a big difference in the finish quality?

Reiska

Toms last post is good advice but make sure that the tape is doing the job before you find out the hard way.

As you are trying to make a hole for a round sink - might there be a lip to the edge of the sink to hide the few mm near the hole? That would give you some wiggle room.

You could use the piece of wood that you have ruined as a base piece.

Fix the new piece of wood to your base piece. At the centre (of the sink) make a hole all the way through your new piece into the base piece - that way when you come to the end of your circle the trammel is still fixed at the centre (of the base piece).

Cut the hole using your trammel taking care at the very end when the plug in your new piece is free to move if the double sided tape has failed.

You could use some thin nails through your nice piece of wood (at the edges and in the centre) into the base piece and fill the holes later.

Spiral bit is good. Do the cut in stages if your meet too much resistance.

Peter

You have a Carvex?


Tom

 

Circle

lol No joke you can only see a 35-40% of it in the video  







JMB

Thanks JMB - that's pretty much what I was planning on doing based on what Peter wrote above. 

Peter: Just to correct a slight misunderstanding in a previous message of yours - I'm not making a hole in the table top for a sink but a cover to the existing sing that's in the camper van. The sink has an internal lip where the cover will seat (top inside diameter 38cm and lower parts inside diameter 35,7cm). When the cover is in place it will double as a cutting board/table surface next to the gas hobs.

I was looking at my router tonight after work and there are two screw holes (M6?) in the bottom of the OF1400 baseplate - could these be used for the attachment of the plywood trammel since the 1400 doesn't have the conveniently detachable baseplate of the 2.2k?

yeah it is dude! Brilliant! Love it  makes me actually want to use the CMS with out the detachable base I wouldnt bother with the CMS just pain in the arse.  I hardly used it before but now I use it loads more.  I think sometimes festool dont try and make stuff site friendly even though its suppose to be portable but dont know about you but I dont like carrying a box full of bits and pieces which take 5-10 mins to screw together to then be taken apart and most likely loose something on a job.

JMB

I imagine that the OF1400 base plate is like that - I made up my trammel by screwing my trammel are to the base of my OF2200. I think that JMB's solution, with the spare base mounted on the trammel, is brilliant and an excellent way to go if you expect to do more than one.

It is interesting, we have a round top to the sink in our motorhome. On the underside it has plastic so that it can be used as a chopping board.

Peter

Dean - I did the 49mm hole for this clock that way...

Peter

Oops - no I did it this way - I think!

Peter

"When our engineers sit down to design a new tool, they don't aim for mediocrity. Only the finest engineering, design, components and finish result in a tool worthy of the Festool name."

Must be talking about the Carvex.  Was working for some Germans on their holiday home here in France today and he saw me getting angry.  When I explained it was the Carvex, again and that I'd left my Bosch in the workshop he said "Yes we make rubbish in Germany sometimes too."

very nice reiska. much better than using a jigsaw

Yes, I just originally thought that I could do a perfect circle with the jigsaw and then do the rebate with a bearing router bit...

This way done the making of the whole lid including sanding & finishing took about ½ of the time to do the jig