flattening a slab what router bit??

[Robbo3]

I flattened a large tree slice using a sharpened 25mm flute bit. Do the 6 wing jobbies just make the job quicker (larger diameter) or do they leave a better finish as well? With the 25mm flute bit I wasn't really restricted for depth of cut- it'd quite happily remove 15mm high spots. Are the 6 wing cutters limited for depth ?
I've got some large slabs that would need router sledding.It'd be interesting to hear the pro's over a normal straight flute bit.

Mine was a one off, though there may be one or two more in the offing, & was jigged with whatever I had available. The side supports were taken from pallets & the sled was just a length of melamine faced chipboard.
I would think that wide bits add more complications especially with two non parallel irregular surfaces.

 

[memzey]

A slightly sweatier option I know but is there a reason why you don’t want to do this with bench planes? All in all once you factor in the time it takes to make the jig etc. it’s probably much quicker and far less likely to ruin your slab.

 

[Eric The Viking]

Wowsers, so what's the appeal with them then ? It can't be speed if you're limited to 1-2mm per pass.....I'm genuinely intrigued now.

The 6-wing one, certainly, probably won't do what you want. I got mine because it would let me get to a pretty good surface taking off an absolute minimum of material. It's not really the weapon of choice if you've got 1/2" depth to deal with.

#1: Clean cut as mentioned. I think both the 6-wing and 3-wing cutters have rounded corners, so they don't rip up the grain.

#2: Bigger diameter - the cutting edge is moving faster (so the router itself doesn't need to scream) - in theory although the cut itself is shallow, you can work it over the surface more quickly, and because it does less damage, get more from your slab. I'm sure it's faster. The depth may be less, but each "wipe" across the board can be about 30mm wide. And I have taken 2-3mm at that depth, although that is probably the max for my T11 in a sled (need to improve my sled though as it's a glorified trammel arrangement at the moment). The issues seem to be getting the router exactly perpendicular to the plane of cut and making sure it doesn't bounce - because the cutter is wider, it "amplifies" any alignment issues. It's capable of an exceptionally clean finish, but only if it is exactly parallel to the plane of movement and rigidly held in the vertical axis.

As well as flattening big surfaces I use mine in the router table for things like micro-tuning tenon cheeks (oh, the shame of it! ), and making similar small dimensional changes. For that, with a mitre fence, it's a cheeky* but neat solution - I can easily dial-in 0.1mm adjustment.

Again though, it's not something you're likely to need to do very often!