hi, i'm andrew with infinity cuttingtools. as woodworkers we all have a desire to work with large pieces ofmaterial like this live-edge slab to make furniture like this coffee tablethat i recently finished. today i'm going to show you how i go about flatteningthis slab using nothing more than a homemade planing sled, a triton three and a quarter horse plunge router, and an
router woodworking how to, infinity tools mega dado and planer router bit. to flatten a slab we need two maincomponents. first of all we need the planing sledand we need a good router. the sled itself is simply a couple of boxes.
the first is a box that surrounds theslab and provides a set of rails that are a flat surface. the sled bridge holds the router andallows it to travel back and forth across the slab and it references off ofthe sled box. once we have our sled built we can put our slab inside of it, level it up (i'll show you how to do thatin just a minute), and go about flattening our slab. the sled itself is very simpleconstruction. i simply made it from mdf. this is three-quarter inch mdf and itactually only took me one sheet for my slab.
i used pocket screws and a kreg k4 pocket screw system to build thesled makes it very quick and easy to build. and when i'm all done i can use the mdf for other jigs,fixtures, or projects because i don't flatten slabs on a regular basis. probably the most important part of thisentire project is a good router. i'm going to be using my triton threeand a quarter horse plunge router with an infinity mega dado and planer router bit. ialso have an infinity large router base
plate so that my router stays nice andsecure and is supported in my planing bridge. the final piece of the puzzle is arouter collet extension. because i have to reach through the base plate andthrough three quarters of an inch of mdf of my planing bridge just to get to myslab, i'm going to need a little extra depthof cut. that's where the router collet extension comes into play so i can reachnice and deep and get to my slab once i've planed off the high spots with everything assembled we can goabout flattening our slab. the way
everything works together is the boxsurrounds the slab. the bridge sits over top of it and the router slides withinthe bridge and see i'll simply pass the router all the wayacross and back. one key thing that i've done is drawlines on one edge of my sled box. these lines are in one inch increments and they're going to allow me to index the sled bridge down the slab every time i make a pass. i have a pairof simple spring clamps to help hold my sled bridge in place so it doesn't movearound while i'm making my cuts. because almost no slab that you'll find will beperfectly flat (if it was we wouldn't
need to flatten it), we're going to have to do some shimminginside of our planning sled to make sure that we remove the least amount ofmaterial possible from our slab. to do this, i actually start with pieces of mdf.they're nice and consistent in thickness and i could use some as shims at thecorners of my slab. you can see i've got one shim under this corner and actually twoshims under this corner. the reason for that is the slab hasabout three quarters of an inch of twist over its length.
my goal here is to make sure that my lowcorners match each other and my high corners match each other. to check myprogress i simply use a ruler and the planing bridge as my guide. i measurefrom the bottom of the planing bridge to the top of the slab. i got lucky today and i only neededpieces of three quarter inch mdf to do my shimming. if i wanted to fine-tunethis more i could use just a regular wedge-style shim in between the slab andthe planing sled. you may also notice that i have a stripof mdf inside my planing box. this strip is loose within the
box and it goes from one edge of the boxto the other. this is my base shim and it ensures that the entire slab cannotslide back and forth inside the planing box while i'm routing. the final piece iwant to add is to capture my slab - to keep it from sliding back and forth - and all ido is take another piece of mdf, put it on top of my stack so that it pushesagainst the edge of my slab, screw it down, and now my slab cannot move. before i get started i want to talk a little bit about the router bit speed and depthof cut that i'm going to be using. i found that in red eucalyptus, which is apretty hard and tough wood, that the router and the bit liketo run at a speed around sixteen
thousand rpm. this is roughly midway between top speed and low speed on a variable-speed router. i'm actually set right at three on thetriton router with a scale of 1 to 5. i'm also going to be taking passes ofabout 1 inch wide. this is a 2-inch diameter bit and ifound that that one inch wide path is perfect because it eliminates any climbcutting issues. i'm always going to be making a push cut with the router bit.i'm also going to be making my cuts about one-eighth of an inch deep. i may start a little bit deeper at three sixteenthsat the very beginning because i'm only
going to be removing a few high spots.but once i start removing any bulk of material i'm going to reduce my depth of cut toabout an eighth of an inch per pass. i've got the first side of our slabcompletely flat. now i'm ready to flip the slab over re-shim and get to workon the other side. i've got my slab flipped over repositioned and i went ahead and re-shimmed the slab. this time, because the bottom of my slab is flat, i'm using the same number of shims under each corner.
this ensures that the bottom of the slabis parallel with the top of my sled box and i should get a nice consistentthickness slab. and now i can go ahead start cutting at the high spots, work myway down just as i did with the first side, and end up with a nice smooth flatslab. i just want to take a minute before igot all cleaned up to show you or explain why i decided to wear arespirator-type mask versus a regular paper mask. while a paper mask would probably havebeen just fine for the size of particles of sawdust that i was creating, i findthat the respirator-type mask is more
comfortable to wear for extended periodsof time. i actually can breathe a little more freely when i'm wearing this maskand i get a better seal all the way around my mouth and nose when i'mwearing this type of mask. here's our finished product. the slab isnice and flat ready to be cut the size and sanded. be sure to subscribe to our youtubechannel as we take this slab and turn it into a shaker-inspired table. also, be sure to check out our blog formore information on flattening a slab as well as all the other projects and toolsthat we use here in the infinity tool
shop. be sure to check out our facebookpage and give us a "like" so you can stay up to date on the latestthat's going on here at infinity.
