A buddy wants me to help make a small live edge bar top. My local dealer made me a good deal on a small (60”) slab of big leaf maple. But it needs some flattening.

Not one that owns a CNC machine, I’m going to have to make a sled to do it. I’ve watched the videos on it and have seen everything from the plywood or melamine box and rails, to metal linear rails with bearings, up to the kits like the Woodpeckers one.

Just curious to hear from people who have done it, pitfalls to avoid, and ways to make it as idiot-proof as possible.

I have done it with walnut. Turned out that after I completed the sled it was a really simple task. Make sure your workpiece is secure with no possible movement. I used cams and double sided tape that worked well. Use the flattest side as the base first helped to keep it in one place. I used a Bosch router with a 1 1/2” flattening bit and that worked well. I have seen it done using an electric hand planer that I will try someday. Good luck, woodworking is a great pastime.

flattened a 3 1/2 ft x 7 ft sugar maple work bench. Used 1 x 3 80/20 for the guide rails over the length and 1 x 3 80/20 with a 1/4 aluminum strip screwed to the bottom for the cross piece that the router rode in.
I used a 7/8 router bit for the cutter. Each pass was up to 1/8 deep.
Clamped the 80/20 to the side aprons of the work bench.
Had to make sure that both rails were parallel before starting.


some of the issues I had was all the chips/sawdust can pile up in spots and cause issues. Had to blow off after every pass to avoid this.

I had to flatten a glued up white oak "slab"

I used 2x 2x6 and 3x 2x4. Very simple jig and I got the "slab" flatten to just over 1/32 over a 6' run.

I appreciate the input. I've got a line on a free metal bedframe that I'm going to use the steel side rails as the sled rails for the flattening jig. Just have to square up some side rail material.

I do have one question concerning order of operation. My thinking is that I would flatten the bottom of the slab so I have an level surface, then I would do any resin pouring in the voids on the top side, and then flatten the top. And after it's all flat, do the bow ties in a couple of cracks that I'll have to tend to. Is that correct?

I've done it with a sled that I built.  It isn't that bad to accomplish. Gonna be honest. . . You will invest waaaaayyy more time building the sled than you will actually flattening.  Take your time and get it right the first time. You don't want to waste that gorgeous slab.

You'll need a fairly flat bottom so that the resin flows to level with the bottom. It doesn't need to be perfectly smooth; generally level should be good enough.  If it isn't flat on the bottom then you'll waste resin on the top and spend extra time removing the extra.

I think your work plan is the right approach.

A thickness sander is what you really want. Maybe a local cabinet shop?

Wish I had access to one, but I don’t. That’s why I’m making a router sled to take care of the flattening and removing the excess resin on the top after the pour.

It'll work.  A belt sander will be really handy if you have access to one of those.  Might even be worth it to pick up the $50 Harbor Freight model, even if you never use it for anything but this.

Got a belt sander already so I’ll keep that in mind as another tool in the arsenal.

Would you consider using the belt sander or angle grinder with a flapper disk to remove a bulk of the resin before flattening the top with the router sled?

I'd probably opt for the belt sander, just to keep things as flat and level as possible.  Clogs up the belts pretty bad, so get some chunky ones for the first passes.  I'd definitely use the router sled for as much of the removal as you can though.

Depending on how the slab was dried, or if air dried how long it dried and what the moisture content got down to, it can still move as stresses are relieved from taking off only one surface
I would let it set a few days if you only cut one face and see if it moves or twists.
If you don’t want to resurface or do both then wedge up any where on the sides that it’s no longer flat so it doesn’t  wobble when you do the top face
If it’s still wet - like over 15% - I would put it back and go work on your flattening mill and maybe 8-12 months later come back to it. One year for an inch thick board is a good rule of thumb, but as the board goes up in thickness the drying rate is not linear.

And I would do resin cleanup with the flattening mill.   Why fill up the shop with tons of fine dust?   If you had something like a timesaver that might be Ok and a bunch of expensive belts.   But the flattening mill is going to be more precise and give you a flat surface installers of something wavy with dips and pockets - because the wood and the design aren’t the same hardness.

I wouldn't.  Just hit it with the router.  Your previous order of operation is how I do it.

Another suggestion.

If there is a sawmill, BAND type near you the slab can be flattened on the mill. I've done it for a local wood worker. I took the slab and placed it on the mill bed with the high side up. Found the lowest spot and set the blade 1/16 in below that. Then very slowly sawed the board flat. Flipped the slab and repeated the process. With a band saw style mill you have to saw VERY slowly when doing this to prevent the blade from deflecting. It also leaves a smoother surface.

EBR

I work in a commercial woodshop/mill for a living.

Is it a solid slab or a glue up? Either way there are lots of specifics that will determine your outcome.

Best bet would be to take it to a shop that has a large commercial/ industrial sander.

Would be best if one side is already flat but they could do it either way.

You might want to ask your 'employer' about that FIRST skippy...


Most shops are going to be really, really hesitant to stick random stuff from random people that walk in out of nowhere through their machines. Those belts cost money (not to mention the other parts that could be trashed instantly by a single hidden nail or stone or whatever...) and potential machine 'downtime' for repairs can be a major problem (think COSTLY) for many places that depend on them.

If its narrow enough to fit through a planer, then that'd be my first guess.  Make a jig/sled for it so the board doesnt rock or bow as it goes through.  Some jointers and drum sanders are open on one side, allowing you to pass the workpeice through, rotate it 180, and pass it through again.  That lets them handle something twice as wide as they normally would.

After you have used the jig/sled to flatten one side, simply flip the workpiece upside down and feed it through without the jig to true up the other side.



I have a shapeoko pro XXL.  It supports roughly 40" width and infinite length.  You could use one of those, then move the work piece and run it again.  Doing it in whatever sized section the CNC had.

I have also used jigs like you've asked about.  The results will only be as good as the jig you come up with.  By the time you buy long rails and mount them together with some wheels and then come up with a bridge that will hold the router and roll back and forth, you may as well have just ordered a cheap CNC.  I assume for your purposes, you dont even need a great CNC, as you will probably be sanding it by hand afterwards.

OP, how wide is your slab?