Automatic slab flattening jig?

[Kevin Jenness]

Are the individual slabs 50" wide, or are you gluing up smaller pieces to make a 50" piece? If the latter it would be easier to flatten the individual sections. CNC routers with over 48" width capacity will be harder to find.

Is there anyone in your area with a swing mill? Lucas makes a planer head for their mills, but you could probably flatten in several passes with a saw blade.

[Ronald Blue]

I hope this is visible to you for the CAMaster map.

https://www.google.com/maps/d/u/0/vi...8771278207&z=7

[Dave Sabo]

how about using the telephone or computer ?

Call or search for local shops or individuals offering slab flattening services. I've got two or three in my area.

YMMV.

[Richard Coers]

If you don't want to put in the labor, and you don't want to buy a cnc, hire the cnc time as others have mentioned. If you are good with building machines, no reason you couldn't rig up a gear motor on a belt or chain system to feed the router back and forth on rails and linear bearings and then manual jog the distance the other axis. But you'll get very close to cnc router by then.

[Steve Rozmiarek]

That Lucas swing mill attachment is a gem, that'd do the job perfectly. Bonus with that idea, it's a sawmill too. I have most of the parts to make something like that, hmmmm.

There are no slab flattening services local. Rolands Camaster lead is the best I have, and that's over 100 miles away. I live in one of the only two areas of NE that actually has federal forests. Ponderosas outnumber people here by a lot, which is nice. There are a few ash, maple, cottonwoods etc. These slabs are from an ash that didn't make it through a fire a few years back. I am gluing them up, bookmatch, to make a Y shaped tabletop. I don't have a 30" planer to process the slabs before glueup, so flattening it all in one pass after takes care of the lumps, and any joinery funny business in one function.

[Jim Becker]

Steve, in the Camheads forum site, scroll down to the Camheads Map. At the very top is a link to Google maps that you can see if there is anyone in your area.

[Tony Joyce]

Matt Cremona is working on a very large slab flattening table that uses a large motor to drive a large piece of tooling. It looks like a CNC, but is not computer controlled. Feed can be all manual or motorized on the Y (long) axis with lateral adjustments manually (and indexed) for each pass. While what he's building (from a kit) is not inexpensive, it's a whole, whole bunch less money than a CNC of anything close to the size. Matt will be keeping that unit at his warehouse because of the size. I suspect he'll have a full video of the build at some point, but he has been sharing short reels on Socials for awhile now.

https://www.blackhorsedesigns.com/clydesdale

While almost as expensive as a CNC router,
I suspect it is faster for slabs, plus the option to sand puts it a step ahead for slab processing table tops

[Jim Becker]

Agree, Tony. It's a specialized tool designed to be efficient for the job. My local hardwood supplier has a Logosol setup for flattening, but it's all manual. The Black Horse Designs setup is definitely a level above!

I mentioned Matt because he tends to go with "for purpose" solutions as he grows his business. I learned this past week from him that for his chair kits, the seats are actually not cut on CNC. Rather, his subcontractor has a machine that uses an automated blade to "scoop" out the seats. Why? It's faster for volume runs and his per-seat cost is therefore, lower.

[Kevin Jenness]

I am gluing them up, bookmatch, to make a Y shaped tabletop. I don't have a 30" planer to process the slabs before glueup, so flattening it all in one pass after takes care of the lumps, and any joinery funny business in one function.

How do you cut an accurate glue joint without flattening the parts first? I imagine that leaning over a 50" slab to guide a router sled would be difficult - narrower slabs are hard enough.

[Roger Feeley]

Have you considered setting up you fixture and hiring a high school kid to operate it.

[Steve Rozmiarek]

How do you cut an accurate glue joint without flattening the parts first? I imagine that leaning over a 50" slab to guide a router sled would be difficult - narrower slabs are hard enough.

The slabs are not bad, so I just shim them to the level I want and rip on the sliding saw and. Use wood shims so I can just rip through them, works very well. Pic is supposed to be attached, but I'm on a roll with them not posting correctly. This is the one I partially flattened. The flat part is the left of course. You can see a little color difference mid slab at the seam, it's not a bad joint, just color difference.

20220314_115232.jpg

[David Utterback]

Would the Woodmizer, etc. sawmill be able to flatten one side or even both? The one I operated could take lengths down to 48" and, IIRC, could go as low as 6/4 thickness. Shims underneath could bring the slab to the right level. The low dogs along the rails would keep it laterally table. I can envision a base built for milling a few slabs that would allow blocks and wedges to be nailed in place to stabilize underside of the piece. Do you have band sawmill nearby?

[Scott T Smith]

Here is how I do them.

Wide glue up's (42" - 52") start off as planks <25". We run these through a jointer planer to get them 95% surfaced. Then we glue them up, and send the glue up piece though the 52" wide belt sander a few times to do the final flattening and remove the glue seams.

Surfacing them to 95% or better first is critical, as we only take around .010 - .015 per pass through the WBS. If we had to remove a 1/4" of stock it would require an hour or so of sanding, but if it's only 1/32" or so it only requires a few passes.

Planks wider than 25" are placed on the Peterson swing blade mill (similar to a Lucas) for flattening - either with the saw blade or with the optional planer blade attachment). They then are glued up and go through the WBS.

Band mills are not good tools to try to flatten a slab. They don't like milling dried lumber, and if you're skimming the surface the band tends to follow the surface instead of making a precision cut.

If you have access to a planer wide enough for your individual planks, then I'd suggest planing them flat, gluing them up, and find a cabinet shop that can wide belt sand the glued up assembly. This will take much less time overall.

[Dave Roock]

Short of spending big $$$ for a solution - if you have a belt sander, put on some heavy duty grit paper & let it rip. Those 1/2" high spots could be cut down quickly, sanding seems like the best solution.

[Tom Bender]

... You could take out the major twists and humps with a power plane and winding sticks ... Maybe cut several channels with your router sled first and connect the dots...

This seems like a good approach. Then sand to finish.