Offerman Slab Flattening Jig

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Project by justgrif posted 02-22-2016 10:42 PM 2660 views 21 times favorited 4 comments Add to Favorites Watch

Since I plan on making several more live edge tables, I decided to build Nick Offerman’s jig as featured in Fine Woodworking Magazine. It took me a weekend to source my materials and put everything together. Luckily, I live near Highland Woodworking, with a Home Depot and Lowes practically down the street.

The bulk of the router trough is made of 3/4” MDF. The bottom is melamine-veneered particle board. The rails and supports are pine 2 X 6’s handplaned to equal size and square. I made a phenolic router plate that custom fits to the trough so the router can slide back and forth with zero wiggle. I’m using a 1.5” wide plunge cutting router bit because that’s what I had on hand, though I may see about getting something even larger. Everything is fastened together with plenty of countersunk 2.5” Spax screws.

Something I especially like about this design are the vent holes in the trough, allowing the router plate to sweep dust out of the way as it moves. This is basically a 48” wide planer, so you can imagine the amount of waste this potentially generates. I may cut a few more holes along the middle area.

The jig turned out really solid and operates well. It’s a tight fit in my tiny shop, but will break down and stack on a high shelf in the rafters pretty neatly. I may make some of my own tweaks, such as adding dust collection and perhaps tape some gradations to the sides so I can dial in the rough height quickly. I’m sure this contraption will seem comically large when flattening cutting boards. I’m also somewhat curious about how it would do on glued-up panels too wide for my planer.

4 comments so far

View pottz's profile


767 posts in 403 days

#1 posted 02-22-2016 11:16 PM

i gotta make one of these ive done quite a few slab tables and have always used a power planer and long level to flatten the tops this would sure make that job a lot easier thanks for reminding me of this jig.

-- sawdust the bigger the pile the bigger my smile-larry,so cal.

View SteveMI's profile (online now)


943 posts in 2713 days

#2 posted 02-23-2016 02:44 PM

I know a guy with some slabs and have heard his problems in getting them flat when too wide for a saw mill or CNC table. It seems they are always 2-3” wider than he can handle. Of course, maybe that is how he came to have them.

Only problem with bigger diameter bits is that you either have to slow down your travel speed or really increase the router horsepower.


View ChrisK's profile


1794 posts in 2500 days

#3 posted 02-23-2016 02:48 PM

Nice work. I need to go browse Highland Woodworking again. I have not been down there in about 5 years. Bought my 6” Jet joiner there 12 years ago. Used it make the crib both my boys used.

-- Chris K

View BikerDad's profile


284 posts in 3020 days

#4 posted 03-08-2016 12:26 AM

Depending on how smoothly the router slides in it’s box, you may want to add UHMW strips to the bottom of the router “plate” and the sides of the plate.

-- I'm happier than a tornado in a trailer park! Grace & Peace.

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