Flattening a 3m x 500mm board

[Helvetica]

Due to planer snipe worse than I thought, I’m having trouble flattening a large sideboard top. Basically one substantial corner is around 2mm lower than the rest (36mm thick overall). It’s no big deal but I’d love some opinions on which method to use:

Jack plane by hand, or router with a milling bit.

The only reason I’m thinking of the router as an option is, I just used it to flatten my bench. I made a sled, and fixed a length of ply on the sides levelled with a spirit level, and went across the whole bench. The result was impressive.

Any preferences?



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[MikeG.]

If you use the router you'll need to use a plane afterwards to clean it up. For me, therefore, it seems obvious to use a plane for the whole job. Don't forget your winding sticks!

 

[Simon_M]

I did something similar except I made a flat bench top using a router and sled, and then used a pair of arcs to also make space for two “seats” (bums on seats).

I found it was easier to run the router along the table on the “up” strike, to run it back on the “down” stroke half a width over (like having a 2nd pass but quicker) and much better than going across as is usual.

I also found it easy to use my workbench as a reference surface. Can cut two slides e.g. softwood and glue them to the sides as rails. They should be sufficient to raise the workpiece up.

The workbench supports the rails and “stops” on the sled stops the router cutting off the rails completely. So it’s your workbench that sets the flatness so the rails should be flexible enough for the workpiece to be against it e.g. might need to use a clamp or two to pull workpiece onto the workbench.

It’s necessary to sacrifice 1/2 the side of part of the rail because you want all the workpiece flattened - seems a good trade off. I’ve also used chipboard as rails because no strength is required. I cut the rails off on the table saw (glued to workpiece so no screw holes to patch) and then later, a cross sled to cut the oversized ends to square.

I have used it for a 2nd workbench, a bench - seems to work. The router bit wasn’t particularly wide and the finish sufficiently good to require only a quick sand with 120g and 240g with an random orbital sander. The up/down routine helps with the finish.

FWIW I routed both sides, also sanded with the grain and put the same finish on the unseen side too. The top was screwed in middle at each end and outside held down with cleats to allow for any movement.

Someone will suggest that sighting boards and a jack plane will work as well or better but using the router method (for me) is foolproof and is quick.

There is also a method using crossed thread to setup parallel rails. These rails need to be exceptionally flat and not move and you need at least one level across one end. Using the workbench as a level avoids the need to keep the rails (self) level - otherwise with thread it could also be 2-3mm down in one corner...

 

[custard]

A large part of my business is making waney edged dining tables and desks. The slabs I use are generally too big to pass through my 610mm wide planer. Consequently I do most of my flattening with a traditional wooden jack, and that also holds true for super hard tropical slabs and slabs that are too big for one man to lift. Once you get into it this way of work it's astonishing just how efficient a wooden jack plane can be.

 

[Fitzroy]

If you have 2mm of snipe on one end and the rest is flat could you not build that area up by glueing on a piece then flatten locally?

 

[Rorschach]

Was it your planer that caused it?

If you, attach some sacrificial pieces to each end, longer than the snipe area that occurs, then run them through the planer again.

 

[topchippytom]

If you have 2mm of snipe on one end and the rest is flat could you not build that area up by glueing on a piece then flatten locally?

That would spoil the whole look of it.

 

[Helvetica]

Was it your planer that caused it?

If you, attach some sacrificial pieces to each end, longer than the snipe area that occurs, then run them through the planer again.

I’ll try that. It’s killing me. Brand new HSS blades, set to drag 4-5mm and I only trust it to roughly thickness


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[Benchwayze]

Was it your planer that caused it?

If you, attach some sacrificial pieces to each end, longer than the snipe area that occurs, then run them through the planer again.

Secure the work pieces to a longer MDF piece with hot melt glue as a datum point to do this. It does work.

My Sedgwick thicknesser is reliable, but I always thickness a piece of scrap to make sure I get the right setting.

John (hammer)

 

[Helvetica]

I went with the router method - thanks Simon for the detailed guide - it worked really well. An awful lot of sawdust was created as I couldn’t fit dust extraction with the depth of the cutter! Finished with my record #7 and a super fine cut. I’ll sand after assembly. I may well try by hand next time, after I get my hands on winding sticks. Cheers lads


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