Planing a concave form (without a compass plane)

[Dokkodo]

Is there a clever way?

I am attaching two posts to either side of an aperture for some doors to hang from, but the edges they are going on to are neither straight nor plumb, so I am hoping to adjust the posts to leave nice level parallel sides.

Both are about 7 foot tall, and go from nothing removed at the top, to about 7mm in the middle on the worst side, back down to maybe a few mm or less at the bottom, so a shallow hollow overall.

Ill probably start by sawing kerfs to the line and chiselling bulk of waste off, I suppose I could do it all carefully with a chisel but that sounds real slow and potentially tedious, id like to be left a nice flat surface and clean front edge really.

Curved bed spokeshave? Stock is about 50mm wide so might be a stretch. Maybe a block plane with the blade quite far out, this forms a sort of arc with the front and back ends of the bed, in my mind...

 

[sunnybob]

Cardboard template.
Make it in sections and then use them to draw onto the post, then cut with a jigsaw.

 

[Racers]

Axe to get rid of the bulk then a plane at an angle to clean up.

Pete

 

[Sheffield Tony]

Yes, especially if softwood, the axe and drawknife start looking like the quickest way. If you're only taking off 7mm, you need a bit if practice with the axe first I would suggest.

 

[worn thumbs]

Smoothing plane with the cap iron well back to leave the throat clear and crank the iron out to suit the shape.

 

[Doingupthehouse]

Template scribed onto thin material (hardboard, MDF, ply etc) then use a bearing guided cutter in a router to follow the pattern.

Rasps can also leave a suprisingly clean surface. Cut away the bulk by whatever means then use a half round rasp to final shape.

Simon

 

[Dokkodo]

Great thanks I will try a combination of these things. As its for indoors and wants to look as smart as possible, i might skip the axe for now, but drawknife is a good idea. Wish my bandsaw wasnt so useless(ly setup) or that might also do a good job.

 

[heimlaga]

I am with Racers. An axe is by far the best tool for the job. Possibly followed with a scrub plane used on the skew.

However this is not the perfect place to learn the use of an axe so I suggest an electric power plane. They don't plane straight and especially the shortest models can be used to plane slightly concave shapes.

 

[AndyT]

Another option which might make sense is to use a narrower post with thin strips (maybe 6mm thick) on front and back. You can plane the thick central part so it will stand central and use packing pieces behind it when fixing it vertical. With that done, you can scribe the thin facing pieces to fit exactly - they will be easy to work with a spokeshave or knife. Glue or pin them in place, fill any gaps and paint.

 

[Dokkodo]

Another good suggestion thanks Andy

Im surprised to hear that the axe weighs in so favourably for this! is that because i said 'posts' it suggests chunky external work? Maybe i should have said 'frame', for the doors I have in mind.

Im fairly adept with an axe, from carving and spoons and other bits of green woodwork, but you've also reminded me that I own a flat adze, and ive never had an excuse to do some hewing, so i might try that...

 

[Racers]

An axe is a wonderful tool capable of removing a lot or a little wood, I started to remove the waste on the outside of this box lid with an axe.

Ripple ash bog oak and brown oak box by Racers, on Flickr

Pete

 

[Dokkodo]

Great, what a lovely box. Must remember to consider my axes more in the future ccasion5: