Planing/Leveling Surface for Glueing

[segovia]

Hi

I have this block of Mahogany , appx 6" * 3" *3"

I want to cut it an half and joint the pieces so I have a piece 3" wide by 6" high with the end grain along the side or to put it another way 6" between the smooth sides.

I have planed both sides and used a scraper to flatten the surfaces, how flat do these surfaces have to be before gluing ?

Block shown is before the cutting in half

 

[Teckel]

Until the joint is invisible when you put them together

 

[segovia]

Until the joint is invisible when you put them together

Hi Thanks

There is a temptation to cut it now and and level after the cut but i figured it is easier to get the current (longer) surface flat before I cut it

 

[Chrispy]

I would leave it in one piece as you have done, then prepare the join with a plane only (the scraper will spoil the flat face), checking with the sole of the plane for flatness (you should be able to get it to stick to the plane by suction) only when happy with that would I cut it in half and glue up.
Looking at the picture it looks if the corners are rounded which worrys me a bit as that will spoil the joint unless you intend to remove quite a lot off the surfaces after gluing up.

 

[segovia]

I may have leaned on the corners a bit but I have a bit of tolerance in the final width so I could always trim those off. I am surprised at not using a scraper .

What size plane would you go for, I am tempted to use my small block plane or woudl you use something bigger?

John

 

[CHJ]

Remember that within reason they don't need to be flat, the two mating surfaces have to match. One can be concave the other convex or angled from a face, as long as the mating piece is complimentary.

For cosmetic reasons I'm talking small amounts but what I'm trying to instill is that you achieve as has been said by Teckel a virtually invisible join.

On something as small as 3" square holding the joining faces lightly against a well set up disc sander if you have one should be good enough.

Re: scraping, final fine finish is not always conducive to best joint, often a fine sawn or coarse abraded surface will give a better join line than one you have fine sanded or scraped as the slightly coarser fibres provide a better bond and blend line across the joint.

The joints below were prepared at 80 grit.

 

[Teckel]

I would use a block plane. Just check it with a square and make sure you can't see any light between the blade of square and your wood. Make sure its all nice and square. If you can't see light your there. Cut and glue.

 

[Tony Spear]

As long as the surface is flat, there's no need for the block to be fully sqare.
Just treat it as you would when planing two boards for an edge to edge joint.
Any out of square on the edges will self compensate when you cut it down and put the edges together.