Making a Cello #8: Flattening the Rib Assembly

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Blog entry by PhiltheLuthier posted 11-15-2012 09:42 PM 2920 reads 0 times favorited 1 comment Add to Favorites Watch
« Part 7: Linings Part 8 of Making a Cello series Part 9: Corners and fixing a joint! »

Before the major work of today there was some minor repair to do. One of the joints between a C rib and lining was not up to snuff.

Exhibit A:

To fix this I soaked some paper towel in water and laid it on the offensive joint in order to soften the glue. After a long while soaking I squeezed it a few time with my fingers to get it moving, then clamped it up again; the result being something much more acceptable.

Once dry the flattening begins. First with a block plane to bring the linings flush to the ribs.

In reality this is the way one would normally flatten the whole assemble, but since I’m trying to save time (because time is money… or I’m lazy…) I used sand paper!

80 grit self sticking paper on an ostensibly flat surface:

I colored the whole thing with pencil to see if I got everything, and started sliding the the thing over the sandpaper. Back side of course, since I’ve not lined the top side yet.

Corner detail after some sanding:

About 20-30 minutes later maybe not even, no more black, the whole thing is flat!

By plane this would be at least a 2 hour job, and require sharpening once, maybe twice due to the glue and end grain.

Now for the excitement I promised last time! Before putting in the linings on the top side I have to trim the excess rib and block height. So I set the assembly on my flat table and lined things up… turned on the laser, a little burning and the thing is trimmed!

Okay, okay, the laser was to help me draw the tapered line between the top and the bottom block (as you may recall they are different heights), but frankly it was impossible to line up correctly as any minuscule movement at the laser was huge at the rib assembly. So that plan was scrapped to be replaced by…

Two adjustable feet attached to the mold!

So I leveled the assembly so the top block was the same height as the bottom, then drilled a tapered hole in a block of wood to hold my pencil.

Checking the pencil height:

Then I drew a straight line around the whole thing.


After this I break out the oscillating saw, and zip around to cut off the excess.

Blurry action shot:

All done:

I mostly used the round blade, because it has nice little teeth with very little kerf, but switched to the plunge blade to get through the top block.

And now the assembly is ready for linings on this side, I’ve made the mortises, just have to bend and fit the linings, then another sand paper session, and oh so much more!

1 comment so far

View SPalm's profile


5326 posts in 4123 days

#1 posted 11-16-2012 12:00 AM

Hey Phil,
I am enjoying the heck out of these blog posts.

And no, I did not fall for the burning laser technique :)

-- -- I'm no rocket surgeon

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