Re-Saw day

Timbuck

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The weather today is not very good here in the North East..rain, snow , sleet, etc: but I managed to saw a few slices ready for later in the year when the sun returns. :)
AD36C620-FDD4-447F-A800-6B41ABC7603B by Ken Timms, on Flickr
 
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The piece on the right appears flat sawn to me. Is there a concern that it is not quarter sawn? My understanding is that you want quarter sawn pieces to lessen the movement caused by humidity variations.
 
Perhaps I’ve miscounted but that looks like about fifteen sets to me and another fifteen Timms Sopranos is good news for the Uke playing community. I suspect that there’ll be a lot of happy customers by the Summer, I wish the successful bidders hours of joy with their Timms ... and maybe, too, that I win the lottery so that one of them could be mine :drool: .
 
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I try and resaw them at 3/16” then sand them down to .075” for the backs and sides..and the tops at .065” ish depending on the flexibility.

Thanks! So they're a little over twice their final thickness for back and sides. I haven't resawed parts before (I didn't have the bandsaw to do it, but I just got one and I'm now working to get everything set up right and have acquired a suitable blade). I had been contemplating aiming to cut them a little thinner than you are, but maybe that's not a good idea? I'll be starting with cherry and red maple, most likely. I don't have a drum sander, so I will likely be hand planing to final thickness for the time being.
 
I haven't resawed parts before (I didn't have the bandsaw to do it, but I just got one and I'm now working to get everything set up right and have acquired a suitable blade).
It's the set up that counts keep the base of the billet square to the fence and dont apply too much side pressure co's thats what wears the side of the blade and causes drift...It can be dissapointing when you think you've sawn a nice even slice and it ends up 4mm thick at the top and and only 1mm at the bottom :( ...Or even worse if you get cupping
..some guys even sand or plane the billet flat on the face side after each pass...But I found that to be wasteful.
There are many other different techniques for sawing veneers with or without the fence....find one that suits you.
 
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I'm glad you post stuff like this Ken. Too much store is placed in the 'quartersawn' paradigm. It is roundly ignored when people want a 'quilted' or 'birdseye' figure in maple. And FYI - most BR these days is either flat sawn or rift sawn. What say ye all then?

Side Bar: It's 46 years since I studied it but a recall that quartersawn oak moves 0.125" across a width dimension of 12". Maybe someone can fact check me on this because I cannot remember the value for flat sawn and am too tired to Google it. A little bit of technical knowledge more qualified than mine would certainly further inform this discussion.
 
I'm glad you post stuff like this Ken. Too much store is placed in the 'quartersawn' paradigm. It is roundly ignored when people want a 'quilted' or 'birdseye' figure in maple. And FYI - most BR these days is either flat sawn or rift sawn. What say ye all then?

Side Bar: It's 46 years since I studied it but a recall that quartersawn oak moves 0.125" across a width dimension of 12". Maybe someone can fact check me on this because I cannot remember the value for flat sawn and am too tired to Google it. A little bit of technical knowledge more qualified than mine would certainly further inform this discussion.

The answer strongly depends on the seasonal change in moisture content. If the wooden object lives in a typical climate-controlled space year round, sources say to figure on a 3% net change (this being the wood's change in moisture content, not the change of R.H. in the environment). For white oak, the 10" quartersawn board would move 0.054" (a little under 1/16th), and the flatsawn board would move about twice as much, 0.11" (a little under 1/8th). If the wood is not in a climate controlled space, you could hit 1/8th" movement for the quartersawn board.

I suppose it's good to climate control your shop to 40 - 50% R.H., and that way your project starts out in the middle of its width range. Then it can probably survive pretty big swings in humidity because it will only vary, say, +/- 1/16th instead of gaining or losing a whole 1/8th.

I got these calculations by referring to a Popular Woodworking article that turned up from a Google search. Probably other sources would yield differing answers.
 
Many moons ago, when I was deeply interested in traditional hand-powered woodworking, and wanted nothing to do with modern gadgets or electricity, I had made a "shop humidity gauge" out of a cross cut of a wide flatsawn board with one end screwed to a steel bar. The bar had markings for 30, 40, 50% etc at the points that matched the wood's dimension for the given humidity. It provided a good reference point for how much slack to leave in joinery for things like wide breadboard ends on a table top - which was very helpful, since the shop I used then was not climate controlled at all and would seasonally swing quite a bit.

You can look up the expansion rates for specific species on wood-database.com - it lists radial (quartersawn) and tangential (flatsawn) rates per species. 3% net change in moisture content in a climate controlled space sounds like a lot to me, but I guess it depends on what you mean by "climate controlled." This page has a graph at the bottom showing the moisture content your wood will have at equillibrium for a given temperature and humidity:

https://www.woodproducts.fi/content/moisture-properties-wood

Using that reference and the data on wood-finder you can figure exactly what the change will be.

Personally, I don't specifically look for flatsawn or quartersawn, but rather just the quality and appearance of the specific board. We want our instruments to be durable to humidity changes, but IME that comes just as much if not more from the design and construction than just the wood being sawn a certain way. For instance - radiusing a back or top gives it compliance where it can respond to dimensional changes safely (by pushing the curve bigger or smaller) instead of being forced to split itself apart, like a flat back can. When I started building, I purposefully jacked my shop to 70% humidity for a few days, then made a pair of test backs - one flat, one dished - and put them in front of a fan in my garage, where the humidity was around 20%. Surely enough, the flat back had split a few weeks later, and the dished back just deformed.
 
Many moons ago, when I was deeply interested in traditional hand-powered woodworking, and wanted nothing to do with modern gadgets or electricity, I had made a "shop humidity gauge" out of a cross cut of a wide flatsawn board with one end screwed to a steel bar. The bar had markings for 30, 40, 50% etc at the points that matched the wood's dimension for the given humidity. It provided a good reference point for how much slack to leave in joinery for things like wide breadboard ends on a table top - which was very helpful, since the shop I used then was not climate controlled at all and would seasonally swing quite a bit.

You can look up the expansion rates for specific species on wood-database.com - it lists radial (quartersawn) and tangential (flatsawn) rates per species. 3% net change in moisture content in a climate controlled space sounds like a lot to me, but I guess it depends on what you mean by "climate controlled." This page has a graph at the bottom showing the moisture content your wood will have at equillibrium for a given temperature and humidity:

https://www.woodproducts.fi/content/moisture-properties-wood

Using that reference and the data on wood-finder you can figure exactly what the change will be.

Personally, I don't specifically look for flatsawn or quartersawn, but rather just the quality and appearance of the specific board. We want our instruments to be durable to humidity changes, but IME that comes just as much if not more from the design and construction than just the wood being sawn a certain way. For instance - radiusing a back or top gives it compliance where it can respond to dimensional changes safely (by pushing the curve bigger or smaller) instead of being forced to split itself apart, like a flat back can. When I started building, I purposefully jacked my shop to 70% humidity for a few days, then made a pair of test backs - one flat, one dished - and put them in front of a fan in my garage, where the humidity was around 20%. Surely enough, the flat back had split a few weeks later, and the dished back just deformed.

Thanks. Hearing about your experiences and experiments is helpful.

When I did a google search, multiple sites recommended using a 3 or 4 percent wood moisture swing for the wood movement calculations in "climate controlled" environments. What "climate control" really means in terms of R.H. wasn't necessarily explained, so I'm not vouching for 3% being the "best" assumption to plug in. In real life, it's normal for many stringed instruments to experience pretty wide humidity swings, so it's probably wise to account for wood movement in instrument construction. Radiused backs and fronts probably help a lot. Have you looked at whether traditional ukulele bodies seasonally expand and contract slightly across their width in response to changes in front and back width?
 
Looks to me like the image is 'washed out'. Some SA mahogany is quite pale when fresh sawn but it oxidises soon enough.
 
Looks to me like the image is 'washed out'. Some SA mahogany is quite pale when fresh sawn but it oxidises soon enough.
 
It’s interesting (well to me it is) to see just how much difference in appearance a finish makes. Look into the sound hole and then look onto the soundboard, same wood but completely different appearance. As far as I understand it the finish used isn’t any form of particular die but rather something that protects the wood and somehow interacts with it to alter how it reflects light. H’mm, not my best explanation. I rarely see him now but someone I know works with wood, it’s a hobby for him. That person applies wax to finished products and it completely changes surface appearance, allowing the beauty of the wood to be visible and shine through.
 
Think of the difference in appearance of snow and ice - a finished piece of wood is like ice, it's a somewhat uniform surface for light to interact with. Whereas unfinished wood is more like snow, there's a highly irregular surface between the air and the wood.

Plus of course, most of the finishes we use have a degree of amber tint to them, naturally, even if they're not deliberately colored.
 
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