Rough Lumber Milling Expectations

[pkinneb]

When milling rough lumber what should I expect for finished thickness on 4/4, 5/4, 8/4 etc? If you plan on book matching an 8/4 board what would your final thickness expectation be? I'm trying to determine if I am being to optimistic or if there is an issue with the lumber I am purchasing. I would have thought I could get 2 - 3/4" boards out of an 8/4 rough lumber but I am only seeing about 11/16" on a pretty regular basis. 

[Coop]

Only going from recent experience on some 3 year, self dried 8/4 slabs, I thought the same. I find myself almost crying after resawing these things. Before resawing, the winding boards were very encouraging, but they sure took a turn for the worse after running them thru the bandsaw. It's a bitch watching that much walnut go to the curb for pickup. 

[Sawdustdad]

It requires great accuracy to turn an 8/4 board into a pair of finished 3/4 inch boards. If you are getting a pair of 11/16 boards when finished, you are doing pretty well.  The main issue is an inaccurate resawing process where there is enough variation in thickness of the pair of boards that you can't get both boards planed smooth at the 3/4 dimension. 

Some tips. 

1. mill the 8/4 board straight, S4S

2. Strive for perfect resaw accuracy, even if you have to go to the table saw for part of the effort or by ripping from both edges. 

3. accept that the final product might not quite make 3/4. allow for this in your design. Usually, bookmatched panels go in doors, so you really don't need 3/4 inch there. 5/8 or even 1/2 is usually fine. 

If I needed 3/4 inch bookmatched panels, I'd start with thicker lumber, 10/4 or 12/4 and be left with a third board at less than 3/4 for some other project. Or I'd veneer the panel.  I can't think of a time when I needed 3/4 inch book matched lumber, but I guess a table top might be one case. I've veneered such situations.  

 

 

[Eric.]

Depends on the size of the piece it's going in.  Often a piece doesn't require a full 3/4" and I agree with SDD that usually a bookmatch will be going in doors anyway.  Your maximum yield will mainly be determined by how much movement you get in your board after you resaw it.  If you had an absolutely stable board that didn't move at all, it's possible to yield two 7/8" boards out of a fat rough plank.  But that's not reality most of the time.  Boards don't like being resawed...it's extremely stressful.

Finished thickness should be determined by the scale of the furniture and what looks appropriate, not by some random number.

[Llama]

I'd say you're doing pretty good to end up with those dimensions. Of all the walnut and cherry I've milled up in the recent weeks, I've been lucky enough to yield 1.5" from the 8/4 stock. Cut that in half, flatten it back out.. and well, you're doing pretty darn good.

Also agree about not really holding yourself to a number. 

[estesbubba]

Depends on the starting thickness also. Where I get a lot of my wood 4/4 is 15/16" hit and miss planed and never a problem getting 3/4". The hard maple I got for my Roubo was 2 1/8" hit and miss and you could have easily got two 3/4" boards from those. 

[Pwk5017]

Depends on length and trueness of your rough lumber, but i typically have 1-3/4" or 1- 7/8" finished from 8/4 rough. This is for 3-5' lengths and assuming i started with 2-1/8 or 2-1/4" material. It isnt uncommon to only get 1-5/8" when i have more twist, bow, or longer length involved. Getting two 3/4" boards out of 1-5/8" is impossible. 

 

This gets back to my other post in the lumber section about sawing thickness. If you want to have the flexibility to book match then you almost always need 8/4+. Also, maybe it is just me being wasteful, but i hate trying to squeeze thickness out of a particular board. For example, if i need 3/4-7/8 for a project, im going to be annoyed as hell if i have to work with 4/4. I would rather buy 5/4 and plane away 1/8" of waste than be extremely cute with the milling process.

[pkinneb]

Thanks all!! Some great input and tips here, ultimately I will need to reset my expectations a bit.

One point of clarification I used the term "book matched" incorrectly what I was really talking about was resawing an 8/4 board into 2 -  3/4" boards for a project. I was trying to attain good color match and grain match by using one board. The plans called for 13/16" parts for the table top and I atempted to get this out of one resawn board and as you all advised that was probably wishful thinking in the best of circumstances. Long story short I ended up with 11/16" parts which ultimately seemed to thin for the design so I will save them for another project and grabbed a 5/4 board last might and started re milling for the top.

 

[jjongsma]

13 hours ago, Sawdustdad said:

1. mill the 8/4 board straight, S4S

I'm curious about this. You suggest milling up the 8/4 board S4S before resawing. But in my experience, wood nearly always moves (at least a little bit) after re-sawing, which might result in some twist or cup in the boards. So wouldn't it make more sense to wait to do final milling until the board is done moving (i.e. after resaw)? It seems that if you mill it before resawing and then need to mill it again after resawing, you'd potentially end up losing more thickness than if you just waited to do all milling after resawing. My usual approach is get a face and edge roughly square with hand planes before resawing. But I'm curious what others do.

[Sawdustdad]

9 minutes ago, jjongsma said:

I'm curious about this. You suggest milling up the 8/4 board S4S before resawing. But in my experience, wood nearly always moves (at least a little bit) after re-sawing, which might result in some twist or cup in the boards. So wouldn't it make more sense to wait to do final milling until the board is done moving (i.e. after resaw)? It seems that if you mill it before resawing and then need to mill it again after resawing, you'd potentially end up losing more thickness than if you just waited to do all milling after resawing. My usual approach is get a face and edge roughly square with hand planes before resawing. But I'm curious what others do.

I don't know how you can accurately resaw a board that doesn't have at least two adjacent sides flat and true. I generally don't see a lot of movement after resawing but I work with air dried lumber that's been drying for 5 to 10 years or more. I suppose there is a chance that movement after resawing will make a rough board MORE true (requiring less planing) but that would be pure luck.  I don't know. but I always true up the lumber then resaw it. Generally only have to plane the one cut face.  I'd be interested in what others do in this situation...

 

 

[Eric.]

Yeah you have to have one flat face and an adjacent 90* straight edge to do any resawing, otherwise your resaw will be terrible.  No point in making the board S4S before resaw but you have to have to two flat and straight references.

[jjongsma]

Well, I do make sure that the face and edge are at 90. (I said "roughly" only because I do my milling by hand, so I only spend enough effort to make sure that the face is flat and without twist and is 90* to the edge. I don't spend a lot of time getting it perfectly smooth since it may have to be adjusted after resaw). I was mostly curious about how many people mill s4s before resawing. And as a corollary: Do most people find that their boards stay flat enough after resaw that they can leave the trued-up face alone after resaw? Or is it common for some twist to happen that requires re-milling the original reference face(s)? Maybe I'm unlucky and have been getting boards with too much internal stress, but I often find that the original face is not perfectly flat and twist-free after resawing.

I suppose it depends quite a bit on what size stock you're resawing. Thicker boards will likely move less, whereas resawing something like a 5/4 board into 2 thin boards (for small boxes, drawer sides, etc) is perhaps likely to move more.

[Eric.]

I always expect to do some milling back to flat after a resaw.  How much milling is required depends on how much the board moves.  But it's gotta be one hell of a stable board to stay perfectly flat after a resaw.

[pkinneb]

37 minutes ago, Eric. said:

I always expect to do some milling back to flat after a resaw.  How much milling is required depends on how much the board moves.  But it's gotta be one hell of a stable board to stay perfectly flat after a resaw.

I agree.