How thick should I mill?

scsmith42 · June 23, 2024, 03:06:35 PM

I mill a lot of quartersawn oak and I also make veneer. A couple of comments.

1 - when you mill oak thin, unless the grain is very consistent (even when quartersawn) you will get warpage near any grain changes. When we mill for 1/2" QS flooring, we produce 7/8" green boards that usually dry at 3/4 - 13/16", and sticker on 12" centers with around 250 PSF of weight (concrete slabs) placed on top of the stacks. For your intended purposes, I'd want either veneer grade logs or logs clear on 4 sides with 22"+ small end diameters. Definitely reverse roll QS milling pattern for the highest yield of wide, high fleck boards.

2 - Plan on 12% shrinkage in thickness (worst case) for your QSRO.

3 - Veneer that will be glued to a substrate in a vacuum bag system can have more twist, etc than thin sheets designed to be used "as is".

4 - We've had our best success when milling and drying for a 5/4 (1/8" veneer) or "fat" 6/4 (1/4" panels) thick dry board, and then resawing into the desired thickness veneer sheets. If you go this route, consistent MC% from face to face is critical. Usually the best boards for this application are the ones that have been in the inventory room for a while. Any delta in MC% from face to face will result in cupping of the resawn product. We will face joint the best face of the rough sawn board first, and then run it through a precision resaw with the blade set at the desired thickness. We keep running the board back through until we've achieved the maximum number of veneer sheets. This method produces a more consistent product thickness than dropping the head every cut. For a 1/4" finished piece we will resaw at around .300 and then sand .025 off of each face to remove the kerf marks. So our 6/4 thick board will usually produce 4 sheets of 1/4" after face jointing and resawing (our resaw kerf is only around .045)

5 - The biggest challenge to doing millwork on thin material that will not be veneered is in flattening it. Face jointing a 3/8" thick board can be a daunting challenge. If you simply plane it you may not get the cup out. That's one reason why I prefer milling thicker, drying and then resawing. This method takes more time though.

6 - If you want to try milling thin, then shoot for 1/2". It will shrink down to around 7/16" as it dries, allowing you around 3/32 per face for flattening and planning. In terms of stickering, I think that I'd try using stickers that are thinner - and narrower than usual.

burdman_22 · June 23, 2024, 08:01:16 PM

Quote from: scsmith42 on June 23, 2024, 03:06:35 PMI mill a lot of quartersawn oak and I also make veneer. A couple of comments.

1 - when you mill oak thin, unless the grain is very consistent (even when quartersawn) you will get warpage near any grain changes. When we mill for 1/2" QS flooring, we produce 7/8" green boards that usually dry at 3/4 - 13/16", and sticker on 12" centers with around 250 PSF of weight (concrete slabs) placed on top of the stacks. For your intended purposes, I'd want either veneer grade logs or logs clear on 4 sides with 22"+ small end diameters. Definitely reverse roll QS milling pattern for the highest yield of wide, high fleck boards.

2 - Plan on 12% shrinkage in thickness (worst case) for your QSRO.

3 - Veneer that will be glued to a substrate in a vacuum bag system can have more twist, etc than thin sheets designed to be used "as is".

4 - We've had our best success when milling and drying for a 5/4 (1/8" veneer) or "fat" 6/4 (1/4" panels) thick dry board, and then resawing into the desired thickness veneer sheets. If you go this route, consistent MC% from face to face is critical. Usually the best boards for this application are the ones that have been in the inventory room for a while. Any delta in MC% from face to face will result in cupping of the resawn product. We will face joint the best face of the rough sawn board first, and then run it through a precision resaw with the blade set at the desired thickness. We keep running the board back through until we've achieved the maximum number of veneer sheets. This method produces a more consistent product thickness than dropping the head every cut. For a 1/4" finished piece we will resaw at around .300 and then sand .025 off of each face to remove the kerf marks. So our 6/4 thick board will usually produce 4 sheets of 1/4" after face jointing and resawing (our resaw kerf is only around .045)

5 - The biggest challenge to doing millwork on thin material that will not be veneered is in flattening it. Face jointing a 3/8" thick board can be a daunting challenge. If you simply plane it you may not get the cup out. That's one reason why I prefer milling thicker, drying and then resawing. This method takes more time though.

6 - If you want to try milling thin, then shoot for 1/2". It will shrink down to around 7/16" as it dries, allowing you around 3/32 per face for flattening and planning. In terms of stickering, I think that I'd try using stickers that are thinner - and narrower than usual.

Thank you for the thorough response. 1/2" sounds good to me, I think that's what I will try. I'd planned on using much smaller stickers than normal...if anything it will slow drying down, which will be beneficial I think for this thin stuff.

The log I'm using is clear on all sides, and the pith is centered, so I'm hoping for very little stress in the log. The small end of the log is about 28 inches, so I should have plenty of log.

This is mostly an experiment...and attempt to save my buddy some processing time. Only a few boards from the lig will be going to him, as he doesn't need more than a few boards. Everything else I'm the log I'll mostly be milling into 1x6s

scsmith42 · June 24, 2024, 09:15:55 AM

Sounds like a good plan.

carpet56238 · June 24, 2024, 09:58:48 AM

For quartersawn red oak, you'll definitely see some shrinkage due to moisture loss as it dries out. Usually, wood can lose around 10-15% of its thickness during drying, so if you aim for 1/4 inch thick stock, starting around 5/16 to 3/8 inch thick might be a good bet.