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Dealing with Twist

#259974 by algale » Mon May 27, 2019 6:21 am

How does one take the twist out of a board? These are about 50" inches long, 4" wide, and 2" thick. They are significantly twisted, maybe 1/8th" rock from side to side. I can't shorten them for this project.

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Gale's Law: The bigger the woodworking project, the less the mistakes show in any photo taken far enough away to show the entire project!

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Re: Dealing with Twist

#259975 by garys » Mon May 27, 2019 6:38 am

If you have enough thickness of wood to plane them until they are perfectly straight, my only other option seems to be to use them as firewood.

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Re: Dealing with Twist

#259976 by BuckeyeDennis » Mon May 27, 2019 6:41 am

What do you need the finished dimensions to be?

That size board isn’t too bad to flatten on a SS jointer, as long as the finish width is under 4”. I just try to start the first pass at about mid-rock, so as take roughly equal amount of thickness off of the opposite corners.

If the board is over 4” wide, or if I have barely enough thickness to get it flat, I use a Thien planer sled. Quick and easy — all you need is a hot-glue gun, some wide masking tape, and a flat board. I usually use a piece of melamine shelving for the latter. You can tweak the workpiece rock angle while the hot glue sets up.

http://www.jpthien.com/ps.htm

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Re: Dealing with Twist

#259978 by algale » Mon May 27, 2019 6:49 am

I should have specified I have a 6" jointer.

The finished width only needs to be about 2" wide by 1" thick by 50" long.

So the technique on the jointer is to start in the middle, pressure on the high edge, then rotate and middle to end with pressure on opposite high edge? That makes sense, Dennis, thanks.

I've read about the Thien method but never tried it. Now is maybe the time.

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Gale's Law: The bigger the woodworking project, the less the mistakes show in any photo taken far enough away to show the entire project!

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Re: Dealing with Twist

#259980 by BuckeyeDennis » Mon May 27, 2019 7:09 am

I would actually joint that board from the end, holding it at about mid-rock to start the cut. As soon as the first-cut corner makes it onto the outfeed table, the rock angle will be stable. You have plenty of material, though, so the initial rock angle doesn’t really matter.

More importantly, rough-cutting to width first will effectively eliminate almost half of the twist before you even start jointing. I’d rip it on the bandsaw down to maybe 2-1/2” wide while still rough. That will help relieve any internal stresses, which could cause it to re-twist if ripped after flattening. And as that board is already twisted, it’s a good bet that it has significant internal stresses.

As Charles Neil preaches: “Sneak up on it!” The final dimensions, that is. For the most stable workpiece, you want your final milling to be done from near-final dimensions, and after the wood has had a chance to rest/relax for a few days at near-final dimensions.

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Re: Dealing with Twist

#259985 by RFGuy » Mon May 27, 2019 8:13 am

I never saw the Thien planer sled before. There is also the fancy one that was written up in ShopNotes (link below). I have been meaning to build one of these because I have do deal with twisty lumber a good bit. I'll have to review this Thien method a bit more as an alternative.

https://www.shopnoteslibrary.com/view/issue/137/#page=1

https://www.youtube.com/watch?v=XrUcHUqTSyM

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Re: Dealing with Twist

#259986 by ChrisNeilan » Mon May 27, 2019 8:43 am

BuckeyeDennis wrote:I would actually joint that board from the end, holding it at about mid-rock to start the cut. As soon as the first-cut corner makes it onto the outfeed table, the rock angle will be stable. You have plenty of material, though, so the initial rock angle doesn’t really matter.

More importantly, rough-cutting to width first will effectively eliminate almost half of the twist before you even start jointing. I’d rip it on the bandsaw down to maybe 2-1/2” wide while still rough. That will help relieve any internal stresses, which could cause it to re-twist if ripped after flattening. And as that board is already twisted, it’s a good bet that it has significant internal stresses.

As Charles Neil preaches: “Sneak up on it!” The final dimensions, that is. For the most stable workpiece, you want your final milling to be done from near-final dimensions, and after the wood has had a chance to rest/relax for a few days at near-final dimensions.


Absolutely the way to go!

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Chris Neilan

Shopsmith Mark 7, Shopsmith Mark V 1982, shortened, Shopsmith 10 ER; Craftsman table saw (1964); Powermatic 3520B lathe

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Re: Dealing with Twist

#259991 by BuckeyeDennis » Mon May 27, 2019 12:39 pm

RFGuy wrote:I never saw the Thien planer sled before. There is also the fancy one that was written up in ShopNotes (link below). I have been meaning to build one of these because I have do deal with twisty lumber a good bit. I'll have to review this Thien method a bit more as an alternative.

https://www.shopnoteslibrary.com/view/issue/137/#page=1

https://www.youtube.com/watch?v=XrUcHUqTSyM


That ShopNotes sled looks like quite a project itself! I would consider something like that if I did a whole lot of wide-board flattening — no way am I ever going to get a 12” jointer into my basement shop! But that design looks like the sled itself would use up about all of the 4” thickness capacity of my Shopsmith planer.

The Thein sled, on the other hand, needs only about a 3/4” board as a base, so I can flatten rough stock up to about 3” thick. Once you make the “sandwich” with masking tape and hot glue, the entire assembly is very rigid. But if you are using a thin base, you do need to make up the sandwich on a flat surface, so that the base board stays flat.

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Re: Dealing with Twist

#259992 by RFGuy » Mon May 27, 2019 12:44 pm

BuckeyeDennis wrote:That ShopNotes sled looks like quite a project itself! I would consider something like that if I did a whole lot of wide-board flattening — no way am I ever going to get a 12” jointer into my basement shop! But that design looks like the sled itself would use up about all of the 4” thickness capacity of my Shopsmith planer.

The Thein sled, on the other hand, needs only about a 3/4” board as a base, so I can flatten rough stock up to about 3” thick. Once you make the “sandwich” with masking tape and hot glue, the entire assembly is very rigid. But if you are using a thin base, you do need to make up the sandwich on a flat surface, so that the base board stays flat.

Yeah, I agree. When I came across the ShopNotes one, I saved it to consider for later...still haven't built it yet. It would have to be scaled down for it to be usable on a Shopsmith planer. The Thien sled would probably work better. The other option is to use hand planes to rough surface one side and then flip it over and run it through the planer to square it up.

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Re: Dealing with Twist

#259994 by jsburger » Mon May 27, 2019 12:55 pm

ChrisNeilan wrote:
BuckeyeDennis wrote:I would actually joint that board from the end, holding it at about mid-rock to start the cut. As soon as the first-cut corner makes it onto the outfeed table, the rock angle will be stable. You have plenty of material, though, so the initial rock angle doesn’t really matter.

More importantly, rough-cutting to width first will effectively eliminate almost half of the twist before you even start jointing. I’d rip it on the bandsaw down to maybe 2-1/2” wide while still rough. That will help relieve any internal stresses, which could cause it to re-twist if ripped after flattening. And as that board is already twisted, it’s a good bet that it has significant internal stresses.

As Charles Neil preaches: “Sneak up on it!” The final dimensions, that is. For the most stable workpiece, you want your final milling to be done from near-final dimensions, and after the wood has had a chance to rest/relax for a few days at near-final dimensions.


Absolutely the way to go!


I totally agree. That is exactly the way I would do it and have hundreds of times.

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John & Mary Burger
Eagle's Lair Woodshop
Hooper, UT

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