Flag union warping

For everyone who makes unions for flags what kind of clamps or cmaloing jigs are you using? I have had a few boards lately that have warped a decent bit after staining them, so when I go to cut out the design they either bow in the center or somewhere else. anyone else have this issue and know the best way to remedy this. I dont necessarily mind warping but the carving comes out uneven and that drives me crazy. Thanks for any input.

Are you similarly finishing the back of your workpiece ?

That includes stain and any other finish. Std woodworking, warps occur if you don’t do this.
Otherwise, buy extra stock and store in same area as the machine for a week or two before you either plane or size. This can help if it is atmosphere causing it.

2 Likes

Not finishing the back just the front

Try doing the back too. It doesn’t need to be pretty.
Think moisture absorption, you want both sides to be at same rate, otherwise there is warping

3 Likes

Do you think it was the staining that caused the warping or the cutting before staining?

I’ve heard this many times, but is it actually a thing? My mom has furniture from her grandmother that shows no sign of warpage and is definitely not finished on the back/inside/underside. It’s been in all sorts of climates as well.
Looking for thoughts from all the old woodworkers here (and the new ones).

1 Like

It’s true; you should treat both sides the same.

I also alternate my wood grain when I glue up a panel too.

3 Likes

This makes sense.

Quick google search turned up these which seem to contradict the belief that both sides need to be finished. I’ve been under a lot of nice dining tables…the bottoms are not finished.

https://www.woodshopnews.com/columns-blogs/finishing-both-sides-is-warped-thinking

1 Like

I’ve made actual tables myself in my own shop and I can tell you they can warp if you don’t finish both sides. They won’t alway warp but they’re much more likely to warp if you only finish one side. It’s one of the reasons that many tables have “breadboard” ends and also the tables have slotted stiffeners on them too

1 Like

I’m aware of this too. I know wood warps. I know moisture (and lack thereof) causes wood to warp. I have just heard conflicting opinions on this.

I know that internal stresses in a piece of wood will be released when it is machined.

@wb9tpg, did you see the articles I linked to?
Thanks for sharing your experiences.

I agree with Gary that if you want to glue planks to make a wide board, you need to ensure that they are properly dry, cut straight, use a jointer to remove any bend in the planks, alternate the direction of the grain for each plank.

I’m also undecided on the finish on both sides because I have a fair bit of furniture that is not finish on both sides and shows no signs of warping. On the other hand, if they are to be outside, letting moisture penetrate on one side could become an issue.

Measure a “real wood” table you have during various parts on the year. Make sure it’s a table you keep inside and it’s not an Ikea particle board table.

You’ll see the wood expands and contract across the length of the grain very little (2 or 3%). But you’ll be surprised by how much the wood expands across the width of the grain. Check out this article from Popular Woodworking

When you finish one side only the moisture enters and exits the unfinished side unimpeded. So that side expands and contracts more than the other “finished” side of the board. If you apply finish, especially water based finishes, you’re introducing moisture onto that side of the part and trigger the movement on that side only.

It’s interesting stuff but you guys can learn it yourself if you want. I’m done posting in this topic.

We have very large differences in relative humidity between summer and winter where I live from 90+% in the summer to the teens in the winter. This is very noticeable on the maple wood floor where I can get between 1/8 to 3/16in spacing between the planks in the winter and a hairline in the summer. Depending on the wood species, you get more wood movement. BTW, I did not refer to Ikea furniture but another difference may be the use of a stain, oil or other finishes that may still let moisture penetrate versus others that are mostly waterproof.

I remember in the old days where the inside of drawers on wooden sliders would start to stick in the summer, many had no finish only on the visible sides.

1 Like

I really don’t care what Popular woodworking. nor what other magazines write. I’ve SEEN wood warp when only one side is treated. Now, it might have been more Me introducing liquid that caused the expansion, but it does move…
A lot if the movement can be wood isn’t dry or you are seeing a large humidity change in short time. Again, put the wood in your shop for a week or two, then get it ready and leave it again for another week. Then machine it. internal Stress is relieved and hopefully it won’t warp on you.

See with your own eyes. You did not treat both sides the same and it warped. Different boards react differently even in the same species. Did the tree grow on a hill? There is no way to tell what will happen when finishing until you are finished. I have built hundreds of projects and a few have warped. Most do not warp but careful selection of wood grain direction helps. Most lumber is flat sawn and is subject to warping. By alternating the curvature of the tree you get the best chance of counteracting the natural process of warping. You cannot believe everything on the internet. Opinions are like butts, everyone has one and most stink.

This topic was automatically closed 30 days after the last reply. New replies are no longer allowed.